Disc brakes and QRs making headlines
Tim McNamara
appears to have had an impact (no pun intended) and was mentioned
today on Peter Eland's VeloVision Magazine Web site:
Eland mentions that the concern has been taken up on the BikeBiz
industry Web site. I looked and there's nothing I could find in the
consumer pages, but there seems to be possibly something in the
industry pages.
James's Web site is at:
http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/index.
html
Doug Huffman
bike media drives hysteric concerns. Words no longer mean much unless they
are piled high and deep. The conspiracy of ignorance masquerades as common
sense.
People have forgotten the significance of words like 'may' and 'possibly'
and 'anecdote'. My disk brakes have been reliable for >20K miles.
"Tim McNamara" <tim...@bitstream.net> wrote in message
news:timmcn-ED6E81....@gemini.visi.com...
James Annan
> Eland mentions that the concern has been taken up on the BikeBiz
> industry Web site. I looked and there's nothing I could find in the
> consumer pages, but there seems to be possibly something in the
> industry pages.
Yes, it's on the password-protected bit:
http://www.bikebiz.co.uk/web/article.php?id=2899
Is this the end of QRs for MTBs?
A Scottish climate research scientist based in Japan has stirred up a
hornet's nest of a safety topic. James Annan claims quick release
skewers are no longer 'fit for purpose' on disc-brake equipped bikes.
They can and do come undone, says Annan. Riders have so far put this
down to their own sloppiness but a recent crash, which left an English
rider disabled, has brought the issue into sharp focus. Manufacturers
have been dismissive of Annan's emails to date but a growing number of
engineering-trained bike experts are lining up behind Annan's theories.
Cigarette companies, aware of tobacco-related illnesses since the 1950s
onwards, were successfully sued in group actions because of the wilful
disregard of evidence that tobacco harms. If the QR problem is ignored,
could the bike trade be crippled by similar lawsuits?
(etc, with more in the same vein - nothing factually different from what
has been said on my website and rec.bicycles.tech)
> James's Web site is at:
>
> http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/index.
> html
James
David Kunz
> news:timmcn-ED6E81....@gemini.visi.com...
>
>>James Annan's Web site about disc brakes and disengaging front wheels
>>appears to have had an impact (no pun intended) and was mentioned
>>today on Peter Eland's VeloVision Magazine Web site:
>>
>>http://www.velovision.co.uk/
>>
>>Eland mentions that the concern has been taken up on the BikeBiz
>>industry Web site. I looked and there's nothing I could find in the
>>consumer pages, but there seems to be possibly something in the
>>industry pages.
>>
>>James's Web site is at:
>>
>>http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/index.
>>html
Doug Huffman wrote:
> Just as the 'media' drives hysterical concerns in the US for its profit, the
> bike media drives hysteric concerns. Words no longer mean much unless they
> are piled high and deep. The conspiracy of ignorance masquerades as common
> sense.
>
> People have forgotten the significance of words like 'may' and 'possibly'
> and 'anecdote'. My disk brakes have been reliable for >20K miles.
>
Unfortunately, "may" and "possibly" means to lawyers that the companies
know about the "problem" and therefore are liable for any consequences
to the limit that a jury may make it reach into it's pockets (plus
expenses). I'm really tired of the US legal system and the people who
exploit if for their own selfish ends.
David
W K
"Doug Huffman" <dhuf...@awod.com> wrote in message
news:b9t4e0$mg2m8$1...@ID-77170.news.dfncis.de...
> Just as the 'media' drives hysterical concerns in the US for its profit,
the
> bike media drives hysteric concerns. Words no longer mean much unless
they
> are piled high and deep. The conspiracy of ignorance masquerades as
common
> sense.
>
> People have forgotten the significance of words like 'may' and 'possibly'
> and 'anecdote'. My disk brakes have been reliable for >20K miles.
Have you actually looked at the physics behind it?
It definately makes sense, and is something the manufacturers should at
least be thinking about.
BTW its not actually a question of the reliability of the brakes.
Stergios Papadakis
> > James's Web site is at:
> >
> > http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/index.
> > html
>
> James
Hi James,
Is there a reason you picked .6 g for your deceleration
in your model calculation? Obviously on some surfaces
the traction is limited, but an experienced MTBer
who gets his weight way back, and chest nearly
to the seat, could easily brake much harder if
the traction is good.
max braking force = rider weight/tan(angle) where
"angle" is the angle above the horizontal of the line
from the front contact patch to the rider's
CG (neglecting the bike weight, of course). .6 g corresponds
to 60 degrees, and I'd guess a rider could get pretty
close to 45 on flat ground, resulting in a 70% greater force.
