Disc brake front wheel ejection: fact or fantasy?
Doug Taylor
are going at it once again on this subject, with the tech heads and
roadies basically saying that you are taking your life in your hands
if you use disc brakes with QR's and regular dropouts on the theory
that the QR eventually will come loose under force of the front brake
and your wheel will pop off.
So, my question is: has anybody who actually rides mountain bike with
any frequency (such as the amb crowd) experienced this phenomenon or
heard of anybody loosing a wheel? If so, any serious injuries? Is
the sky really falling or can we get back on our bikes and ride?
--dt
John Morgan
> any frequency (such as the amb crowd) experienced this phenomenon or
> heard of anybody loosing a wheel? If so, any serious injuries? Is
> the sky really falling or can we get back on our bikes and ride?
I would like to offer the first response to this question. I think the QR
scare is bollocks. A simple look at ratios can tell you that out of the
millions of riders with the disc brake/QR setup, there are only one or two
documented cases of it happening. Crashes happen every day due to equipment
failure and rider error... moreso the latter. There's nothing to get
excited about here, folks.
-John Morgan
The Nelson Paradigm
news:7107lv83bggi8ed3l...@4ax.com...
Don't own a Disc myself, but none of my customers have ever had this kind of
problem. Granted, we don't have really long downhill courses in NC.
I think the whole thing is a bunch of hogwash. Every single picture I've
ever seen looks a lot more like a mis-adjusted skewer to me.
---
__o
_`\(,_ Cycling is life,
(_)/ (_) all the rest, just details.
The Nelson Paradigm =^o.o^=
http://intergalax.com
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.512 / Virus Database: 309 - Release Date: 8/19/2003
bomba
> So, my question is: has anybody who actually rides mountain bike with
> any frequency (such as the amb crowd) experienced this phenomenon or
> heard of anybody loosing a wheel? If so, any serious injuries? Is
> the sky really falling or can we get back on our bikes and ride?
Do you remember a guy posting here called Russ Pinder? Well, he's
currently in a wheelchair.
Super Slinky
> Do you remember a guy posting here called Russ Pinder? Well, he's
> currently in a wheelchair.
But the web site in his honor says that the cause of the crash can never
be known. Besides that, even if it was wheel ejection that caused his
crash details are lacking. What fork was he using? Was it one of those
Pace forks that don't have retention lips? Maybe the skewer just broke.
Maybe the dropouts broke off the lower legs.
deluxe model
"Super Slinky" <sli...@newmail.net> wrote in message
news:MPG.19bd6a9b9...@netnews.comcast.net...
Super Slinky
> Do you check/tighten your skewers before every ride? I certainly do.
I don't, but I probably should. I switched to non-quick release skewers
about a month ago. I always considered quick release to be a solution to
a problem I never had. It's no big deal to carry an allen wrench and it
makes it tougher for a thief to steal your wheels. Don't have QR on my
seat collar either.
Westie
Most likely more than half of the people out there that ride 'mountain
bikes' have never heard of this issue and wouldn't know where to find a
'quick release skewer' on their bikes if they had to. Many of the pure
recreational riders and Dewbies that I know just aren't interested in
regular equipment checks. They'll check it if it happens, otherwise
ignorance is bliss and they'll ride it 'til it breaks.
With so many amateur riders out there it's amazing that front wheels aren't
falling off left, right and centre. And not from braking forces - just from
lack of proper adjustment.
--
Westie
mule
> bikes' have never heard of this issue and wouldn't know where to find
> a 'quick release skewer' on their bikes if they had to. Many of the
> pure recreational riders and Dewbies that I know just aren't
> interested in regular equipment checks. They'll check it if it
> happens, otherwise ignorance is bliss and they'll ride it 'til it
> breaks.
>
> With so many amateur riders out there it's amazing that front wheels
> aren't falling off left, right and centre. And not from braking
> forces - just from lack of proper adjustment.
You really think so?
I get a bit paranoid about my QR skewers and check them before every ride.
I also check my headset before every ride, though that didn't stop it
getting loose on my last run.
I think it may be the way I ride - everything seems to come loose on my
bike. I've had the saddle come loose once too.
Last thing I want to be doing is eating my steering tube for breakfast...
--
...meandering mule...
Alex Bird
>
> So, my question is: has anybody who actually rides mountain bike with
> any frequency (such as the amb crowd) experienced this phenomenon or
> heard of anybody loosing a wheel? If so, any serious injuries? Is
> the sky really falling or can we get back on our bikes and ride?
I saw a tv programme 3-4 years ago here in the uk, about a kid in the
west-country (SW England). His front wheel came loose and _somehow_
the forks ended up in the back of his skull. They showed the x-rays,
a few more millimetres and he would have been dead. Yes, he was fine,
after some medical attention. I think I've checked my quick release
every time I've got on my bike since I saw that...
Why would discs be more likely to release the wheel? This makes no
sense to me.
Alex
bomba
>>Do you remember a guy posting here called Russ Pinder? Well, he's
>>currently in a wheelchair.
>
>
> But the web site in his honor says that the cause of the crash can never
> be known.
True, I don't think anybody will ever know for certain exactly what
happened. However, he and his friends are under the impression that the
disc / dropout phenomenon exerted itself on that day.
> Besides that, even if it was wheel ejection that caused his
> crash details are lacking.
What details? The tribute website is not there to debate the causes of
the accident, nor comment on the disc / dropout issue.
What fork was he using? Was it one of those
> Pace forks that don't have retention lips?
No. He'd actually swapped from a set of Pace for exactly this reason.
He was riding Fox forks, I believe.
bomba
> This is my first post to this group, sorry it's a bit grim.
> I saw a tv programme 3-4 years ago here in the uk, about a kid in the
> west-country (SW England). His front wheel came loose and _somehow_
> the forks ended up in the back of his skull. They showed the x-rays,
> a few more millimetres and he would have been dead. Yes, he was fine,
> after some medical attention. I think I've checked my quick release
> every time I've got on my bike since I saw that...
Not quite the same thing. He popped a wheelie off a kerb, the wheel
fell out, chucked him over the bars and the bike then somersaulted in to
his head. Bet he couldn't do that again if he tried :)
> Why would discs be more likely to release the wheel? This makes no
> sense to me.
How technical do you want to get?
http://www.kinetics.org.uk/html/disc_brakes___qrs.html
bomba
> This is my first post to this group, sorry it's a bit grim.
> I saw a tv programme 3-4 years ago here in the uk, about a kid in the
> west-country (SW England). His front wheel came loose and _somehow_
> the forks ended up in the back of his skull. They showed the x-rays,
> a few more millimetres and he would have been dead. Yes, he was fine,
> after some medical attention. I think I've checked my quick release
> every time I've got on my bike since I saw that...
Not quite the same thing. He popped a wheelie off a kerb, the wheel
fell out, chucked him over the bars and the bike then somersaulted in to
his head. Bet he couldn't do that again if he tried :)
That was from 999, and was way longer than 3 or 4 years ago.
> Why would discs be more likely to release the wheel? This makes no
> sense to me.
How technical do you want to get?
http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/
Westie
"mule" <meandering...@nospam.breathe.com> wrote in message
news:3f53bf7f$1...@news1.homechoice.co.uk...
> > With so many amateur riders out there it's amazing that front wheels
> > aren't falling off left, right and centre. And not from braking
> > forces - just from lack of proper adjustment.
>
> You really think so?
> I get a bit paranoid about my QR skewers and check them before every ride.
> I also check my headset before every ride, though that didn't stop it
> getting loose on my last run.
I think that anyone that posts here is probably taking a bit more interest
in their bike and the bike's maintenance.
Sure, your headset came loose but you identified and remedied the problem.
You didn't ride it until it came apart.
Was it someone here that had the tagline "You can't make anything
foolproof - the fools are too inventive"? I think it applies to some
degree.
>
> I think it may be the way I ride - everything seems to come loose on my
> bike. I've had the saddle come loose once too.
Any piece of equipment needs adjustment from time to time to keep it both
safe and well tuned.
But there are riders out there that just ride until something major falls
off - and if it's the QR coming loose because it hasn't been checked - ever,
then you've got a problem. I'm not saying that they're careless or
incompetant, it's just never something that occurs to them. They consider
the worst thing that can happen to them is a puncture or maybe 'changing
gear' problems. Maintenance is a bit of oil on the chain. It's never
occurred to them that a wheel might fall off.
--
Westie
Spider
I believe that an analysis of the accident says the cause for the
wheel ejection was not knon, and might never be known. Without
knowing the initial conditions, nor having any analysis done on the
fork post-crash, I don't think anyone will ever know exactly how it
happened.
Spider
Mike Kennedy
lawyer tabs kept the wheel from coming all the way out and it was an
interesting ride feel until I got stopped. I was bombing some very washboard
single track at the time. It has only happened the one time. I am pretty
diligent about making sure that when put the front wheel on that I have it
tight, so I do not think that this was the problem. Who knows.
This has never happened on any of my other bikes, present or past that
have "regular" brakes.
Mike
"Doug Taylor" <tayl...@choiceonemail.com> wrote in message
news:7107lv83bggi8ed3l...@4ax.com...
Monique Y. Herman
>
>
> Any piece of equipment needs adjustment from time to time to keep it both
> safe and well tuned.
> But there are riders out there that just ride until something major falls
> off - and if it's the QR coming loose because it hasn't been checked - ever,
> then you've got a problem. I'm not saying that they're careless or
> incompetant, it's just never something that occurs to them. They consider
> the worst thing that can happen to them is a puncture or maybe 'changing
> gear' problems. Maintenance is a bit of oil on the chain. It's never
> occurred to them that a wheel might fall off.
> --
> Westie
>
I specifically asked a LBS about bike maintenance classes, and
the salesguy claimed that he knew of no such thing in the area. As my
fiance seems to have a handle on the maintenance thing, I haven't gone
looking too hard, but, jeez! The LBS guy acted like it should all be common
sense ... and maybe it should ... but I've never assembled or maintained
anything mechanical, aside from putting parts into a computer, where all
moving parts are carefully hidden from the user. I know enough to know
that I don't know what I'm doing when it comes to bikes (cars, lawn
mowers, garbage disposals, spigots ...).
At least mounting the bike on the car every trip means I have to make
sure my front tire is properly positioned before riding off ... and
after having an issue with my brakes at the beginning of one trip
(something about the end of the wire near the handlebars coming out of
position), I do test both front and rear brakes before going anywhere.
--
monique
(Pete Cresswell)
> I switched to non-quick release skewers
>about a month ago. I always considered quick release to be a solution to
>a problem I never had. It's no big deal to carry an allen wrench and it
>makes it tougher for a thief to steal your wheels. Don't have QR on my
>seat collar either.
Where did you get them? I'd like to get a set just because the levers on mine
are so hard to open up when the wheel needs removing...
-----------------------
PeteCresswell
(Pete Cresswell)
>Why would discs be more likely to release the wheel?
Something about the direction of forces infolved when the calipers grab the
disk. I can't put it into words, but after reading the discussions here I can
visualize it easily. One clue: if the calipers were in front of the hub
instead of behind, there wouldn't be a problem.
-----------------------
PeteCresswell
(Pete Cresswell)
>With so many amateur riders out there it's amazing that front wheels aren't
>falling off left, right and centre. And not from braking forces - just from
>lack of proper adjustment.
I don't check mine either - but I think there's a fallacy in the "..we haven't
heard anything about it, so it must not be happening...." line of thinking.
Nobody's doing post-crash analysis' of bike accidents like the FAA does in
airplane crashes and people who get greviously injured probably don't broadcast
it to the world. More likely, they just sort of fade away from the biking
world...
Bottom line for me is that nobody really knows - qualified by the observation
that there hasn't yet been a legal feeding frenzy involving fork makers, which
has to count for something considering the litigiousness (sp?) of the current
release of USA.
-----------------------
PeteCresswell
Super Slinky
> Where did you get them? I'd like to get a set just because the levers on mine
> are so hard to open up when the wheel needs removing...
> -----------------------
> PeteCresswell
Nashbar. There is a category for skewers. They're nothing fancy, but
they get the job done. I don't miss QR at all.
Chris Hughes
falling off left, right and centre"
looking to buy a new bike. At a well regarded bike shop I was going to test
ride a bike, the salesmen adjusted the seat and then gave the bike to the
mechanic to check before I took it out. I don't know what he checked
because the quick release on the front brake was open and with it open did
not contact the rim enough to stop the bike. I tried to brake at a stop
sign and no front brake. A car very nearly hit me as I crossed the highway.
It was a very vivid lesson in who is responsible to check a bike before it
is ridden. Check the brakes, check the skewers, bounce the bike and see
what shakes, check the handle bars and seats to see there tight. That
should take about 15 sec if every thing is ok and may be life saver if they
are not
Chris
"Westie" <Wes...@invalid.address.null> wrote in message
news:bj0bik$3mk$1...@lust.ihug.co.nz...
gabrielle
> Not quite the same thing. He popped a wheelie off a kerb, the wheel
> fell out, chucked him over the bars and the bike then somersaulted in to
> his head. Bet he couldn't do that again if he tried :)
>
> That was from 999, and was way longer than 3 or 4 years ago.
I don't think they had disk brakes back then. ;)
gabrielle
gabrielle
> I specifically asked a LBS about bike maintenance classes, and the
> salesguy claimed that he knew of no such thing in the area.
Check your local community ed. Oh yeah, and other bike shops, assuming
you have them. ;) Stuff like adjusting your brakes and derailleur aren't
that difficult once you know where the screws are.
I've heard good things about _Zinn and the Art of Mt Bike Maintenance_,
but can't vouch for it myself as I haven't found a copy yet.
And there's always Sheldon "Hottie" Brown's website:
http://www.sheldonbrown.com/harris/index.htm
HTH
gabrielle
Super Slinky
> Why would discs be more likely to release the wheel? This makes no
> sense to me.
>
> Alex
There is a theory, conjured by one person by the name of James Annan,
who rides a tandem mountain bike, and a few roadies who don't ride
mountain bikes at all, that repeated use of the disc brake loosens the
skewer, and when the skewer is loose enough, the brake ejects the wheel
out of the dropout. There have been no documented cases of it ever
having actually happened to anyone, except to maybe James Annan himself.