Stergios
Dave Kahn
(Quoting from http://www.bikebiz.co.uk/web/article.php?id=2899 )
> If the QR problem is ignored, could the bike trade be crippled by
> similar lawsuits?
Not in the sense that Russ Pinder is, no.
--
Dave...
Doug Taylor
>> Just as the 'media' drives hysterical concerns in the US for its profit,
>the
>> bike media drives hysteric concerns. Words no longer mean much unless
>they
>> are piled high and deep. The conspiracy of ignorance masquerades as
>common
>> sense.
>>
>> People have forgotten the significance of words like 'may' and 'possibly'
>> and 'anecdote'. My disk brakes have been reliable for >20K miles.
>
>Have you actually looked at the physics behind it?
>It definately makes sense, and is something the manufacturers should at
>least be thinking about.
I suppose, but since I've had zero problems with my QR in 2 years of
hard riding with discs, I remain about as concerned as I am with mold
in my house. But once the liability lawyers get a hold of it, it will
become another over hyped circus and it will end up costing the
consumer. Forget the lawyer lips: coming soon to your drops:
"lawyer latches"
--dt
James Annan
> Hi James,
> Is there a reason you picked .6 g for your deceleration
> in your model calculation?
It's a pretty standard estimate, and I didn't want to go to extremes -
that would only have led (even more) people to say I was exaggerating
and scaremongering. It's not critical to the calculation.
James
Dion Dock
lips" and leave your front wheel attached for some length of time.
This is like saying you never get a blue screen of death but neglecting to
mention you reboot your computer every two hours.
-Dion
"Doug Taylor" <tayl...@choiceonemail.com> wrote in message
news:7ts4cvon9edm75kpq...@4ax.com...
(Pete Cresswell)
>Have you actually looked at the physics behind it?
A question from the spatial-relationship-challenged: Does the force that wants
to pop the wheel out of the forks get greater or lesser as the diameter of the
disk increases? (i.e. is it greater for 165mm disks or 185mm disks given all
other factors equal?)
-----------------------
PeteCresswell
James Annan
> I suppose, but since I've had zero problems with my QR in 2 years of
> hard riding with discs, I remain about as concerned as I am with mold
> in my house.
That's ok, even stupid people deserve some protection from badly
designed products (in fact if anything it's the stupid people who need
the protection more than those who understand the danger, and may be
able to mitigate it).
> But once the liability lawyers get a hold of it, it will
> become another over hyped circus and it will end up costing the
> consumer. Forget the lawyer lips: coming soon to your drops:
> "lawyer latches"
You might more accurately aim your animosity at the 'engineers' who
built bicycles designed to spit the front wheel out without warning on
a fast descent. What's worse, some of them continue to deny the
problem even once it has been explained to them in words of one
syllable. What does that tell you about their competence and/or
ethical standards? To me, that puts them comfortably lower than
lawyers, who are at least actually supposed to advocate the case of
their client rather than seek the truth.
At least some of them are now starting to take the problem seriously.
It remains to be seen whether they are approaching the problem with a
genuinely open mind, or merely trying to 'prove' that their products
are not at fault.
James
jobst....@stanfordalumni.org
>>Have you actually looked at the physics behind it?
> A question from the spatial-relationship-challenged: Does the force
> that wants to pop the wheel out of the forks get greater or lesser
> as the diameter of the disk increases? (i.e. is it greater for
> 165mm disks or 185mm disks given all other factors equal?)
The force is translated the skid force on the road to a vertical force
that wants to push the axle out of the dropout by a ratio of wheel
diameter to disk diameter (if the caliper is behind the fork).
That translates to the smaller the disc the greater the disengaging
force. I see no physics astute contributors disagreeing with James's
assessment of the problem, only disbelievers who show no reason why it
is not so, other than they haven't crashed yet.
Jobst Brandt
jobst....@stanfordalumni.org
Palo Alto CA
Chris B.
I was corrected on just this point the last time this was discussed.
For a given rate of deceleration, the extraction force will increase
as the diameter of the rotor _decreases_. The larger rotor is a
longer lever so less force needs to be applied to result in the same
torque.
Chris Bird
Stergios Papadakis
Fair enough. Nice work, by the way.