Myself, Doug Taylor and Spider have been the main people taking the
skeptical side of the debate over in rec.bicycles.tech. James Annan
wants to attribute every wheel loss, and seemingly every off-road biking
injury, to his pet theory. He is quite close-minded to any opposing
viewpoint. I believe that it actually happened to him, but his was a
very special case. He was on a tandem which can exert extreme forces in
braking, much more than you would see on a single person bike. Worse,
his fork was very poorly designed. It almost looked like it was built to
have this failure. It had no retention lips and this feature alone would
have almost certainly prevented the wheel from going anywhere. The fork
also had a very odd dropout angle that slanted toward the rear and ran
parallel with the brake rotor. Vertical dropouts would have resisted
some of the ejection force.
Now he is badgering bicycle manufacturers, journalists and the American
Consumer Product Safety Commission, not to mention us on the Internet,
that something must be done about it. The fact that almost nobody who
actually uses bikes so equipped believes him or takes his scare tactics
seriously doesn't faze him in the least. My opinion is that retention
lips make this failure almost impossible. This opinion is backed up by
the fact that nobody can find any cases of it happening to anyone but
him. His bike didn't have them, the vast majority of bike sold in the US
do and have for years. Europe may be different.
Super Slinky
Oh yeah. William the Conqueror defeated King Harold at the Battle of
Hastings riding mountain bikes.
Monique Y. Herman
Thanks for the pointers. I have to admit to being a bit wary of
shifters -- I tried to "tune" the gears on a bike I had while in college
on the theory of, "How complicated could this possibly be?" ...
Needless to say, with no knowledge whatsoever, that bike never shifted
properly again.
The best way to deal with a fear is to meet it head-on, though, right?
--
monique
John Harlow
> the salesguy claimed that he knew of no such thing in the area.
Often times, shops have 3 increasing labor rates:
1 - the regular hourly rate,
2 - the rate if you watch,
3 - the rate if you help ;)
Seriously though, maybe they can get a tech to go over basic adjustments
with you on your bike.
JD
> The boys (the girls are too sensible, it seems) in rec.bicycles.tech
> are going at it once again on this subject, with the tech heads and
> roadies basically saying that you are taking your life in your hands
> if you use disc brakes with QR's and regular dropouts on the theory
> that the QR eventually will come loose under force of the front brake
> and your wheel will pop off.
Roadies and especially the bunch at rectum.bisexual.techsticles are a
bunch of sissy punkasses.
JD
James Annan
> There is a theory, conjured by one person by the name of James Annan,
> who rides a tandem mountain bike, and a few roadies who don't ride
> mountain bikes at all, that repeated use of the disc brake loosens the
> skewer, and when the skewer is loose enough, the brake ejects the wheel
> out of the dropout.
> The fact that almost nobody who
> actually uses bikes so equipped believes him or takes his scare tactics
> seriously doesn't faze him in the least.
The fact that trolls like yourself lie about me on usenet certainly
doesn't faze me in the least. I'm not stupid and I realised right from
the start that with so many powerful vested interests involved I was
going to end up the scapegoat anyway, it's tough shit but that's what
whistleblowers have always got for their trouble. I don't want it to
be _my_ campaign but neither am I prepared to sit back and do nothing
while the manufacturers stick their heads in the sand and riders
continue to get seriously hurt by this design fault.
Several of the journalists who have written about this (and who all
agree that there is a real problem, having reviewed the ample evidence
in its favour) are in fact trained engineers with long experience in
the bicycle industry, and some of the most respected expert witnesses
in bicycle liability litigation bar none (also trained engineers) have
stated their clear opinion that there is a dangerous fault. Many
people have now replicated the phenomenon by themselves, no special
equipment required, and it is increasingly ridiculous that the
manufacturers pretend they don't know about it. Some people who work
in the industry, who know for sure there is a problem, have stated
that they don't want bodies such as the CPSC involved precisely
because they _do_ know there is a real problem, and it's going to cost
someone quite a lot of money to fix.
Of course, the longer this drags on, the more it will cost when it
eventually does get fixed. But you'd rather attack me than actually
ask the manufacturers for some answers. That says plenty about your
motivation and interest in this problem. Never mind, it will
eventually be solved, but it will be despite your contribution rather
than with the help of it. You may think you are saving the
manufacturers from unnecessary interference, but you are actually
encouraging them to dig their own graves. I hope you are proud of
yourself.
James
spademan o---[) *
"Doug Taylor" <tayl...@choiceonemail.com> wrote in message
news:7107lv83bggi8ed3l...@4ax.com...
> The boys (the girls are too sensible, it seems) in rec.bicycles.tech
> are going at it once again on this subject, with the tech heads and
> roadies basically saying that you are taking your life in your hands
> if you use disc brakes with QR's and regular dropouts on the theory
> that the QR eventually will come loose under force of the front brake
> and your wheel will pop off.
>
> any frequency (such as the amb crowd) experienced this phenomenon or
> heard of anybody loosing a wheel? If so, any serious injuries? Is
> the sky really falling or can we get back on our bikes and ride?
>
There has been much discussion over this issue on singletrackworld.com, not
surprising really as the issue is very close to some of the regulars. As far
as I can tell there has been no conclusive proof either way, although some
independant testing has shown that vibration from disc brake forces can lead
to a loosening of the Q.R. nut the testing has not been rigerous enough to
draw a verifiable conclusion. I believe its an issue that should continue to
be discussed. Just because it hasn't happened to you, or to anyone you know
doesn't mean it can't happen.
A bodge solution was put forward on the STW forum:
http://www.singletrackworld.com/forum/read.php?f=2&i=528933&t=528093#reply_5
28933
basically it involves using a jubilee clip (hose clamp) to clamp round the
Q.R. nut with the jubilee nut resting against the fork dropouts, resisting
loosening.
If anyone is really interested there are a few more interesting discussions
on the following threads:
http://www.singletrackworld.com/forum/read.php?f=2&i=526529&t=523608#reply_5
26529
http://www.singletrackworld.com/forum/read.php?f=2&i=533475&t=531565#reply_5
33475
http://www.singletrackworld.com/forum/read.php?f=2&i=554322&t=553505#reply_5
54322
Steve.
spademan o---[) *
Thats fine to stop thieves but if anything it will worsen the loosening
problem. The Q.R. lever effectively prevents that end of the Q.R. from
loosening as it would interfere with the fork legs. When tested
Shaun Rimmer
Doug Taylor <tayl...@choiceonemail.com> wrote in message
news:7107lv83bggi8ed3l...@4ax.com...
> The boys (the girls are too sensible, it seems) in rec.bicycles.tech
> are going at it once again on this subject, with the tech heads and
> roadies basically saying that you are taking your life in your hands
> if you use disc brakes with QR's and regular dropouts on the theory
> that the QR eventually will come loose under force of the front brake
> and your wheel will pop off.
>
> So, my question is: has anybody who actually rides mountain bike with
> any frequency (such as the amb crowd) experienced this phenomenon or
> heard of anybody loosing a wheel? If so, any serious injuries? Is
> the sky really falling or can we get back on our bikes and ride?
Well, I got a Hope Mini on the front, with the big rotor, bike is heavy and
so is my pack. Big bad grippy knobbies, and I don't half hammer on that
brake lever some times when coming to a stop - _never_ had a problem, not
slight, not at all, never. I do get _very_ medieval on my QR skewers though
(closed 'em with my feet before now......), enough that I'm worried for the
life of my dropouts, heheheheh..........
This is my own experience only, obverously.
Shaun aRe
spademan o---[) *
"Shaun Rimmer" <sh...@newtronic.co.uk> wrote in message
news:bj1nhr$dq3nv$1...@ID-170198.news.uni-berlin.de...
> > So, my question is: has anybody who actually rides mountain bike with
> > any frequency (such as the amb crowd) experienced this phenomenon or
> > heard of anybody loosing a wheel? If so, any serious injuries? Is
> > the sky really falling or can we get back on our bikes and ride?
>
> Well, I got a Hope Mini on the front, with the big rotor,
Strangely smaller rotors are thought to be worse as the angle of braking
force is aligned more closely with the dropout angle.
> bike is heavy and
> so is my pack.
But you're a skinny lad like me so it evens out. I don't think this is a
factor though.
> Big bad grippy knobbies, and I don't half hammer on that
> brake lever some times when coming to a stop - _never_ had a problem, not
> slight, not at all, never. I do get _very_ medieval on my QR skewers
though
> (closed 'em with my feet before now......), enough that I'm worried for
the
> life of my dropouts, heheheheh..........
Seems like the most sensible thing to do for now.
> This is my own experience only, obverously.
>
> Shaun aRe
>
Steve.
Alex Bird
> Not quite the same thing. He popped a wheelie off a kerb, the wheel
> fell out, chucked him over the bars and the bike then somersaulted in to
> his head. Bet he couldn't do that again if he tried :)
I'm willing to bet he hasn't tried.
> That was from 999, and was way longer than 3 or 4 years ago.
Nah, twas no more than five years ago, I remember where I was when I saw it.
Westie
"Monique Y. Herman" <mon...@bounceswoosh.org> wrote in message
news:vl7v993...@corp.supernews.com...
> > And there's always Sheldon "Hottie" Brown's website:
> > http://www.sheldonbrown.com/harris/index.htm
> >
> > HTH
> > gabrielle
>
> Thanks for the pointers. I have to admit to being a bit wary of
> shifters -- I tried to "tune" the gears on a bike I had while in college
> on the theory of, "How complicated could this possibly be?" ...
> Needless to say, with no knowledge whatsoever, that bike never shifted
> properly again.
>
> The best way to deal with a fear is to meet it head-on, though, right?
> --
> monique
It really is a case of sitting down with the bike one day and deciding "Hey!
How bad can I really mess this up? I'm not fixing it with what I'm doing
now!". Then just doing it and twisting everything right across the range
from one stop to the other stop and carefully watching the resulting
movement in the mechanism and the consequences. Tentative and delicate
adjustments in an attempt to fix the problem without making it worse only
confuse you. You don't see any measurable result and don't really understand
or know what you've adjusted.
--
Westie
...well, at least that's what I did...
Westie
"(Pete Cresswell)" <x@y.z> wrote in message
news:9on7lvoo0ofhduum4...@4ax.com...
I certainly agree with you - nobody really knows for sure. I'm not really
arguing whether or not there is a problem with disc brakes. I think that
there is. But I'm inclined to believe that it stems from incorrectly
adjusted equipment in the first place. It'll only happen if the axle is
loose enough to move under a moderate downwards force. That should only
happen if the QR and skewer is adjusted incorrectly.
If you look at the brakes and the forces involved it's reasonably obvious
that discs make a loose skewer more likely to pop out than other types of
brakes. How much more likely? Who knows? That's the problem. All I know
is that if I was braking and had a very loose QR then I would not want that
front wheel to get ANY air under it. The moment that wheel has the
opportunity to move downwards while the disc calipers are clamped on that
rotor the torque will twist that wheel down and out! It's not a matter of
it 'falling out' due to gravity. It'll be pushed out with force while under
braking.
Anyway, the initial problem is that the QR was loose in the first place and
that's just asking for an accident to happen - discs or no discs. The disc
brakes only exacerbate an existing fault, IMO. It'll be interesting to see
how the issue develops and what, if any, changes are made to fork design.
--
Westie
Michael Dart
> are going at it once again on this subject, with the tech heads and
> roadies basically saying that you are taking your life in your hands
> if you use disc brakes with QR's and regular dropouts on the theory
> that the QR eventually will come loose under force of the front brake
> and your wheel will pop off.
>
> any frequency (such as the amb crowd) experienced this phenomenon or
> heard of anybody loosing a wheel? If so, any serious injuries? Is
> the sky really falling or can we get back on our bikes and ride?
>
A local ski resorts new rental fleet came with Marzocchi Dirt Jumper 3 forks
that had this problem. You could lock the front brake and push the bike
forward and the axle would pop out. I didn't get a close enough look at the
skewer or the dropouts but was told they were made without 'lawyer lips'.
Marzocchi had to replace all the lowers on the forks with their Z1 lowers.
I think the DJ 3 is one of their forks now being made in Taiwan. As for my
friends and I, we have never had a problem with discs and QR forks. I have
Hope Mini's mounted on a Marzocchi Marathon fork.
Mike
bomba
>>That was from 999, and was way longer than 3 or 4 years ago.
>
>
> Nah, twas no more than five years ago, I remember where I was when I saw it.
Well you can't remember that well, because you've already limited it to
a period of two years...
Maybe you saw the repeat, but it was featured in one of the earlier
episodes of 999. 999 began in '92.
--
a.m-b FAQ: http://www.t-online.de/~jharris/ambfaq.htm
a.bmx FAQ: http://www.t-online.de/~jharris/bmx_faq.htm
mjm
"Doug Taylor" <tayl...@choiceonemail.com> wrote in message
news:7107lv83bggi8ed3l...@4ax.com...
> The boys (the girls are too sensible, it seems) in rec.bicycles.tech
> are going at it once again on this subject, with the tech heads and
> roadies basically saying that you are taking your life in your hands
> if you use disc brakes with QR's and regular dropouts on the theory
> that the QR eventually will come loose under force of the front brake
> and your wheel will pop off.
>
> So, my question is: has anybody who actually rides mountain bike with
> any frequency (such as the amb crowd) experienced this phenomenon or
> heard of anybody loosing a wheel? If so, any serious injuries? Is
> the sky really falling or can we get back on our bikes and ride?
>
> --dt
Do a search to see how many law suits have been filed in the US. Lets face
it, major bike manufacturers have been selling disc brakes with QR wheels
for quite a few years now. If the case of occurrence was that high, there
would be at least 10-20 law suits in process right now.
As well, you must consider, if this is such a prevalent thing, new bikes
would be re-designed to stop this phenomenon before they left the factory
floor. You have to look at any number of issues with the wheel coming off
the bike from disc pressure. What is the tensile strength of the skewer,
and stretch factor of the metal used. Compression on the QR ends that could
effect the static friction that holds the wheel onto the front fork. The
design on the fork. Was there any contamination on the contact points. (ie
grease or other foreign materials). The list goes on and on.
Lets face it. If it was a major concern then it would be on Dateline NBC as
they love a sensational story where someone gets injured.
Shaun Rimmer
spademan o---[) * <steve.e...@its.lancscc.gov.uk> wrote in message
news:3f546349$1...@news.yourcomms.net...
>
> "Shaun Rimmer" <sh...@newtronic.co.uk> wrote in message
> news:bj1nhr$dq3nv$1...@ID-170198.news.uni-berlin.de...
> >
> > Doug Taylor <tayl...@choiceonemail.com> wrote in message
> > news:7107lv83bggi8ed3l...@4ax.com...
>
> > > So, my question is: has anybody who actually rides mountain bike with
> > > any frequency (such as the amb crowd) experienced this phenomenon or
> > > heard of anybody loosing a wheel? If so, any serious injuries? Is
> > > the sky really falling or can we get back on our bikes and ride?
> >
> > Well, I got a Hope Mini on the front, with the big rotor,
>
> Strangely smaller rotors are thought to be worse as the angle of braking
> force is aligned more closely with the dropout angle.
Right - gotcha.
> > bike is heavy and
> > so is my pack.
>
> But you're a skinny lad like me so it evens out. I don't think this is a
> factor though.
Aye, I am a skinny lad, but when you factor in a 36lb bike and a pack that
can be getting on for 10lb's, it makes a difference. Total weight being
stopped has surely gotta factor into the braking forces?
> > Big bad grippy knobbies, and I don't half hammer on that
> > brake lever some times when coming to a stop - _never_ had a problem,
not
> > slight, not at all, never. I do get _very_ medieval on my QR skewers
> though
> > (closed 'em with my feet before now......), enough that I'm worried for
> the
> > life of my dropouts, heheheheh..........
>
> Seems like the most sensible thing to do for now.
I really don't see how, with my set-up, I'm gonna have any trouble (even
though I understand the physics behind the 'problem' more than well enough).
> > This is my own experience only, obverously.
> >
> > Shaun aRe
> >
>
> Steve.
Cheers Steve,
Shaun aRe
Super Slinky
> The fact that trolls like yourself lie about me on usenet certainly
> doesn't faze me in the least. I'm not stupid and I realised right from
> the start that with so many powerful vested interests involved I was
> going to end up the scapegoat anyway, it's tough shit but that's what
> whistleblowers have always got for their trouble. I don't want it to
> be _my_ campaign but neither am I prepared to sit back and do nothing
> while the manufacturers stick their heads in the sand and riders
> continue to get seriously hurt by this design fault.
Troll? How so? Because I don't agree with you? Everything I said was the
perfect truth as I see it, and it was said in less offensive terms than
you just used. Who are the powerful entities standing against you? The
manufacturers? Which one? I doubt that the manufacturers are quivering
in their shoes just yet. Not only is there a lack of evidence of a
widespread problem, but it would be impossible to assign blame for any
particular accident. Nobody could ever be certain if a skewer was
installed correctly by the user and it is well known that many users
install them improperly. Have you ever decided which manufacturers are
to get the blame for this alleged problem? Is it the fork makers like
RockShox and Marzocchi, disc brake makers, or the bicycle integrators
like Trek and Specialized?
> Several of the journalists who have written about this (and who all
> agree that there is a real problem, having reviewed the ample evidence
> in its favour) are in fact trained engineers with long experience in
> the bicycle industry, and some of the most respected expert witnesses
> in bicycle liability litigation bar none (also trained engineers) have
> stated their clear opinion that there is a dangerous fault. Many
> people have now replicated the phenomenon by themselves, no special
> equipment required, and it is increasingly ridiculous that the
> manufacturers pretend they don't know about it. Some people who work
> in the industry, who know for sure there is a problem, have stated
> that they don't want bodies such as the CPSC involved precisely
> because they _do_ know there is a real problem, and it's going to cost
> someone quite a lot of money to fix.
Journalists? Spare me. Journalists are out to sell their magazine. No
wonder you piqued their interest, because such a controversy would
certainly be a windfall for them. Even if the story turns out to be a
dud, they can sell more rags by printing follow-up stories stating that
there didn't turn out to be much of a problem after all. Expert
witnesses for litigation? Again, money in the bank for them. You
certainly know how to choose your friends. I have not been able to
replicate the problem after beating the hell out of my bike all summer,
nor have I even heard a whisper of it from others, except from you. The
CPSC was evidently underwhelmed by your story and there are some recall
notices on their web site that are almost laughable, like the Bianchi
recall for bikes made in the early '80s where there have only been 3
reports of failures.
> Of course, the longer this drags on, the more it will cost when it
> eventually does get fixed. But you'd rather attack me than actually
> ask the manufacturers for some answers. That says plenty about your
> motivation and interest in this problem. Never mind, it will
> eventually be solved, but it will be despite your contribution rather
> than with the help of it. You may think you are saving the
> manufacturers from unnecessary interference, but you are actually
> encouraging them to dig their own graves. I hope you are proud of
> yourself.
I don't need any answers from the manufacturers, because I don't have
any questions for them. For one thing, I understand that biking is
inherently dangerous almost to the point of being a daredevil stunt, if
you ride aggressively. I have had a half dozen spills this summer, a few
of them quite painful and none of them involved mechanical failure. Most
times I will be blazing along thinking I am invincible and a moment
later I'm in a heap with the bike on top of me wondering what the hell
just happened. I can hit a rut or a small ledge at any time that can
send me over the bars in a crash indistinguishable from lousing a front
wheel. Far more common than losing the front wheel is breaking the frame
or bending a wheel, both of which can have similar consequences. Yet
they still sell lightweight, low spoke count rims and triple butted
lightweight aluminum frames and nobody is clamoring for them to stop.
Your own bias on this subject is self-evident. At no time have I seen
you admit that your accident was a very unusual case. A tandem bike, no
retention lips, very unusual dropout angle. Yet we are all supposed to
think that just because it happened to you in such freakish
circumstances that it must be happening everywhere. But I suppose if you
were to admit that, then you wouldn't have much to talk about, and the
new book 'Unsafe at Any Speed' by James Annan and Jobst Brandt wouldn't
sell any copies.
Pete Jones
Annan) blathered:
>> There is a theory, conjured by one person by the name of James Annan,
>> who rides a tandem mountain bike, and a few roadies who don't ride
>> mountain bikes at all, that repeated use of the disc brake loosens the
>> skewer, and when the skewer is loose enough, the brake ejects the wheel
>> out of the dropout.
>
>> The fact that almost nobody who
>> actually uses bikes so equipped believes him or takes his scare tactics
>> seriously doesn't faze him in the least.
>
>The fact that trolls like yourself lie about me on usenet certainly
>doesn't faze me in the least. I'm not stupid and I realised right from
>the start that with so many powerful vested interests involved I was
>going to end up the scapegoat anyway
Why do Mountain Bikers always LIE?
Eric Murray
Westie <Wes...@invalid.address.null> wrote:
>If you look at the brakes and the forces involved it's reasonably obvious
>that discs make a loose skewer more likely to pop out than other types of
>brakes. How much more likely? Who knows? That's the problem. All I know
>is that if I was braking and had a very loose QR then I would not want that
>front wheel to get ANY air under it. The moment that wheel has the
>opportunity to move downwards while the disc calipers are clamped on that
>rotor the torque will twist that wheel down and out!
> It's not a matter of
>it 'falling out' due to gravity. It'll be pushed out with force while under
>braking.
But the torque in that case is generated by the rotational
energy in the wheel and tire... and even with a heavy tire there
isn't much energy there.
I tried the experiment of loosening my front QR until it barely held
on to the (lawyer lips filed off) fork tabs, then spinning
the front tire and applying the brake. The wheel didn't jump
out of the fork. I also tried pushing the bike and applying
the front brake, and the wheel didn't jump out of the forks then
either.
Of course this is an exceedingly unscientific experiment. But
it did satisfy me that I'm in no danger of losing my front wheel
even with no lawyer lips, as long as I make sure my front qr is tight.
>Anyway, the initial problem is that the QR was loose in the first place and
>that's just asking for an accident to happen - discs or no discs. The disc
>brakes only exacerbate an existing fault, IMO. It'll be interesting to see
>how the issue develops and what, if any, changes are made to fork design.
Hopefully the changes ,if they occurr, won't inconveience all of us
in order to protect a few careless people from themselves.
Eric
mule
> energy in the wheel and tire... and even with a heavy tire there
> isn't much energy there.
I *think* you're wrong there.
The torque is generated by the braking force, which is a function of the
rider mass, deceleration and wheel/disc geometry.
> I tried the experiment of loosening my front QR until it barely held
> on to the (lawyer lips filed off) fork tabs, then spinning
> the front tire and applying the brake. The wheel didn't jump
> out of the fork. I also tried pushing the bike and applying
> the front brake, and the wheel didn't jump out of the forks then
> either.
You're only decelerating the wheel here...
--
...meandering mule...
Eric Murray
mule <meandering...@nospam.breathe.com> wrote:
>> But the torque in that case is generated by the rotational
>> energy in the wheel and tire... and even with a heavy tire there
>> isn't much energy there.
>
>I *think* you're wrong there.
>The torque is generated by the braking force, which is a function of the
>rider mass, deceleration and wheel/disc geometry.
How does rider mass affect it when the wheel's in the air?
Stephen Baker
>How does rider mass affect it when the wheel's in the air?
How does that affect he price of tea in China?
How many times do you apply your front brake when the wheel is not touching
ground (and expect to see something happen braking-wise)?
Steve always knew disc brakes were a bad idea.....
mule
>>> energy in the wheel and tire... and even with a heavy tire there
>>> isn't much energy there.
>>
>>I *think* you're wrong there.
>>The torque is generated by the braking force, which is a function of
the
>>rider mass, deceleration and wheel/disc geometry.
>
> How does rider mass affect it when the wheel's in the air?
Hi Eric,
My misunderstanding. Sorry! =oP
Under *those* conditions you're absolutely right.
Having said that, like you say your experiment is a little
"unscientific".
I wouldn't call it unscientific, more "un-realistic".
If/when the bike really IS in the air, both the bike and the tyre could
have other forces exerted on it - the fork and tyre may try to move in
different directions (either from subsequent user input or the previous
reaction from the ground) - so that would be difficult to reproduce in
your garage.
Even a slightly "off" landing might be enough to dislodge the wheel in
reality.
...still...like Westie says I wouldn't want air under my wheel if I could
see that my skewer was loose (and I wasn't in a position to fix it)...
=o]
--
...meandering mule...
James Annan
> >doesn't faze me in the least.
>
>
Hey, it wasn't in capital letters! It's only a handful of trolls doing
it, not everyone who rides a bike as MV might like to think. Plenty of
Mountain Bikers have seen the problem with their own eyes.
James
James Annan
> Journalists? Spare me. Journalists are out to sell their magazine. No
> wonder you piqued their interest, because such a controversy would
> certainly be a windfall for them. Even if the story turns out to be a
> dud, they can sell more rags by printing follow-up stories stating that
> there didn't turn out to be much of a problem after all. Expert
> witnesses for litigation? Again, money in the bank for them. You
> certainly know how to choose your friends.
Actually, I doubt that many of them would consider me a friend, but
fortunately this issue is not about friendship and it certainly isn't
about cliques of pals all telling each other that there isn't a
problem as you seem to be looking for here. It's about competence and
honesty, and these people are all competent to understand the problem
and honest enough to admit it, whatever they might think of me
personally.
> The
> CPSC was evidently underwhelmed by your story and there are some recall
> notices on their web site that are almost laughable, like the Bianchi
> recall for bikes made in the early '80s where there have only been 3
> reports of failures.
You wish to debate the nature of consumer protection law in the USA,
that's your right. I'm just telling you how it is, not how it should
be. If the fork manufacturers thought that this defect would be
considered acceptable by the courts then why do you think have they
always denied so vehemently that it exists? It would be much easier
for to just say `yeah dude, shit happens' than invest in forensic
analysis to `prove' the rider was at fault, using analysis that is now
seen to be faulty.
> I don't need any answers from the manufacturers, because I don't have
> any questions for them. For one thing, I understand that biking is
> inherently dangerous almost to the point of being a daredevil stunt, if
> you ride aggressively. I have had a half dozen spills this summer, a few
> of them quite painful and none of them involved mechanical failure. Most
> times I will be blazing along thinking I am invincible and a moment
> later I'm in a heap with the bike on top of me wondering what the hell
> just happened. I can hit a rut or a small ledge at any time that can
> send me over the bars in a crash indistinguishable from lousing a front
> wheel.
You impress me with your tales of daring-do, but you would not speak
so lightly of front wheel loss if you had experienced it. It is
generally substantially worse than simply going over the handlebars,
because your _first_ movement is directly downwards rather than up in
an arc, giving you much less time to react (the impact energy is the
same). It's also something that can happen without warning on a
completely tame bit of trail when you are descending at high speed.
> Your own bias on this subject is self-evident. At no time have I seen
> you admit that your accident was a very unusual case.
You haven't been looking. My accident was a very unusual case.
However I am sure that this will not prevent you from repeating the
question again later, under the pretence of innocence, in the hope
that you will trick others into believing that this problem is all in
my head. I have noticed that two incidents have been reported in this
thread, one of the skewer loosening and one of total wheel loss.
Nevertheless, you and Doug Taylor and your ilk will no doubt
conveniently forget these comments and return later with your lie that
it hasn't happened to any of the real bike riders in `the amb crowd'.
James
Doug Taylor
> Nevertheless, you and Doug Taylor and your ilk will no doubt
> conveniently forget these comments and return later with your lie that
> it hasn't happened to any of the real bike riders in `the amb crowd'.
Dude, accusing people who have legitimate questions, doubts, disagreements,
and/or differing opinions concerning your *hypothesis* of "lying" will only
serve to cast doubt on your credibility. We may be mistaken, wrong, or
misguided, be we are not lying.
Didn't the bard say: "The lady doth protest too much, methinks." -- Hamlet
(III, ii, 239)?
Also, get you usenet terminology correct. A "troll" is an analogy to the
sport of fishing: someone casts a deliberately provacative, disingenuous or
false post in the hope that some clueless newbie or dumbass will bite the
bait, i.e. take it seriously and react.
That is not the same thing as posting honest opinions, whether or not you
agree with them, think they have any merit, or even consider them at all.
Spider, Slinky and I may be acting as devils advocates, but we are not
trolling.
Thanks for your attention, wanker ;-)
Ian
> Alex Bird said...
>
> > Why would discs be more likely to release the wheel? This makes no
> > sense to me.