Stergios
Jon Isaacs
>Have you actually looked at the physics behind it?
>It definately makes sense, and is something the manufacturers should at
>least be thinking about.
What makes you think they are not thinking about it?
One thing to realize is the website in question was the result of a crash
involving a bike with no retaining lips. It took a good deal of effort to get
the site owner to be upfront about this.
Jon Isaacs
Doug Taylor
I apologize for my stupidity, but until your theories are backed up by
statistics which prove there is a cost benefit to re-engineering the
system , I remain unconcerned and unconvinced. I certainly have no
plans to change the components on my mountain bike as it is currently
set up, or stop using it.
Time will tell whether I am a lame brain or you are Chicken Little.
--dt
James Annan
Readers are invited to read my FIRST posting on the subject:
and judge the validity of this complaint.
Do you have anything relevant to say on the contents of the website, by
the way? I remember you being rather sceptical at first, but as soon as
I suggested that the QR could unscrew you seemed to go very quiet.
James
Jon Isaacs
>statistics which prove there is a cost benefit to re-engineering the
>system , I remain unconcerned and unconvinced.
>I certainly have no
>plans to change the components on my mountain bike as it is currently
>set up, or stop using it.
>
>Time will tell whether I am a lame brain or you are Chicken Little.
My personal opinion is that with a well designed Lawyer Lip, this should not be
a problem. Another solution is to simply place the brake ahead of the fork,
this way the moment pushes the wheel into the fork rather than away from it.
But the calculations are real and it is a real problem, the question in my mind
is whether the manufacturers have already addressed this issue.
I have a friend with a Novara flat bar road bike with disk brakes. After
reading Jame's pages and discussing them in a previous thread, I wanted to make
sure that the Lawyer Lips had not be filed off on his bike and that he knew the
importance of properly tightening the QR.
I looked at the dropouts and the the brake attachment design. Those dropouts
certainly could have had more substantial Lawyer Lips and the angle for the
dropout was exactly wrong.
I think it will be interesting to find out what the bicycle industry has to say
about this, whether they have really done the engineering required as I
orginally believed they had done or if they dropped the ball and let something
slip through.
I will say that I was unpleasently surprised to see the dropout design on that
Novara.
Jon Isaacs
James Annan
>
> Time will tell whether I am a lame brain or you are Chicken Little.
I make no strong claims about the magnitude of the problem, I'm only
explaining what goes wrong when it does. I know is it quite rare in
absolute terms, but it can have extremely serious consequences. I'm not
sure how you get from there to Chicken Little.
James
James Annan
> I think it will be interesting to find out what the bicycle industry has to say
> about this, whether they have really done the engineering required as I
> orginally believed they had done or if they dropped the ball and let something
> slip through.
Pace's open letter gives one manufacturer's opinion.
James
Jose Rizal
However, bear in mind that the larger the rotor diameter, the greater
the load on the fork brake mounts. This is the reason that suspension
fork manufacturers (eg Manitou, Fox) void the warranty on their
"standard" (ie non-downhill) forks if larger than 6" rotors are used.
Terry Morse
> However, bear in mind that the larger the rotor diameter, the greater
> the load on the fork brake mounts. This is the reason that suspension
> fork manufacturers (eg Manitou, Fox) void the warranty on their
> "standard" (ie non-downhill) forks if larger than 6" rotors are used.
Please explain. For a given braking force, a larger diameter rotor will
lessen--not increase--the force on the brake mounts. There must be some
other reason why fork manufacturers don't want large diameter rotors.
--
terry morse Palo Alto, CA http://www.terrymorse.com/bike/
Doug Taylor
By the same token, I don't see how you get to I'm "stupid" because I'm
not getting a big hard on worrying about my wheel (with snugly
fastened QR and lawyer lips on fork dropout) falling off.
--dt
Jose Rizal
> Jose Rizal wrote:
>
> > However, bear in mind that the larger the rotor diameter, the greater
> > the load on the fork brake mounts. This is the reason that suspension
> > fork manufacturers (eg Manitou, Fox) void the warranty on their
> > "standard" (ie non-downhill) forks if larger than 6" rotors are used.
>
> Please explain. For a given braking force, a larger diameter rotor will
> lessen--not increase--the force on the brake mounts. There must be some
> other reason why fork manufacturers don't want large diameter rotors.
A larger rotor will decrease the force required by the calipers to
supply the same moment about the axle as a smaller rotor, but the
bending moment on the fork mounts, which now see a larger moment arm
despite the decreased force on the caliper, is increased.