> >
> > Alex
>
> There is a theory, conjured by one person by the name of James Annan,
> who rides a tandem mountain bike, and a few roadies who don't ride
> mountain bikes at all, that repeated use of the disc brake loosens the
> skewer, and when the skewer is loose enough, the brake ejects the wheel
> out of the dropout.
Is it supposed to "unscrew" the skewer? If so, why would disc brakes be
susceptible and not v-brakes or cantis? The moment created by the latter two
would be larger I would think. Or do the disc brake calipers introduce a
side load that "uncams" the QR, or simply forces the wheel out of the
dropout? If that side load creates a moment that wants to rotate one end of
the skewer out of the dropout, things could get real ugly. Relocating the
brake caliper and/or changing the angle of the dropout should fix that
issue.
> There have been no documented cases of it ever
> having actually happened to anyone, except to maybe James Annan himself.
> Myself, Doug Taylor and Spider have been the main people taking the
> skeptical side of the debate over in rec.bicycles.tech. James Annan
> wants to attribute every wheel loss, and seemingly every off-road biking
> injury, to his pet theory. He is quite close-minded to any opposing
> viewpoint. I believe that it actually happened to him, but his was a
> very special case. He was on a tandem which can exert extreme forces in
> braking, much more than you would see on a single person bike. Worse,
> his fork was very poorly designed. It almost looked like it was built to
> have this failure. It had no retention lips and this feature alone would
> have almost certainly prevented the wheel from going anywhere. The fork
> also had a very odd dropout angle that slanted toward the rear and ran
> parallel with the brake rotor. Vertical dropouts would have resisted
> some of the ejection force.
::struggling to visualize the geometry::
If you could draw a line, at the angle of the dropout, through the axis of
rotation (in the plane of rotation), would that line intersect the brake
caliper at any point? I would think the preferred layout would have this
line normal to one drawn from the center of the brake caliper through the
axis of rotation. That way any moment created by a side load would not tend
to force one end of the skewer out of the dropout.
Then again, it's been more than ten years sinces any classes that dealt with
this sort of thing, so I could simply be full of it.....
-Ian
P.S. Or might there be a twisting load on the hub that tends to slowly
"walk" the wheel out of the dropouts? I'd better stop, or someone's going to
ask me to do the math, and show my work... One last thing: Has this ever
been a problem with motorcycles? If so, how was it dealt with there?
>
> Now he is badgering bicycle manufacturers, journalists and the American
> Consumer Product Safety Commission, not to mention us on the Internet,
> that something must be done about it. The fact that almost nobody who
> actually uses bikes so equipped believes him or takes his scare tactics
> seriously doesn't faze him in the least. My opinion is that retention
> lips make this failure almost impossible. This opinion is backed up by
> the fact that nobody can find any cases of it happening to anyone but
> him. His bike didn't have them, the vast majority of bike sold in the US
> do and have for years. Europe may be different.
spademan o---[) *
"Ian" <ibu...@NOSPAMaol.com> wrote in message
news:9wh5b.575$f63.33...@newssvr13.news.prodigy.com...
>
> "Super Slinky" <sli...@newmail.net> wrote in message
> news:MPG.19bdc03c9...@netnews.comcast.net...
... One last thing: Has this ever
> been a problem with motorcycles? If so, how was it dealt with there?
I think they stopped using Q.R. skewers on motorcycles a while ago......
spademan o---[) *
"Ian" <ibu...@NOSPAMaol.com> wrote in message
news:9wh5b.575$f63.33...@newssvr13.news.prodigy.com...
>
> news:MPG.19bdc03c9...@netnews.comcast.net...
> > Alex Bird said...
> >
> > > Why would discs be more likely to release the wheel? This makes no
> > > sense to me.
> > >
> > > Alex
> >
> > There is a theory, conjured by one person by the name of James Annan,
> > who rides a tandem mountain bike, and a few roadies who don't ride
> > mountain bikes at all, that repeated use of the disc brake loosens the
> > skewer, and when the skewer is loose enough, the brake ejects the wheel
> > out of the dropout.
>
> Is it supposed to "unscrew" the skewer? If so, why would disc brakes be
> susceptible and not v-brakes or cantis?
As I understand it discs vibrate more than V's, and are located closer to
the dropout. Its this localised vibration that may be causing the Q.R. nut
to unscrew gradually.
> P.S. Or might there be a twisting load on the hub that tends to slowly
> "walk" the wheel out of the dropouts?
That has also been suggested. The braking forces from a disc are on one side
of the forks only and so this may force the legs to twist, causing an
inchworming effect of loosening the nut. Anyone remember the dual disc
set-up that was promoted 3 or 4 years ago?
Cheers,
Steve.
Westie
"Stephen Baker" <saild...@aol.comnospam> wrote in message
news:20030902164614...@mb-m18.aol.com...
> Eric Murray says:
>
> >How does rider mass affect it when the wheel's in the air?
>
> How does that affect he price of tea in China?
> How many times do you apply your front brake when the wheel is not
touching
> ground (and expect to see something happen braking-wise)?
Haven't you heard of airbrakes? ;-)
Saying 'air' under the tyre was perhaps over-simplifying it. I meant any
time the wheel isn't firmly pressed against the ground.
There are plenty of times I find myself braking on ruts and waterbars, rocks
and humps and bumps. Anytime the wheel rolls or drops off the back end of
one of those while you are braking there is potentially a brief moment when
the 'upwards' force of the ground against the wheel is less than the
'downwards' force of the skewer trying to get out of the fork. Theoretically
(I love that word because it allows so many possibilities) I can see the
torque from the hard braking twisting that wheel out of the dropouts.
None of it is really 'in the air' .
More of a case of a situation where one normally weaker force momentarily
overcomes another normally larger force.
--
Westie
-not an engineer.-
Stephen Baker
>Haven't you heard of airbrakes? ;-)
Ppppffftttt!!!! I seem to remember them making noises like that ;-))
>Anytime the wheel rolls or drops off the back end of
>one of those while you are braking there is potentially a brief moment when
>the 'upwards' force of the ground against the wheel is less than the
>'downwards' force of the skewer trying to get out of the fork.
It seems to me that the moment the wheel leaves the ground, there should be
less force acting on it, because it can only be affected by its own weight (not
plus the bike and rider). Unless it speeds up remarkably at this point, the
forces will be lower, although maybe more aligned to wheel ejection.
Just my 0.02 as an engineer, even if not a bike engineer..
>Theoretically
>(I love that word because it allows so many possibilities)
Hehe!
Steve
spademan o---[) *
"Westie" <Wes...@invalid.address.null> wrote in message
news:bj4lpj$ifk$1...@lust.ihug.co.nz...
>
> "Stephen Baker" <saild...@aol.comnospam> wrote in message
> news:20030902164614...@mb-m18.aol.com...
> Saying 'air' under the tyre was perhaps over-simplifying it. I meant any
> time the wheel isn't firmly pressed against the ground.
> There are plenty of times I find myself braking on ruts and waterbars,
rocks
> and humps and bumps. Anytime the wheel rolls or drops off the back end of
> one of those while you are braking there is potentially a brief moment
when
> the 'upwards' force of the ground against the wheel is less than the
> 'downwards' force of the skewer trying to get out of the fork.
Theoretically
> (I love that word because it allows so many possibilities) I can see the
> torque from the hard braking twisting that wheel out of the dropouts.
> None of it is really 'in the air' .
> More of a case of a situation where one normally weaker force momentarily
> overcomes another normally larger force.
> --
> Westie
> -not an engineer.-
Take your Q.R. skewer out, ride along and grab a handful of front brake
(assuming you have disc brakes). Aha, it is not necessary for the wheel to
leave the ground for the forces to wrench the wheel you muse from your
hospital bed...
Steve.
Super Slinky
> Actually, I doubt that many of them would consider me a friend, but
> fortunately this issue is not about friendship and it certainly isn't
> about cliques of pals all telling each other that there isn't a
> problem as you seem to be looking for here. It's about competence and
> honesty, and these people are all competent to understand the problem
> and honest enough to admit it, whatever they might think of me
> personally.
But a clique of pals saying that there is a problem is OK. Gotcha. A few
stories of loose skewers doesn't prove a thing. I have had loose QRs in
the past, mostly on bikes with rim brakes. If I think back, I can
usually remember recently removing the wheel and most likely forgetting
to do the QR properly. It is then when you realize what the retention
lips are for and you don't cuss as much the next time you have to loosen
the skewer those extra turns to get the wheel off. Just because you
talked a few people into seeing the world through your filtered
perceptions also means nothing. Linus Pauling once said that taking
vitamin C would prevent the common cold and gave scientific reasons for
it. It turns out to be bunk, but now we are stuck with that junk science
urban myth and millions still swear by it.
I'm sorry James, but I have read most of the 'evidence' you cite, and as
a trained scientist I can only conclude that your ideas on this subject
are an elaborate pipe dream. If skewers were unscrewing just by applying
a disc brake we would see more evidence of it. For one thing we would be
grinding our dropouts to dust in short order, whether or not we ever
noticed a loose QR or ever lost a wheel. There is very little room for
the up and down motion of the skewer that you claim inside the retention
lips and a lot of unscrewing must happen. At some point the rider would
sense an obnoxious knocking coming from the front fork well before the
skewer was loose enough to get past the retention lips. There would also
be other telltale signs like brake rub, a loose feeling in the fork, and
god knows what else. Most riders are very sensitive to these types of
mechanical warning signs.
> You wish to debate the nature of consumer protection law in the USA,
> that's your right. I'm just telling you how it is, not how it should
> be. If the fork manufacturers thought that this defect would be
> considered acceptable by the courts then why do you think have they
> always denied so vehemently that it exists? It would be much easier
> for to just say `yeah dude, shit happens' than invest in forensic
> analysis to `prove' the rider was at fault, using analysis that is now
> seen to be faulty.
Maybe they deny it because the have done the engineering and the testing
and none of it has revealed the problems you claim to be so universal. I
work in a testing lab and we get all sorts of ridiculous claims from
customers all the time. We are the experts in our field of work and we
know the difference between an intelligent question and someone who
doesn't know what they are talking about.
> You impress me with your tales of daring-do, but you would not speak
> so lightly of front wheel loss if you had experienced it. It is
> generally substantially worse than simply going over the handlebars,
> because your _first_ movement is directly downwards rather than up in
> an arc, giving you much less time to react (the impact energy is the
> same). It's also something that can happen without warning on a
> completely tame bit of trail when you are descending at high speed.
The only time I ever lost a front wheel in 30 years of biking was when I
was about 14 trying to ride a wheelie on a bike where I hadn't tightened
the axle. As for your particular wheel loss scenario, I doubt that the
rider would completely lose the wheel. The ejection force occurs on the
brake side only. Moreover, the skewer would have to be loose enough to
get around both retention lips. No, what would happen most often is that
the disc side would eject while the opposite side stayed in the dropout
and you would get a standard endo much like locking the brake or bending
the rim.
> You haven't been looking. My accident was a very unusual case.
Yet it is still the original reason for all this hoopla and the only
known case of disc brakes causing a wheel ejection. And there is more
silliness that I didn't include in other posts. It is obvious that your
QR did not unscrew at all, but the wheel was forcibly ripped from the
dropouts by brute force made possible by the fact that your fork didn't
have retention lips and your skewer didn't have knurled contact faces.
> However I am sure that this will not prevent you from repeating the
> question again later, under the pretence of innocence, in the hope
> that you will trick others into believing that this problem is all in
> my head. I have noticed that two incidents have been reported in this
> thread, one of the skewer loosening and one of total wheel loss.
> Nevertheless, you and Doug Taylor and your ilk will no doubt
> conveniently forget these comments and return later with your lie that
> it hasn't happened to any of the real bike riders in `the amb crowd'.
I'll keep commenting on it until I get tired of it. After that, if you
decide to pursue this nonsense, you can get shown as the fraud that you
are by those who have more experience in the subject than either of us.
I strongly doubt that the manufacturers are as defenseless as you think
they are. Were not talking about a one in a million freak accident like
a car catching fire or an SUV tire blowing out. Millions of bikes have
used disc brakes for years and after all that time it takes James Annan
to tell us that we are all in mortal peril. You really need to get over
yourself.
Colin Swan
>Is it supposed to "unscrew" the skewer? If so, why would disc brakes be
>susceptible and not v-brakes or cantis? The moment created by the latter two
>would be larger I would think. Or do the disc brake calipers introduce a
>side load that "uncams" the QR, or simply forces the wheel out of the
>dropout? If that side load creates a moment that wants to rotate one end of
>the skewer out of the dropout, things could get real ugly. Relocating the
>brake caliper and/or changing the angle of the dropout should fix that
>issue.
I think the theory is that the locked (or heavily braked) wheel will
tend to rotate backwards (due to the friction force from the ground)
with the brkae blocks or pads as the pivot point. With a rim brake,
the pivot is at the top of the forks, so the possible arc of the axle
is stopped effectively by the dropout. A disk, however, has a caliper
that is behind and slightly above the axle line, so in the same case
as above, the arc that the axle would want to follow is down and back,
which could in theory force the axle out of the dropouts.
I can see the physics, but I don't think that this is a big problem,
as it relies on the wheel being on the ground to happen. If you are
braking that hard, then weight will be transferred to the front wheel,
and that weight, pivoting around the rear axle has a greater
mechanical advantage than the force pivoting around the brake pads. If
the wheel is airborne, then there is no force.
Also, the manufacturers have already introduced the tabs
(lawyer-lips?) to stop wheels just falling out if your QR is undone,
which will also help to stop this happening. If anyone doesn't have
these, or has filed them off, then they had better check their QR a
lot!
I have disks, and this doesn't top my list of worries.
Colin
John Morgan
side
> of the forks only and so this may force the legs to twist, causing an
> inchworming effect of loosening the nut.
>
Yet another reason to own a Cannondale with a Lefty. <g>
-John Morgan
Ian
Oh, a wiseguy huh? Why I oughta....
Depending on what's happening, it may make no difference if there is a QR or
not. I would think motocross bikes would suffer from similar issues; perhaps
even worse, since the loads would be higher. If they have a more positive
form of wheel retention it may be beneficial for mountain bike manufacturers
to adopt something similar.
-Ian
Ian
news:3d2clv8u5rdor41gs...@4ax.com...
> On Wed, 03 Sep 2003 08:21:25 GMT, "Ian" <ibu...@NOSPAMaol.com> wrote:
>
> >Is it supposed to "unscrew" the skewer? If so, why would disc brakes be
> >susceptible and not v-brakes or cantis? The moment created by the latter
two
> >would be larger I would think. Or do the disc brake calipers introduce a
> >side load that "uncams" the QR, or simply forces the wheel out of the
> >dropout? If that side load creates a moment that wants to rotate one end
of
> >the skewer out of the dropout, things could get real ugly. Relocating the
> >brake caliper and/or changing the angle of the dropout should fix that
> >issue.
>
> I think the theory is that the locked (or heavily braked) wheel will
> tend to rotate backwards (due to the friction force from the ground)
> with the brkae blocks or pads as the pivot point. With a rim brake,
> the pivot is at the top of the forks, so the possible arc of the axle
> is stopped effectively by the dropout. A disk, however, has a caliper
> that is behind and slightly above the axle line, so in the same case
> as above, the arc that the axle would want to follow is down and back,
> which could in theory force the axle out of the dropouts.
>
Ah, the brake caliper as the pivot point. That works. A simple experiment
shows that this does occur, at least on my bike, but the skewer has to be
really, really loose to get past the tabs.
> I can see the physics, but I don't think that this is a big problem,
> as it relies on the wheel being on the ground to happen. If you are
> braking that hard, then weight will be transferred to the front wheel,
> and that weight, pivoting around the rear axle has a greater
> mechanical advantage than the force pivoting around the brake pads. If
> the wheel is airborne, then there is no force.
>
So, in a practical braking situation, the forward weight transfer should be
sufficient to counteract the force trying to rotate the wheel out of the
dropouts.
This should be fairly easy to test experimentally. Have the proponents of
this idea made an effort to do so?
> Also, the manufacturers have already introduced the tabs
> (lawyer-lips?) to stop wheels just falling out if your QR is undone,
> which will also help to stop this happening. If anyone doesn't have
> these, or has filed them off, then they had better check their QR a
> lot!
>
> I have disks, and this doesn't top my list of worries.
>
This is the first I've ever heard of it.
-Ian
> Colin
James Annan
> There is very little room for
> the up and down motion of the skewer that you claim inside the retention
> lips
Nevertheless, it moves, and has been directly measured by several
cyclists and scientists, including the Velotech testing lab in
Germany. Oh, of course they must be biased too, because they are
German, or something.
> and a lot of unscrewing must happen. At some point the rider would
> sense an obnoxious knocking coming from the front fork well before the
> skewer was loose enough to get past the retention lips. There would also
> be other telltale signs like brake rub, a loose feeling in the fork, and
> god knows what else. Most riders are very sensitive to these types of
> mechanical warning signs.
This is an argument that wheel loss cannot occur for either reason,
unscrewing or incorrect installation, since the rider will always
notice the problem and stop. Well, it's as valid an argument as any
other you have put forward. The existence of cyclists who have lost
their front wheel puts a small stick in your spokes here.
> Maybe they deny it because the have done the engineering and the testing
> and none of it has revealed the problems you claim to be so universal. I
> work in a testing lab and we get all sorts of ridiculous claims from
> customers all the time. We are the experts in our field of work and we
> know the difference between an intelligent question and someone who
> doesn't know what they are talking about.
Just out of interest, did you read Pace's Open Letter? Did you see the
simple errors contained in it? Do you still think they are the
experts?
It's abundantly clear that this failure method was simply not
considered at all by the manufacturers. If they had seen it, they
would have designed it out at no cost or inconvenience. Whether this
initial error amounts to gross negligence is not for me to judge, but
continuing indefinitely with the design now that the error has been
explained will certainly not be considered acceptable.
> As for your particular wheel loss scenario, I doubt that the
> rider would completely lose the wheel. The ejection force occurs on the
> brake side only. Moreover, the skewer would have to be loose enough to
> get around both retention lips. No, what would happen most often is that
> the disc side would eject while the opposite side stayed in the dropout
> and you would get a standard endo much like locking the brake or bending
> the rim.
More pointless hypothesising based on no understanding of the system.
What do you think will hold the wheel in on the RHS, once the LHS is
free?
> Yet it is still the original reason for all this hoopla and the only
> known case of disc brakes causing a wheel ejection.
What do you mean by 'known'? How is it any better documented than any
of the other descriptions of failure? All I did was take a few
pictures of the aftermath and put them on a web site, it's no
different from the other anectodal evidence you dismiss. You can say
it's never yet been proved to happen in a court of law, but there are
a large number of anecdotal cases, and mine is not separable from the
rest.
It's interesting to note that following my crash, many people
initially tried to make up all sorts of implausible explanations as to
how the failure could have occurred _other_ than the obvious direct
pull out. Many people have a complete mental block about the
possibility of correctly used QRs failing to retain a wheel, and
although all these original sceptics came round over time, it seems
unlikely that your ego will allow you to back down now that you have
dug yourself such a big hole. You will continue to bluster about how
you are a 'trained scientist' and don't believe it, long after the
whole issue has been put to bed. A decent scientist would look at the
evidence and change their mind.
> After that, if you
> decide to pursue this nonsense, you can get shown as the fraud that you
> are by those who have more experience in the subject than either of us.
The independent evidence is all piling up one one side of the argument
so far. Every aspect of the failure has been replicated in detail
under repeatable conditions.
James
Super Slinky
> Nevertheless, it moves, and has been directly measured by several
> cyclists and scientists, including the Velotech testing lab in
> Germany. Oh, of course they must be biased too, because they are
> German, or something.
Mine doesn't move at all. My Fox fork is about 3 months old and I have
put a lot of miles on it on and off road. I have had brake endos at
least twice, several other spills, and on one fast roller coaster trail
I broke the frame on the bike it was installed on. Through all that, the
skewer has not moved in the dropouts, not even once, not even a little
bit. The paint in the dropout is as pristine as the day I bought it.
Evidently I know something that your ace testers don't, and I have never
gone to extra trouble to get my skewers super tight. The testing you
cite means nothing without knowing their methods. I tried to follow the
links to the Velotech testing but I needed a password to see it. I know
that not everyone was impressed with the testing in the Singletrack
World forum.
> This is an argument that wheel loss cannot occur for either reason,
> unscrewing or incorrect installation, since the rider will always
> notice the problem and stop. Well, it's as valid an argument as any
> other you have put forward. The existence of cyclists who have lost
> their front wheel puts a small stick in your spokes here.
Well, it is a rare thing to lose a wheel compared to the usual failures.
And wheel loss can be caused by other things than loose skewers, like a
broken skewer or a broken dropout. Think about the guy that does up his
skewer stupidly tight. At some point you can tighten the skewer too much
and it will break. If you were at that threshold and started your ride,
maybe the extra forces that are exerted by aggressive riding can send it
over the edge. The dropouts may break more than is commonly thought,
because it would be impossible to know after the fact looking at a
trashed fork if the breakage caused the crash or the crash caused the
breakage. Either of these scenarios seem like more likely explanations
for Russ Pinder's accident than your theory.
> Just out of interest, did you read Pace's Open Letter? Did you see the
> simple errors contained in it? Do you still think they are the
> experts?
I read it, but I don't remember the details. I just did a quick search
and couldn't find it again. To be honest, Pace forks do not impress me.
I have seen photos of recent vintage ones that didn't have retention
lips. Even my '99 Taiwanese GT rigid steel forks have retention lips. I
think it is a sensible feature, annoying as they may be at times. Other
than that, Pace is a minor player in the world of forks, at least on
this side of the pond. A spokesman from Marzocchi would have made for a
more interesting read to me.
> It's abundantly clear that this failure method was simply not
> considered at all by the manufacturers. If they had seen it, they
> would have designed it out at no cost or inconvenience. Whether this
> initial error amounts to gross negligence is not for me to judge, but
> continuing indefinitely with the design now that the error has been
> explained will certainly not be considered acceptable.
I agree that what we have is a grandfathered and bastardized design and
could definitely use some refinement. But in spite of that, the
experience of millions of users has shown that it is as safe as most
other parts of the bike. After all, QRs and dropouts are not safety
features, they are convenience features. The bike would be safer without
them, discs or no discs. The extensive use of aluminum is another safety
compromise. At some point in time, if you keep them long enough, your
alloy handlebars will break. But the cycling world, and that includes
you, has seen fit to trade safety for performance in many instances if
the danger isn't too great. That is why I see your tenacity in this
matter as misplaced. If you really wanted to improve bike safety, there
are bigger fish to fry than having a laser-like focus on this.
> More pointless hypothesising based on no understanding of the system.
> What do you think will hold the wheel in on the RHS, once the LHS is
> free?
The skewer should hold it long enough for the rider to do a standard
endo instead of planting the fork into the ground. Unless you are
assuming that the skewer just falls off, as it is ejected from the brake
side, it should bind up in the other side. Once the brake side is
ejected, it will change directions from down and out of the dropout to
more or less straight toward the rear of the bike. It is the brake side
that is pushed out, the other side should stay in the dropout,
especially since that side of the skewer is almost certainly going to
stay within the retention lips as the skewer moves to the left enough to
clear the retention lips on the brake side. If the skewer were to fall
apart, then it would be a different story. There is the danger of the
right side dropout breaking off due to twisting forces, but there is no
way of predicting the likelihood of that. Finally, the wheel will be
rubbing on the fork leg once the axle begins to be pushed out the brake
side. This extra friction alone will probably be enough to cause an endo
or lock the wheel. Note that I'm not just engaging in idle conjecture or
playing with force diagrams. I have done the experiment of loosening the
skewer, grabbing the brake and pushing the bike. The brake side is
pushed out, the right side stays put and the tire slams against the
fork. Under riding conditions the system would almost certainly bind up
with the wheel still attached. The wheel isn't just going to slide out
of there neatly and disappear.
> What do you mean by 'known'? How is it any better documented than any
> of the other descriptions of failure? All I did was take a few
> pictures of the aftermath and put them on a web site, it's no
> different from the other anectodal evidence you dismiss. You can say
> it's never yet been proved to happen in a court of law, but there are
> a large number of anecdotal cases, and mine is not separable from the
> rest.
As far as I know, it is the only documented failure. You did a thorough
job of documenting what happened to you. I have seen no other similar
cases which give clear evidence of what happened. A picture is worth a
thousand words. I would have been interested to see photos of Missy
Giove's dropouts or Russ Pinder's forks and wheel.
> It's interesting to note that following my crash, many people
> initially tried to make up all sorts of implausible explanations as to
> how the failure could have occurred _other_ than the obvious direct
> pull out.
I don't remember what I originally said about your crash. I now believe
it was caused by the brake pushing the wheel out of the dropouts. But
your case is unique in that the tandem bike would cause huge forces to
be exerted, you didn't have retention lips, your fork had unusual
dropout angles, your skewer had no knurling etc, etc. The unscrewing
mechanism that you keep trumpeting did not happen in your case. That is
obvious from the photos. That is something that you and Jobst Brandt
dreamed up so that you could extend what happened to you to everyone who
uses disc brakes, because what happened to you can't happen in the same
way to a fork equipped with retention lips. And that is where you and I
part company. You started out with a good point that most people didn't
know--that disc brakes cause an ejection force on the wheel--then
embellished it with that other junk because you saw a chance to make a
name for yourself by running around telling everyone the sky is falling.
> it seems unlikely that your ego will allow you to back down now that you
> have dug yourself such a big hole.
If you only knew how funny that sounds coming from you. Look up
projection in the dictionary and then tape what you typed above to your
monitor.
> The independent evidence is all piling up one one side of the argument
> so far. Every aspect of the failure has been replicated in detail
> under repeatable conditions.
>
> James
I don't think I have to tell you what I think is piling up.
bomba
> Depending on what's happening, it may make no difference if there is a QR or
> not. I would think motocross bikes would suffer from similar issues; perhaps
> even worse, since the loads would be higher.
Next time you walk past a motorcycle (doesn't have to be MX), have a
look at the axle setup. Then work out why this isn't a problem.
> If they have a more positive
> form of wheel retention it may be beneficial for mountain bike manufacturers
> to adopt something similar.
And welcome to the point...
Looks like manufacturers may well be changing the system for '05 models.
--
a.m-b FAQ: http://www.t-online.de/~jharris/ambfaq.htm
a.bmx FAQ: http://www.t-online.de/~jharris/bmx_faq.htm
spademan o---[) *
"Ian" <ibu...@NOSPAMaol.com> wrote in message
Is this where I look smugly at the 20mm thru-axle on my xc bike?
Steve.
Shaun Rimmer
Ian <ibu...@NOSPAMaol.com> wrote in message
'Cos MX bikes (and others) have big fat MoFo through axels, with a beefy
pinch bolt at the bottom of each fork leg to lock 'em up solid. Those things
are going _no where_ once bolted.
Shaun aRe
Shaun Rimmer
>
> "Ian" <ibu...@NOSPAMaol.com> wrote in message
> news:ueq5b.9128$WR5....@newssvr27.news.prodigy.com...
> > not. I would think motocross bikes would suffer from similar issues;
> perhaps
> > even worse, since the loads would be higher. If they have a more
positive
> > form of wheel retention it may be beneficial for mountain bike
> manufacturers
> > to adopt something similar.
> > -Ian
> >
>
> Is this where I look smugly at the 20mm thru-axle on my xc bike?
>
> Steve.
Gee, that's a bit of overkill Spadey.
Shaun aRe
Ian
"bomba" <myar...@hotmail.com> wrote in message
news:3F56E2E2...@hotmail.com...
> Ian wrote:
>
> > Depending on what's happening, it may make no difference if there is a
QR or
> > not. I would think motocross bikes would suffer from similar issues;
perhaps
> > even worse, since the loads would be higher.
>
> Next time you walk past a motorcycle (doesn't have to be MX), have a
> look at the axle setup. Then work out why this isn't a problem.
I'm unfamiliar with motorcycles, that's why I asked.
>
> > If they have a more positive
> > form of wheel retention it may be beneficial for mountain bike
manufacturers
> > to adopt something similar.
>
> And welcome to the point...
>
> Looks like manufacturers may well be changing the system for '05 models.
>
Could be about time, by the looks of things.
-Ian
Spider
> Super Slinky <sli...@newmail.net> wrote in message news:<MPG.19bfbf038...@netnews.comcast.net>...
>
> > There is very little room for
> > the up and down motion of the skewer that you claim inside the retention
> > lips
>
> Nevertheless, it moves, and has been directly measured by several
> cyclists and scientists, including the Velotech testing lab in
> Germany.