Quoted from a post I made some time ago on the subject:
"Consider a free body diagram of a fork and disc brake system, and
assume that the caliper mounting posts are parallel to the radial line
from the axle to the center of the caliper contact area.
This does not affect the validity of the analysis since the mounting
posts can be looked upon as moment arms. Also assume that the caliper
center is exactly between the tips of the mounting posts.
Now in the case of a small rotor with diameter Ro, the force exerted by
the caliper Fo is taken up by the two mounting posts. Assume that each
post takes up exactly half the caliper force, or 0.5*Fo. The moment
about the base of each post will then be
1) 0.5 * Fo * Lo,
where Lo is the length of the mounting post.
Now consider the case of a larger rotor, say R1. Assume that the
mounting posts are lengthened by the same amount as the increase in
radius for the larger rotor, that is,
2) R1 - Ro = L1 - Lo
and the posts are still parallel to the axle-caliper radial line.
Since the moment about the axle needs to be the same as with the smaller
rotor, then
3) F1 * R1 = Fo * Ro.
and so
4) F1 = Fo * Ro/R1.
The moment about the base of each post will now be
5) Moment = 0.5 * F1 * L1 = 0.5 * Fo * Ro/R1 * L1
But L1 = (R1 - Ro + Lo) from 2) above, so the moment on each post is
6) Moment = 0.5 * Fo * Ro/R1 * (R1 - Ro + Lo).
Plugging in typical numbers show clearly that the larger the disc brake
rotor, the greater the moment exerted on the fork leg brake mounts."
Example: let Ro = 76.2mm (6" rotor), Lo = 15mm, and R1 = 101.6mm (8"
rotor)
Plug into 1) and 6) above and it's clear that the moment on each
mounting post is about 2 times greater for the larger rotor than for the
smaller rotor.
Stergios Papadakis
>
> What makes you think they are not thinking about it?
>
> One thing to realize is the website in question was the result of a crash
> involving a bike with no retaining lips. It took a good deal of effort to get
> the site owner to be upfront about this.
>
> Jon Isaacs
I think this is a bad argument. The system should NOT
rely on the retaining lips to keep the axle in position.
Every fork's dropout shape will be slightly different, and
QRs vary in their exact geometry.
If the system is to rely on the lips to keep the axle
in position, then the outer diameter of the face of the
QR would have to exactly press against the tops of the
retaining lips when the axle was fully in the dropouts
(obviously, since the fork makers don't also supply the
axle and QR, they aren't designing them this way).
Otherwise, the axle could shift until the QR bears against
the lips. That is not something you want.
Perhaps a particular crash would have been prevented by using a fork
with lips. That doesn't mean the QR + disk brake system
is an OK design. You shouldn't have to reposition your
front wheel QR unless you want to.
Stergios
GigaNews
with disc brakes, had a QR become loose.
I understand the force diagram, but fail to see what would cause the QR to
loosen, unless it was already extremely loose to begin with and vibrated
out. My QRs all have serrated faces so this is essentially a non-problem.
I think a simple force balance will also tell you that the force pushing the
wheel out of the dropout is dramatically smaller than the force required to
move the wheel if the skewer is tightened properly or even anywhere near
properly.
you = Chicken little.
"James Annan" <still_th...@hotmail.com> wrote in message
news:3EC2213...@hotmail.com...
Mike S.
"GigaNews" <Nob...@nowhere.com> wrote in message
news:YHqdnSZUs6t...@giganews.com...
> I have never, in several years and many thousands of miles of hard riding
> with disc brakes, had a QR become loose.
>
> I understand the force diagram, but fail to see what would cause the QR to
> loosen, unless it was already extremely loose to begin with and vibrated
> out. My QRs all have serrated faces so this is essentially a non-problem.
>
> I think a simple force balance will also tell you that the force pushing
the
> wheel out of the dropout is dramatically smaller than the force required
to
> move the wheel if the skewer is tightened properly or even anywhere near
> properly.
>
> you = Chicken little.
>
is that discs and QRs shouldn't mix, and the other says: properly used the
QR should be fine.
If discs and QRs are a bad combo, why is it that there are only a very, very
small minority of riders ever having problems with the combo? I know in my
experience with QRs and discs, that I haven't noticed anything different
than if I was running rim brakes.