The "several cyclists" aren't scientists, and the initial conditions
are not controlled and not known.
The Velotech lab reported movement, but DID NOT report unscrewing.
> It's abundantly clear that this failure method was simply not
> considered at all by the manufacturers. If they had seen it, they
> would have designed it out at no cost or inconvenience. Whether this
> initial error amounts to gross negligence is not for me to judge, but
> continuing indefinitely with the design now that the error has been
> explained will certainly not be considered acceptable.
By you. If indeed the QR retention method is judged to be adequate by
the German lab, I suppose all that will be left for you is to raise
money for your planned class-action lawsuit.
> > As for your particular wheel loss scenario, I doubt that the
> > rider would completely lose the wheel. The ejection force occurs on the
> > brake side only. Moreover, the skewer would have to be loose enough to
> > get around both retention lips. No, what would happen most often is that
> > the disc side would eject while the opposite side stayed in the dropout
> > and you would get a standard endo much like locking the brake or bending
> > the rim.
>
> More pointless hypothesising based on no understanding of the system.
Actually, this is another area that depends on the equipment being
used. The QR still has to stretch a bit for this to occur as yo
hypothesize.
> What do you think will hold the wheel in on the RHS, once the LHS is
> free?
The tire hitting the fork. Endo.
> > Yet it is still the original reason for all this hoopla and the only
> > known case of disc brakes causing a wheel ejection.
>
> What do you mean by 'known'? How is it any better documented than any
> of the other descriptions of failure? All I did was take a few
> pictures of the aftermath and put them on a web site, it's no
> different from the other anectodal evidence you dismiss. You can say
> it's never yet been proved to happen in a court of law, but there are
> a large number of anecdotal cases, and mine is not separable from the
> rest.
Yes. ANd all the anecdotal cases add up to precisely nothing. If the
initial conditions are not known, then the outcome cannot be directly
attributed to some one cause. For reference, have you ever "just
known" that you locked the door to your house or car, then came back
to find them not locked? Or "just known" that you set your coffe mug
down next to the toaster, then found it in the bathroom? Or just
known that you did up your QR properly before you set out...
> It's interesting to note that following my crash, many people
> initially tried to make up all sorts of implausible explanations as to
> how the failure could have occurred _other_ than the obvious direct
> pull out.
Interesting why? Interesting that you had to explain it rationally to
people? Damn, sounds like science...
> Many people have a complete mental block about the
> possibility of correctly used QRs failing to retain a wheel, and
> although all these original sceptics came round over time, it seems
> unlikely that your ego will allow you to back down now that you have
> dug yourself such a big hole.
Or maybe your antagonistic style causes people to question EVERY
precept you lay down?
> You will continue to bluster about how
> you are a 'trained scientist' and don't believe it, long after the
> whole issue has been put to bed.
The "whole issue" has not been put to bed, and in fact, the unscrewing
mechanism is still in testing. And then there's the idea that at some
point, the unscrewing might stop, but the axle might still move, but
NOT out of the retention lips.
> A decent scientist would look at the
> evidence and change their mind.
I don't see evidence. I see a hypothesis, and an unscientific sample
of anecdotes.
> > After that, if you
> > decide to pursue this nonsense, you can get shown as the fraud that you
> > are by those who have more experience in the subject than either of us.
>
> The independent evidence is all piling up one one side of the argument
> so far.
Except that the only verifiable evidence is the very short blurb in
STW about the axle moving in the drop out. I'd be a little slower to
claim victory if I were you.
> Every aspect of the failure has been replicated in detail
> under repeatable conditions.
LOL. An outright lie.
SPider
James Annan
> Either of these scenarios seem like more likely explanations
> for Russ Pinder's accident than your theory.
Not to anyone who has read the descriptions that are already in the
public domain.
> > Just out of interest, did you read Pace's Open Letter? Did you see the
> > simple errors contained in it? Do you still think they are the
> > experts?
>
> I read it, but I don't remember the details. I just did a quick search
> and couldn't find it again.
You could try my web pages. Don't go to any trouble though, it might
put a dent in your confidence in the 'experts' who build the stuff you
ride.
> That is why I see your tenacity in this
> matter as misplaced. If you really wanted to improve bike safety, there
> are bigger fish to fry than having a laser-like focus on this.
Perhaps that is true, and it is really only this point that prompted
me to reply again. The rest of the nonsense can be left floating as a
testament to your determined stupidity.
There are always bigger fish to fry. If I could have the last 6 months
back, and use them to find a cure for cancer or solve the problem of
world poverty, then I certainly would take those over my relatively
minor discovery. But that's not the way things work. I worked on this
problem because it had affected me directly, and it certainly seemed
important enough to me to be worth dealing with. In contrast to the
bigger fish above, it didn't seem like anyone else was doing anything.
It also seemed to be somewhere where I might be able to make a useful
contribution, although someone with a mechanical engineering
background might well have got there a few days faster had they set
their mind to the task.
Having solved the problem, and had it checked out by several
experienced mechanical engineers, I told the manufacturers about it.
If they had taken me seriously back then, this would have been over
long ago, and they would presumably have been able to at least correct
the fault for 2004. But of course they were rude and dismissive, and
stuck their heads in the sand. They have a fixed mindset of always
blaming the user, and could not consider any alternative. It was their
arrogant ignorance that really got me motivated to make sure that this
problem was addressed. Meanwhile, more stories of serious injury keep
on turning up. I suppose I could just shrug my shoulders and say 'yeah
dude, shit happens', but I'd rather put a stop to it happening, and
I'm sad to see that you object to that. I can also see that the
manufacturers are busy digging themselves a hole, and that the longer
they delay, the more it will cost them. I don't give a shit any more
about the handful of incompetent engineers and executives responsible
for this mess, but there must be plenty of decent people working there
too. I also realise that I will get blamed by many for all
consequences regardless of the facts, so for that reason too it's in
my direct interest to get it fixed ASAP.
Some people think it's all ok because the manufacturers have said (off
the record) that they will fix the problem in 2005. Forget legal or
ethical, I just don't think that is possible, but perhaps I will be
proved wrong.
James
PS Oh, happy to hear about your fork. It reminds me of someone else
who rode a Fox fork hard for several months, with no problems. This
person also told me (last December) that they didn't believe disk
brakes could cause this problem. At the time, this attitude was
completely reasonable and widely shared as no-one had explained the
phenomenon, and the circumstantial evidence of a problem was rather
weak (although IMO enough to be worrying). That's not true any longer.
James Annan
> still_th...@hotmail.com (James Annan) wrote in message news:<c96ea403.0309...@posting.google.com>...
> > Nevertheless, it moves, and has been directly measured by several
> > cyclists and scientists, including the Velotech testing lab in
> > Germany.
>
> The "several cyclists" aren't scientists,
Some are scientists, some are cyclists, some are both and quite
possibly some are neither.
> and the initial conditions
> are not controlled
False
> and not known.
to you.
> If indeed the QR retention method is judged to be adequate by
> the German lab, I suppose all that will be left for you is to raise
> money for your planned class-action lawsuit.
I'm not planning any lawsuit, I have an apology from the builder of my
fork and I am confident he will not make the mistake again. I have no
paticular desire to cripple small businesses but I do want the problem
solved.
> Or maybe your antagonistic style causes people to question EVERY
> precept you lay down?
Questioning is fine, but only when it is a genuine attempt to learn or
to establish possible weaknesses and error in the analysis. However,
much of it ranges from the ridiculous to the impossible. Other than
that, you'd be better off ignoring the _style_ and considering the
_content_ of what's been written. Scientists tend to be socially
maladjusted misfits, I'll not bring up any of the famous examples for
obvious reasons but don't be under any illusion that the insignificant
nobodies are much better. For that matter, cyclists are an odd bunch
too, and the combination is definitely unhealthy. Readers in the UK
may consider Adam Hart Davies at this point!
> Except that the only verifiable evidence is the very short blurb in
> STW about the axle moving in the drop out. I'd be a little slower to
> claim victory if I were you.
>
> > Every aspect of the failure has been replicated in detail
> > under repeatable conditions.
>
> LOL. An outright lie.
You could at least consider the possibility that you have not seen all
the evidence before rubbishing my statements.
James
Super Slinky
> Perhaps that is true, and it is really only this point that prompted
> me to reply again. The rest of the nonsense can be left floating as a
> testament to your determined stupidity.
Translation: I have been fully answered and my arguments have been shown
to be weak and biased propaganda designed to deceive the ignorant.
Therefore I will resort to ad hominem attacks to draw away attention
from my failure to present a convincing case for this alleged emergency
that nobody besides me really cares much about. Really though, if you
used the same type of charm and debating skills with the manufacturers
and the CPSC, it is no wonder that you got the bum's rush.
> There are always bigger fish to fry. If I could have the last 6 months
> back, and use them to find a cure for cancer or solve the problem of
> world poverty, then I certainly would take those over my relatively
> minor discovery. But that's not the way things work. I worked on this
> problem because it had affected me directly, and it certainly seemed
> important enough to me to be worth dealing with. In contrast to the
> bigger fish above, it didn't seem like anyone else was doing anything.
You have admitted that your accident contained a number of freakish
circumstances which I have spelled out several times, yet here it crops
up again as a warning to the world of what great danger we are in.
Moreover, the key point of your complaint the way it currently stands
(the lame, unproven, and far-fetched skewer unscrewing theory) did not
happen to you, as I have also pointed out.
> Snip
> James
You speak as if you are going to bring the world to its knees, but you
haven't given much indication what this is all leading up to. I suppose
the ultimate fruit of your labor is a lawsuit, since there must be an
ulterior motive to all your kindness and generosity in saving the world
from these evil manufacturers. So it would seem from the above
statements and other comments you have made such as 'betting your
house'. It would go a long way toward explaining the lengths you have
gone to in order to scare up what scant support you have, your
disgraceful treatment of those who disagree with you, and your generally
creepy behavior. Just follow the money, as they say, and everything will
be explained. I only hope that I haven't somehow helped you.
Anyway, I would like to say that it has been nice corresponding with
you, but it hasn't. Since you have proven to be an abusive lowlife, I
can only hope that you fall on your face and be shown as the con artist
that you are.
> PS Oh, happy to hear about your fork. It reminds me of someone else
> who rode a Fox fork hard for several months, with no problems. This
> person also told me (last December) that they didn't believe disk
> brakes could cause this problem. At the time, this attitude was
> completely reasonable and widely shared as no-one had explained the
> phenomenon, and the circumstantial evidence of a problem was rather
> weak (although IMO enough to be worrying). That's not true any longer.
Yes, we all know about Russ Pinder's accident and the fact that nobody
knows what actually happened. I wonder if he knows that you go around
beating people over the head with his misfortunes. Again you make your
sleaziness embarrassingly obvious to everyone but yourself.
James Annan
> (the lame, unproven, and far-fetched skewer unscrewing theory)
Unproven since the 1960s, as lamely described on this far-fetched web
site:
http://www.boltscience.com/pages/vibloose.htm
and not brought bang up-to-date a few weeks ago with this irrelevant
demonstration that has absolutely nothing whatsoever to do with
unscrewing of QR skewers:
http://kinetics.org.uk/html/disc_brakes___qrs.html
> I suppose
> the ultimate fruit of your labor is a lawsuit, since there must be an
> ulterior motive to all your kindness and generosity in saving the world
> from these evil manufacturers.
You tried this ridiculous smear a couple of months ago, and you'll get
the same response next time too: there's no money in this for me, from
lawsuits or otherwise. Don't judge everyone by your own standards.
> Yes, we all know about Russ Pinder's accident and the fact that nobody
> knows what actually happened. I wonder if he knows that you go around
> beating people over the head with his misfortunes.
I don't expect that he, or anyone else for that matter, agrees with
every word I have said - in fact, I'm not sure that even I agree with
every word that I've said - but what I've heard from him and his
friends has been generally supportive. If you or anyone else wants to
see what he said not long ago try reading this:
http://www.singletrackworld.co.uk/forum/read.php?f=2&i=523608&t=523608#reply_523608
James
Spider
> Super Slinky <sli...@newmail.net> wrote in message news:<MPG.19c1c85c7...@netnews.comcast.net>...
>
> > (the lame, unproven, and far-fetched skewer unscrewing theory)
>
> Unproven since the 1960s, as lamely described on this far-fetched web
> site:
>
> http://www.boltscience.com/pages/vibloose.htm
What has this to do with cammed, knurled-surface QRs, again?
> and not brought bang up-to-date a few weeks ago with this irrelevant
> demonstration that has absolutely nothing whatsoever to do with
> unscrewing of QR skewers:
>
> http://kinetics.org.uk/html/disc_brakes___qrs.html
If you think that this website actually supports your hypothesis, you
haven't read it. His one (1) experiment with a Ti skewer is not
representative.
His conclusions are about the same as the most of the MTB community
that has read your hypothesis.
> > I suppose
> > the ultimate fruit of your labor is a lawsuit, since there must be an
> > ulterior motive to all your kindness and generosity in saving the world
> > from these evil manufacturers.
>
> You tried this ridiculous smear a couple of months ago, and you'll get
> the same response next time too: there's no money in this for me, from
> lawsuits or otherwise. Don't judge everyone by your own standards.
You are the one who seems to bring "court of law" into the discussions
most often. If that portion is not important, don't bring it up. In
any case, your motivations are certainly not as clear as you pretend
they are.
> > Yes, we all know about Russ Pinder's accident and the fact that nobody
> > knows what actually happened. I wonder if he knows that you go around
> > beating people over the head with his misfortunes.
>
> I don't expect that he, or anyone else for that matter, agrees with
> every word I have said - in fact, I'm not sure that even I agree with
> every word that I've said - but what I've heard from him and his
> friends has been generally supportive. If you or anyone else wants to
> see what he said not long ago try reading this:
>
> http://www.singletrackworld.co.uk/forum/read.php?f=2&i=523608&t=523608#reply_523608
His opinion, after having read your hypothesis, is worth very little
in describing what actually happened, because, as has been pointed out
previously, on numerous occasions, the initial conditions are not
known *with certainty.*
Spider
Spider
> beelz...@hotmail.com (Spider) wrote in message news:<73da2590.03090...@posting.google.com>...
> > still_th...@hotmail.com (James Annan) wrote in message news:<c96ea403.0309...@posting.google.com>...
>
> > > Nevertheless, it moves, and has been directly measured by several
> > > cyclists and scientists, including the Velotech testing lab in
> > > Germany.
> >
> > The "several cyclists" aren't scientists,
>
> Some are scientists, some are cyclists, some are both and quite
> possibly some are neither.
And which are which? What were the experimental conditions? What
equipment was used? Sorry, James, but these "insignificant details"
are what makes an account worthwhile or worthless.
> > and the initial conditions
> > are not controlled
>
> False
OK, you go right ahead a point out the link to where the tension of
the QR was measured first. What was it? What was the brand and type
of QR used? Hub? I don't think that even the Velotech guys have
published that data, or any other thing, other than "the axle moved".
So, rather than "false," my contention is "true."
> > and not known.
>
> to you.
Or you. If you had data, you'd publish it. But you don't.
> > If indeed the QR retention method is judged to be adequate by
> > the German lab, I suppose all that will be left for you is to raise
> > money for your planned class-action lawsuit.
>
> I'm not planning any lawsuit, I have an apology from the builder of my
> fork and I am confident he will not make the mistake again. I have no
> paticular desire to cripple small businesses but I do want the problem
> solved.
If there is indeed a "problem." While I agree with you and Jobst that
the ejection force is an undesirable consequence of the
rear-positioned brake caliper, I do not yet see it as anything more
than a design compromise.
> > Or maybe your antagonistic style causes people to question EVERY
> > precept you lay down?
>
> Questioning is fine, but only when it is a genuine attempt to learn or
> to establish possible weaknesses and error in the analysis.
No, *all* questioning is fine. If you are right, then all the
buttheads who are just being asses will be discredited as such in the
long term. All those folks who are trying to establish exactly what
the failure mode is, and how it might be prevented (in whatever
fashion) and how serious the potential problem might be - all of us
deserve straightforward answers, without the sneering condescension.
You may think you are the cat's pajamas, and others may agree, but
this isn't about your self-image.
> However,
> much of it ranges from the ridiculous to the impossible.
Then point them to your webpages, which should have all the answers
printed. If it doesn't, the fault is not in the questioner, but in
the questioned.
> Other than
> that, you'd be better off ignoring the _style_ and considering the
> _content_ of what's been written.
Frankly, you'd be better off being a bit more humble. You are trying
to convince people that you are correct, so it behoove you to act as
though you want their support. If this is the way you communicate,
then your message will be ignored as roundly as MV's - because even
though he has a point buried under all the crap he spews, nobody
listens due to the style of presentation.
There's a saying that mothers and fathers have used for a long time:
"It's not what you say, it's how you say it."
> Scientists tend to be socially
> maladjusted misfits, I'll not bring up any of the famous examples for
> obvious reasons but don't be under any illusion that the insignificant
> nobodies are much better.
I don't care one way or another what your excuses might be. If you
want support, you have to be willing to be, at the very least,
somewhat polite.
> For that matter, cyclists are an odd bunch
> too, and the combination is definitely unhealthy. Readers in the UK
> may consider Adam Hart Davies at this point!
Again, being a cyclist is no excuse to sneer at those who are not.
Does the analogy work for you, or must I be more explicit?
> > Except that the only verifiable evidence is the very short blurb in
> > STW about the axle moving in the drop out. I'd be a little slower to
> > claim victory if I were you.
> >
> > > Every aspect of the failure has been replicated in detail
> > > under repeatable conditions.
> >
> > LOL. An outright lie.
>
> You could at least consider the possibility that you have not seen all
> the evidence before rubbishing my statements.
Since you have not published the data, then AFAIK, it doesn't exist.
Since you are so quick to tout even the slightest support for your
hypothesis, it doesn't strike me that you'd hold back vital data for
even a nanosecond.
Let's see the data, the test methods and the materials. If you have
something I've not seen previous, then show it, and you'll have my
apologies, in public.
Otherwise, my comment stands as written.
Spider
James Annan
> > http://www.boltscience.com/pages/vibloose.htm
>
> What has this to do with cammed, knurled-surface QRs, again?
Hey, it didn't mention the colour or any other irrelevant detail. Why
not mention the purple anodising too?
> > and not brought bang up-to-date a few weeks ago with this irrelevant
> > demonstration that has absolutely nothing whatsoever to do with
> > unscrewing of QR skewers:
> >
> > http://kinetics.org.uk/html/disc_brakes___qrs.html
>
> If you think that this website actually supports your hypothesis, you
> haven't read it. His one (1) experiment with a Ti skewer is not
> representative.
>
> His conclusions are about the same as the most of the MTB community
> that has read your hypothesis.
His conclusion is that the CPSC had better not look into it carefully,
because he has seen that there is a real problem.
> In
> any case, your motivations are certainly not as clear as you pretend
> they are.
I'd be grateful if you could help me out and tell me what they are.
Oh, and while you're doing the mindreading, how about telling me what
I'm having for breakfast next Tuesday.
James
Super Slinky
> Unproven since the 1960s, as lamely described on this far-fetched web
> site:
>
> http://www.boltscience.com/pages/vibloose.htm
But they aren't talking about bicycle skewers, are they? Bicycle skewers
have safeguards against just this sort of thing happening. The heavily
knurled surfaces in contact with the soft metal of the forks are going
to be a major obstacle. I also noticed that my bolt-on skewers have a
buffer against your purported unscrewing mechanism. The allen head spins
freely inside the cup that has the knurled surface that clamps to the
dropouts. This will isolate it from any torque that might act to unscrew
it if the friction in the threads is greater than the friction of the
allen head against the cup, especially if the allen head is on the same
side as the brake. I don't know which side has more friction, but my
guess is that the threads have more, and consequently this setup isn't
very likely to unscrew, even if we suspend disbelief and accept your
theory as fact. This effect can be enhanced by putting graphite in the
cup and allen head interface and using thread lock on the threaded side.
> and not brought bang up-to-date a few weeks ago with this irrelevant
> demonstration that has absolutely nothing whatsoever to do with
> unscrewing of QR skewers:
>
> http://kinetics.org.uk/html/disc_brakes___qrs.html
With all due respect to the author of the article, I'm sure he's a nice
guy and means well, but this ranks among the most superficial and
unscientific 'experiments' I have ever heard of. I'm surprised you
bothered to point it out. He wants to see if there is unscrewing
happening, but he didn't even do something as basic as putting matching
hash marks on the fork and skewer or checking the dropouts for telltale
signs of wear. If a properly tightened skewer is forced to move in the
dropouts, IT WILL DAMAGE THE DROPOUTS. I really don't know how to make
it any plainer. If this were happening as often as you claim, then we
would all see it and it would have been thoroughly discussed before now.
Aside from that, he didn't come down very hard on your side. He said
that his QR and disc brake combo hadn't loosened in a year and a half of
riding when tightened to his own satisfaction. He also said the effect
disappeared when the cam lever was installed on the left. I can't think
of a reason why this would nullify the alleged unscrewing effect,
because a QR isn't isolated from the clamp surface the way the allen
head in my bolt-on skewer is. But I suppose there would be some
isolation since they aren't welded together.
> I don't expect that he, or anyone else for that matter, agrees with
> every word I have said - in fact, I'm not sure that even I agree with
> every word that I've said - but what I've heard from him and his
> friends has been generally supportive. If you or anyone else wants to
> see what he said not long ago try reading this:
>
> http://www.singletrackworld.co.uk/forum/read.php?f=2&i=523608&t=523608#reply_523608
>
> James
Russ's accident was a tragic thing to be sure. That it could have been
any one of us makes it hit even closer to home. As such, it would have
been hard to chime in on that discussion with a dissenting point of
view. You seem to focus much of your attention on downhill accidents,
like what happened to Russ. Downhill is certainly the most dangerous
part of a ride and the brakes play a key role there, but a small problem
with that hang up is that a downhill is the last place we would see the
maximum brake ejection force. Brakes must be used judiciously and gently
going downhill, or you will just skid out the front wheel or endo. Going
downhill, the friction available to the wheels will be smaller, and
since you are already at an angle, less force will be required to
produce an endo. You will see the maximum ejection force on level
ground. So your proposed loosening isn't likely to start on the downhill
if the skewer stayed tight through the rest of the ride. The only thing
you can say is that if the skewer is already loose, the downhill can
quickly provide the agitation to finish it off.
I'm not going to say I know what happened in this accident. It sounds to
me like it all happened so fast that nobody knows how it unfolded. This
is typical of most of my own comparatively minor trail accidents, as I
have said previously. I'm being perfectly honest when I say that until
there is more evidence in your favor, I don't see how you are doing
anyone any favors by linking this accident to your theories. In spite of
your condescending arrogance, you have failed to impress the CPSC, or
anyone else with the power to affect change, that there is any hard
evidence in support of your claims. But carry on like you have. I'm sure
the whole thing will die of apathy and be forgotten soon enough.
Spider
> beelz...@hotmail.com (Spider) wrote in message news:<73da2590.03090...@posting.google.com>...
> > still_th...@hotmail.com (James Annan) wrote in message news:<c96ea403.03090...@posting.google.com>...
>
> > > http://www.boltscience.com/pages/vibloose.htm
> >
> > What has this to do with cammed, knurled-surface QRs, again?
>
> Hey, it didn't mention the colour or any other irrelevant detail. Why
> not mention the purple anodising too?
Hmmm, here's a couple of "irrelevant details" from the website you
gave:
"Through the efforts of the American National Standards Subcommittee
B18:20 on locking fasteners, three basic locking fastener categories
have been established. They are: free spinning, friction locking, and
chemical locking.
The free spinning type are plain bolts with a circumferential row of
teeth under the washer head. These are ramped, allowing the bolt to
rotate in the clamping direction, but lock into the bearing surface
when rotated in the loosening direction. The "Whizlock" is in this
category."
And,
"In general terms, the key to preventing self loosening of fasteners
is to ensure that :
1. There is sufficient clamp force present on the joint interface to
prevent relative motion between the bolt head or nut and the joint.
..."
Now, let's see here - knurling, and a cam-activated mechanical
advantage lever to get more clamping. How odd that you would consider
these two important parts of the QR irrelevant.
You are nearly Vandemanesque in your ability to see the data you like,
and "not see" the data that inconvenient. Perilously close to what is
know as "junk science."
> > > and not brought bang up-to-date a few weeks ago with this irrelevant
> > > demonstration that has absolutely nothing whatsoever to do with
> > > unscrewing of QR skewers:
> > >
> > > http://kinetics.org.uk/html/disc_brakes___qrs.html
> >
> > If you think that this website actually supports your hypothesis, you
> > haven't read it. His one (1) experiment with a Ti skewer is not
> > representative.
> >
> > His conclusions are about the same as the most of the MTB community
> > that has read your hypothesis.
>
> His conclusion is that the CPSC had better not look into it carefully,
> because he has seen that there is a real problem.
Here is the only thing he actually said about the CPSC:
"The CPSC in the States is investigating, but they have not been the
most balanced cycling test body on previous occasions."
He also says this:
"Unlike James Annan, I do not believe that there is a fatal design
flaw with *all* combinations of disc brake, fork and quick release."
In his conclusions, he says this:
"There are three levels of solution, depending on how paranoid you are
feeling at the moment...
Level 1 paranoia: (cheap or no-cost DIY solutions)
*
Use a good quality branded skewer from one of the major
manufacturers - make sure that it has good serrations and that the
lever action feels smooth and has a definite "clunk" as you close it.
*
Fit the skewer with the lever on the left side. This means that
the entire skewer has to turn, instead of just the nut, making visual
checks easier.
*
Close the lever as hard as you can manage by hand - it should
leave a definite imprint in your palm (if you use your palm). If you
don't have that much hand strength, lay the bike on it's side and
stand on the lever, but don't go OTT.
*
Make sure that the lever is not touching anything when it's
closed - it should not be touching the fork leg, for example. I know
it's not as neat, but closing the skewer so it points horizontally
backwards is the best way.
*
Use a releasable cable tie to sttach the lever to the fork leg,
to stop it flipping open.
Level 2 paranoia: (cheap low-hassle aftermarket solutions)
*
Several manufacturers are producing (or have on the drawing
board) various types of locking skewer. These could be a good idea,
assuming that they lock with enough force, as they'd prevent any
vibration loosening.
*
Use a solid axle nutted hub instead. The clamping force of a
10mm nut is much higher than that of a QR skewer, which is why track
bikes use them.
Level 3 paranoia: (serious bombproof solutions)
*
Use a bolt-through front hub. This requires new forks and a new
wheel, but is totally solid.
*
Several manufacturers are introducing forks with forward-facing
dropouts - this means that the ejection force is no longer pushing the
axle out of the slot.
*
Use forks with the caliper on the front of the right fork leg.
This alters the angle of the force so it is no longer a problem. This
would require a custom fork, of course.
Personally, I'm a level 1 person..."
No, James, he just doesn't agree that this is an earth-shattering
problem. THe fact that you would misrepresent his analysis speaks to
your obfuscation on the issues.
> > In
> > any case, your motivations are certainly not as clear as you pretend
> > they are.
>
> I'd be grateful if you could help me out and tell me what they are.
Well, that a clever bit of irony, but considering the other two claims
that you have made in this last post of yours, shown to be hilariously
misleading at best, your claims of purity of motivation strike me as
hollow, tending toward disingenuous. I won't call you a deliberate
liar, because I do not know if this is the case of not. But your
communication style has again gotten in the way of your message, and
you are doing your best to alienate the folks you should be trying to
recruit.
My apologies for quoting so much material - I just wanted to be clear
that what James says, and what is actually written, can be two
entirely different things.
Spider
James Annan
> "In general terms, the key to preventing self loosening of fasteners
> is to ensure that :
>
> 1. There is sufficient clamp force present on the joint interface to
> prevent relative motion between the bolt head or nut and the joint.
Exactly. That's the key. When the clamp force prevents movement,
you're fine, but when it fails to prevent movement, then unscrewing
can be expected to happen.
Knurling and a high clamp force will help reduce the tendency to slip,
but they are no guarantee, as all observations of slippage have found.
That's not to say slippage will occur on _every_ fork, but it has been
seen on plenty of them. The QR is not designed to withstand this force
- check the ISO standard and ask the skewer manufacturers if you
disagree.