Which led me to thinking about forces on the rear of the bike. Shouldn't
the force of pedaling the bike do the same thing to the rear wheel as discs
do to the front? Since most mtn dropouts are semi- to vertical, shouldn't
the force of pedaling try to pull the rear wheel out of the dropout too?
What about discs in the rear?
So, if the rear dropouts are OK, why aren't the fronts?
I'm still not convinced its not a case of "user error." I detect hints of
the Audi "unintended acceleration" syndrome here. As y'all know, I'm NOT an
engineer, just curious.
Mike
James Annan
> I think a simple force balance will also tell you that the force pushing the
> wheel out of the dropout is dramatically smaller than the force required to
> move the wheel if the skewer is tightened properly or even anywhere near
> properly.
I think the simple force balance calculation on my web pag contradicts
your belief. I think if you were capable of understanding it, you
wouldn't have posted your comment.
James
Andreas Oehler
>
>> However, bear in mind that the larger the rotor diameter, the greater
>> the load on the fork brake mounts. This is the reason that suspension
>> fork manufacturers (eg Manitou, Fox) void the warranty on their
>> "standard" (ie non-downhill) forks if larger than 6" rotors are used.
>
>Please explain. For a given braking force, a larger diameter rotor will
>lessen--not increase--the force on the brake mounts. There must be some
>other reason why fork manufacturers don't want large diameter rotors.
The only reasons I know against the use of bigger-than-usual discs is that
areas in the fork leg are heated which do not like the heat or that the
bigger disc will touch the fork leg.
Andreas (Magura Julie at the tandem on a steal fork)
Jose Rizal
No, it's everything to do with the increased bending moment on the base
of the fork brake mounts when using larger rotors. This is what Manitou
says; see the calculations on my previous post.
W K
From the "math" it seems clear that the QR is only just holding the front
wheel in in these circumstances.
At the very least you are going to have to stop calling those lumps of metal
"lawyer lips".
Its your secondary parachute, and how many people would sky-dive if they
knew that under fairly standard conditions they were actually relying on the
seldom used secondary safety device.
Jose Rizal
I could not see anything on your website which quantitatively compares
the force trying to move the axle off the dropout to the force required
to move a "tight" quick release mechanism. If you can show on a graph
the force required to move a QR for a given braking rate, vs the
"tightness" with which the QR is done up, you will be able to have a
proper comparison of the forces involved. The easiest way to determine
this is by empirical means.
W K
"Mike S." <mikeshaw2@coxDOTnet> wrote in message
news:GARwa.32722$eJ2.28@fed1read07...
> I've been wondering about this thread. Seems that there are two camps:
one
> is that discs and QRs shouldn't mix, and the other says: properly used the
> QR should be fine.
Naah.
Third camp: this works but looks bad.
So, we need some sensible discussion about whether it is a problem.
I'm sure J.A. is not far off this point, as he is a scientist who would be
convinced by decent evidence countering his point.
Please note that one of our usenet colleages has fractured his spine
irrepairably recently when the front wheel came out of his downhill bike.
M-Gineering import & framebouw
>
> No, it's everything to do with the increased bending moment on the base
> of the fork brake mounts when using larger rotors. This is what Manitou
> says; see the calculations on my previous post.
V brakes run a pretty big Rotor and didn't fall off much!
--
Marten
Jose Rizal
The glaringly obvious difference is that V-brake mounts are very close
to the pads. Hence, moments about the V-brake mounts are much smaller.
Imagine that the V-brake mounts are actually located half an inch away
from the axle, rather than half an inch away from the pads, and you
might get an insight into the difference between the two cases.
jobst....@stanfordalumni.org
>> I understand the force diagram, but fail to see what would cause
>> the QR to loosen, unless it was already extremely loose to begin
>> with and vibrated out. My QRs all have serrated faces so this is
>> essentially a non-problem.
This was discussed at length the first time this subject came under
discussion. Recognizing that the disengagement force in the axle is
great enough to separate it from the dropout in the absence of
retention lips, even with properly closed QR, it should be apparent
that the QR nut will move to its downward limit in the retention lips.
Subsequently, on the next road shock, it will move back to its upper
"normal" position. Repeating this motion, although small, will unscrew
the QR, especially if the closure lever is at the opposite side from
the disc brake.
>> I think a simple force balance will also tell you that the force
>> pushing the wheel out of the dropout is dramatically smaller than
>> the force required to move the wheel if the skewer is tightened
>> properly or even anywhere near properly. you = Chicken little.