> > His conclusion is that the CPSC had better not look into it carefully,
> > because he has seen that there is a real problem.
>
> Here is the only thing he actually said about the CPSC:
>
> "The CPSC in the States is investigating, but they have not been the
> most balanced cycling test body on previous occasions."
No, that's not true. Again you are falling into the trap of assuming
that because you have not read it, it does not exist and is not true.
"It's good that the CPSC have decided not to investigate - if they
did, you could probably have kissed goodbye to mountain biking in it's
current form.
This isn't to say that the problem can be safely ignored - it isn't.
Manufacturers are working on fixes for the next model year (2005) -
until then, use one of the safety bodges - like my hose clip ;-)"
http://www.singletrackworld.com/forum/read.php?f=2&i=553910&t=553505#reply_553910
I think he is scaremongering, which is amusing as he has spent several
months accusing me of the same. The comment about the manufacturers
fixing the problem in 2005 has been also made by a couple of
journalists interested in the issue. The only real question seems to
be whether they will get away with selling these designs for another
year.
James
James Annan
> But they aren't talking about bicycle skewers, are they? Bicycle skewers
> have safeguards against just this sort of thing happening. The heavily
> knurled surfaces in contact with the soft metal of the forks are going
> to be a major obstacle.
They are talking about threaded bolts in general, which includes
skewers. They specifically mention the value of knurling, but it's
clear that the mechanism by which this works (when it does) is by
preventing movement. When it fails to prevent movement, it won't
prevent unscrewing either.
> I also noticed that my bolt-on skewers have a
> buffer against your purported unscrewing mechanism.
I'm not talking about your skewers. Perhaps this is why you've been so
hostile - did you think I was telling you that _your_ skewers were
slipping and unscrewing, and you had failed to notice? Of course I
believe you when you say this has not happened. All I have been trying
to say is that _some_ skewers have been seen to slip and unscrew, even
when correctly used.
> > http://kinetics.org.uk/html/disc_brakes___qrs.html
>
> With all due respect to the author of the article, I'm sure he's a nice
> guy and means well, but this ranks among the most superficial and
> unscientific 'experiments' I have ever heard of.
I agree, but he happens to be the only person (that I know of) who has
bothered to (a) measure the unscrewing repeatedly, and (b) put up a
web page about it. So it's a handy reference. Unless you think he's
lying, or too incompetent to make this simple observations, it's hard
to avoid the conclusion that his skewer did, in fact, unscrew.
> If a properly tightened skewer is forced to move in the
> dropouts, IT WILL DAMAGE THE DROPOUTS.
Probably there will be some fretting, yes. I'm not sure what point you
are trying to make here. Unless you think that the velotech lab faked
their measurements (and even photos too) then their skewer certainly
moved. In fact Ernst Brust says he has known about this skewer
movement for several years and has warned manufacturers, but they have
ignored him. Although IMO this alone is prima facie evidence of a bad
design (the axle isn't supposed to move under ordinary braking forces)
it seems like no-one had previously thought of the potential for
unscrewing from repeated transverse movement, so the danger wasn't
apparent.
> I really don't know how to make
> it any plainer. If this were happening as often as you claim, then we
> would all see it and it would have been thoroughly discussed before now.
I haven't made any strong claim as to the frequency. It happens to
some people, and to a subset of them, it's a very real problem.
> Downhill is certainly the most dangerous
> part of a ride and the brakes play a key role there, but a small problem
> with that hang up is that a downhill is the last place we would see the
> maximum brake ejection force. Brakes must be used judiciously and gently
> going downhill, or you will just skid out the front wheel or endo. Going
> downhill, the friction available to the wheels will be smaller, and
> since you are already at an angle, less force will be required to
> produce an endo. You will see the maximum ejection force on level
> ground. So your proposed loosening isn't likely to start on the downhill
> if the skewer stayed tight through the rest of the ride. The only thing
> you can say is that if the skewer is already loose, the downhill can
> quickly provide the agitation to finish it off.
Certainly hard braking on level ground can provide exceptionally large
momentary forces - this is why Planet-X recently changed the angle of
their dropouts, since rider(s) (cerainly Brant Richards, another vocal
critic of me, has reported it, and they give this explanation on their
website) can move the front wheel when doing low-speed stoppies.
Some people have reported loosening under rather tame testing (like
Ben Cooper) but it seems reasonable to me that fast rough downhill is
particularly testing as it will can generate lots of up and down
forcing in a very short interval of time. There needs to be
significant upwards forcing too, as the steady force of body weight
alone will probably not be enough to move the axle back up to the
correct position. Hitting bumps fast can certainly provide that. I
don't see any reason why friction itself is reduced by a slope, and it
takes a very steep slope to prevent firm front brake use if the
terrain is reasonably firm.
> I'm sure
> the whole thing will die of apathy and be forgotten soon enough.
Planet X and a couple of tandem builders have already made design
changes, rumour has it that Pace may do for next year and (according
to the journalists involved) the major manufacturers have all but
promised it for 2005 in the hope that the journalists will shut up
about it. That doesn't sound like apathy to me. In fact it seems to me
that things are pretty well wrapped up except for how to deal with the
forks in use and being sold at the moment. That's where the debate
should be, not on whether the problem exists at all.
James
Super Slinky
> I'm not talking about your skewers. Perhaps this is why you've been so
> hostile - did you think I was telling you that _your_ skewers were
> slipping and unscrewing, and you had failed to notice? Of course I
> believe you when you say this has not happened. All I have been trying
> to say is that _some_ skewers have been seen to slip and unscrew, even
> when correctly used.
I guess that is part of the problem and where a lot of the disagreement
is. If this is true, maybe more energy should have been spent trying to
see what their specific problem is and how it can be remedied using what
we have available to us now. After looking at my bolt-on skewers, I
think that most of your concerns, whatever merit they may have, can be
addressed with skewer design. If the QR cam lever and nut were isolated
from the clamping surfaces, and the nut was a locking design that had
more friction with the threads, your proposed unscrewing mechanism would
have another major obstacle to overcome. When combined with retention
lips, a skewer like this would have the even better safety benefit of
making it far less likely to loose the wheel if the rider forgot to
tighten it or tightened it inadequately. It wouldn't as easily unscrew
the rest of the way from vibration, no matter what brake system was
used. But a simple fix like this begs the question why it hasn't already
been done. The obvious answer is that very few people have a problem
with skewers the way they are now. It would be more expensive skewer
with more parts to lose and it would be harder to get on and off. Would
anyone want it or pay extra for it?
Another shameful consequence of you trying to railroad through wholesale
changes to a design that appears to be safe and functional for almost
everyone might be that new designs may turn out to be ultimately less
safe than what we have now. Since countless thousands of people have
been using the current design with so few problems, how long is it going
to take us to really know if there has been a net gain in safety? If new
designs cause twice as many accidents as we have now, who will ever know
if there isn't another media induced hoopla to point it out? We would
never know about the unintended consequences of increasing costs or
diverting scant engineering and tooling resources toward this instead of
something else that might be even more beneficial.
> I agree, but he happens to be the only person (that I know of) who has
> bothered to (a) measure the unscrewing repeatedly, and (b) put up a
> web page about it. So it's a handy reference. Unless you think he's
> lying, or too incompetent to make this simple observations, it's hard
> to avoid the conclusion that his skewer did, in fact, unscrew.
That is your take on it. Mine is different. I don't think there is
enough information there to make it noteworthy.
> Probably there will be some fretting, yes. I'm not sure what point you
> are trying to make here. Unless you think that the velotech lab faked
> their measurements (and even photos too) then their skewer certainly
> moved. In fact Ernst Brust says he has known about this skewer
> movement for several years and has warned manufacturers, but they have
> ignored him. Although IMO this alone is prima facie evidence of a bad
> design (the axle isn't supposed to move under ordinary braking forces)
> it seems like no-one had previously thought of the potential for
> unscrewing from repeated transverse movement, so the danger wasn't
> apparent.
The point I'm trying to make is that this is the smoking gun if there is
one. It is physical evidence, not anecdotes, not amateurish experiments
or force equations. If properly tightened skewers are being jerked
around as you say, then damage to the dropouts will be seen. There would
be a clear difference between the condition of the brake side dropout
and the right side dropout. The paint would be stripped away and there
would be an oval shaped wear pattern with considerable scoring of the
metal on the fork leg and metal shavings. If you had been producing this
kind of evidence from the start, then you would have something.
You keep repeating the Velotech testing as if it is irrefutable proof of
what you say, but I'm not so easily impressed by one lab in a foreign
country doing tests using equipment and conditions that I know nothing
about. Nor do I accept your implication that what they have done is
somehow infallible or above reproach. I don't know what their reputation
is, how they are funded, if they are audited or regulated or anything
else that might shed some light on what they are trying to prove. I work
in a testing lab and I know how difficult it can sometimes be to produce
data that is free from error or flawed test methods. What I have heard
about the Velotech testing hasn't made me want to go buy a thru-axle
fork just yet. The last I heard the testing was incomplete and merely
showed that the axle moved under brake load. You proved more than that
with your accident and the resulting photos. It didn't say they had been
able to get a skewer to unscrew, which you claim is the basic threat, or
that they had even been able to show that there is up and down movement.
> Certainly hard braking on level ground can provide exceptionally large
> momentary forces - this is why Planet-X recently changed the angle of
> their dropouts, since rider(s) (cerainly Brant Richards, another vocal
> critic of me, has reported it, and they give this explanation on their
> website) can move the front wheel when doing low-speed stoppies.
I looked at the Planet-x forks and I saw that they shared most of the
unfortunate design qualities of your tandem fork--lack of retention
lips, rearward facing dropouts, steel construction. Not that there is
anything wrong with steel, but the vast majority of disc brakes are
mounted to magnesium suspension forks which would provide a better grip
for the skewer.
> Some people have reported loosening under rather tame testing (like
> Ben Cooper) but it seems reasonable to me that fast rough downhill is
> particularly testing as it will can generate lots of up and down
> forcing in a very short interval of time. There needs to be
> significant upwards forcing too, as the steady force of body weight
> alone will probably not be enough to move the axle back up to the
> correct position. Hitting bumps fast can certainly provide that. I
> don't see any reason why friction itself is reduced by a slope, and it
> takes a very steep slope to prevent firm front brake use if the
> terrain is reasonably firm.
The frictional force available from the ground on the slope is reduced
by multiplying the weight of the bike and rider by the cosine of the
angle of the slope. On level ground, you get all of the frictional
force. Falling off a cliff, the friction of the cliff face is irrelevant
because you have no weight pressing against it. Level ground: Cos(0º)=1,
falling off a cliff: cos(90º)=0. On a 25º slope, 10% of the maximum
braking force is lost. The slope also raises the center of gravity
relative to the axle, decreasing the force required to produce an endo,
and consequently reducing maximum braking force yet again by the same
factor. All if this is in addition to the fact that the typical
coefficient of friction of a dirt trail will always be much less than on
pavement. To sum it all up, the largest maximum braking force will be
seen on level pavement and the smallest maximum braking force would be
on a downhill slope off-road. My point is that your proposed unscrewing
mechanism isn't likely to start on a downhill.
The force required to move the axle back up if it is forced down from
its original position by braking force is also a very important
question, as Joe Riel pointed out in r.b.t. We know that the downward
force must be considerably greater than the upward force, or your brake
induced movement of the axle can't happen. In addition to that, the
upward force will increase to its maximum at the same time that the
downward force is approaching its critical point, because all of the
weight of the bike and rider will shift to the front wheel.
But it gets worse. 95-99% of disc brakes are mounted to suspension
forks. This means that the almost all the weight on a front axle is
sprung weight and this greatly decreases the upward forces generated.
That is what a suspension does, and that is why the upward force needed
to produce that up and down unscrewing motion of yours may not be
possible, because the upward force must also overcome the clamping force
of the skewer and there is a very limited amount of upward force
available.
> Planet X and a couple of tandem builders have already made design
> changes, rumour has it that Pace may do for next year and (according
> to the journalists involved) the major manufacturers have all but
> promised it for 2005 in the hope that the journalists will shut up
> about it. That doesn't sound like apathy to me. In fact it seems to me
> that things are pretty well wrapped up except for how to deal with the
> forks in use and being sold at the moment. That's where the debate
> should be, not on whether the problem exists at all.
Whatever. If this is true, then I guess we can thank you for increasing
our costs and possibly delaying other innovations that might have proved
more useful.
Doug Taylor
>Planet X and a couple of tandem builders have already made design
>changes, rumour has it that Pace may do for next year and (according
>to the journalists involved) the major manufacturers have all but
>promised it for 2005 in the hope that the journalists will shut up
>about it. That doesn't sound like apathy to me. In fact it seems to me
>that things are pretty well wrapped up except for how to deal with the
>forks in use and being sold at the moment. That's where the debate
>should be, not on whether the problem exists at all.
All contributors to these Annan Principal threads are starting to
sound like broken records.
I'll repeat my main point one more time:
The "problem" - assuming it IS a problem - is a relatively
insignificant one as far as the bicycle industry is concerned: it's
frequency of occurrence is negligible when viewed against the total
number disc brake equipped mountain bikes with QR's in use. No huge
lawsuits have been filed; no horrible publicity has been generated a
la Ford Pinto and Firestone tires. Moreover, the CPSC, having been
alerted to the issue by Annan, has determined there is insufficient
evidence to date in order to determine the brake/fork/QR configuration
constitutes a "substantial product hazard" under Section 15 of the
CPSA.
Consequently, the industry has no incentive whatsoever voluntarily to
recall or modify existing equipment is use. It would be prohibitively
expensive and would "kill" the industry. Future equipment may well
incorporate designs to eliminate any hint or questions of wheels being
ejected due to disc brake forces. But until such time as it becomes
more cost effective to recall the existing product than to maintain
the status quo (huge lawsuits) or the CPSC requires it, there will be
NO change in the status quo and NOTHING will be done about forks in
use and sold at the moment.
You can take that to the bank,
--dt
Doug Taylor
>Now if Joe Machineshop comes up with this magical design that clamps
>with 5 times the force and fits in a standard droupout/hollow axle, Joe
>might make a ton of money capitalizing on this problem that doesn't
>exist, thanks to his unwitting lackys. Joe would do well not to let
>this greed get the best of him and skip out to the Bahamas before
>collective damage his design has caused to frames everywhere becomes
>evident.
His name is "James," not Joe.
--dt