> I've been wondering about this thread. Seems that there are two
> camps: one is that discs and QRs shouldn't mix, and the other says:
> properly used the QR should be fine.
> If discs and QRs are a bad combo, why is it that there are only a
> very, very small minority of riders ever having problems with the
> combo? I know in my experience with QRs and discs, that I haven't
> noticed anything different than if I was running rim brakes.
If the wheel is removed after each ride, to put the bicycle in a car
for instance, QR loosening will not be noticed and will be corrected
when the wheel is again installed. If however, if the bicycle is not
disassembled and ridden continuously, incremental loosening will grow.
Since MTB's are nearly all transported to the scene of the crime, they
have no problem and believe there is no problem.
> Which led me to thinking about forces on the rear of the bike.
> Shouldn't the force of pedaling the bike do the same thing to the
> rear wheel as discs do to the front? Since most MTB dropouts are
> semi- to vertical, shouldn't the force of pedaling try to pull the
> rear wheel out of the dropout too? What about discs in the rear?
The rear dropout is always loaded in the same direction, both by chain
tension and brake disc. Maybe if you dig in the RBR-Tech archive you
can review all this.
> So, if the rear dropouts are OK, why aren't the fronts?
Apparently you don't understand the force diagram. It depends on the
location of the brake caliper.
> I'm still not convinced its not a case of "user error." I detect
> hints of the Audi "unintended acceleration" syndrome here. As y'all
> know, I'm NOT an engineer, just curious.
There is no parallel to someone stepping on the gas instead of the
brake in the bicycle disc brake problem.
amerigo
"Dave Kahn" <dkah...@yahoo.co.uk> ha scritto nel messaggio
news:57db8bde.03051...@posting.google.com...> (Quoting from http://www.bikebiz.co.uk/web/article.php?id=2899 )
>
> > If the QR problem is ignored, could the bike trade be crippled by
> > similar lawsuits?
>
>
> --
> Dave...
I think that the danger is much bigger for the front brake, because the
position of the rear brake is different, so the force generated by the brake
is not directed vertically,but it is - almost - horizontal, how much
horizontal it is, it depends from the position of the brake: if it is
vertically above the hub, the force will be horizontal, if it is not, the
resultant force will try to move down the hub
http://www.rothar.com/160303.htm
From: James
Subject: Disc brakes and QRs
Yes, and I'm in the same position as you. I don't think it's a big safety
issue, but in my case it is a slightly annoying one. It depends on how the
dropouts are angled relative to the disk calliper, and my bike (Ventana El
Conquistador tandem) is particularly bad, with rearward facing dropouts
which are at exactly the worst possible angle for the disc brake. The maker
soon realised the error and changed to more conventional vertical ones. If
only major fork manufacturers were so responsive.... That is another reason
why I am particularly aware of the disk brake issue - our rear wheel
occasionally slips a bit although now I do the QR up bloody tight and it's
been ok for some time. It's similar to QRs with horizontal dropouts for
singlespeeding - you can just about get away with it, but slippage is a
headache (rear wheel slip while honking up a big hill is not a matter of
life and death though).
I wouldn't trust my life to the rear wheel not slipping, but its not a big
safety issue in my view since even if the rear wheel slips sideways a bit or
pulls out completely, this is only going to cause a skid and not a headfirst
plummet to the ground (especially on a tandem with the long stable
wheelbase). I don't think different disk calliper types will make a
significant difference, it's really just a matter of geometry. The open fork
ends should point directly away from the calliper itself, rather than being
nearly parallel to the tangent.
Mark Lee
"Jose Rizal" <_@_._> wrote in message
news:%cTwa.72498$ey1.6...@newsread1.prod.itd.earthlink.net...
amerigo
"Stergios Papadakis" <papa...@physics.unc.edu> ha scritto nel messaggio
news:3EC3C7E1...@physics.unc.edu...
> Jon Isaacs wrote:
> >
> > What makes you think they are not thinking about it?
> >
> > One thing to realize is the website in question was the result of a
crash
> > involving a bike with no retaining lips. It took a good deal of effort
to get
> > the site owner to be upfront about this.
> >
> > Jon Isaacs
>
> I think this is a bad argument. The system should NOT
> rely on the retaining lips to keep the axle in position.
you are saying the right thing. The qr will still open and come loose also
if there are the retaining lips!!!! You will probably not loose the wheel,
but if you don't recognize soon that the qr has opened itself, you will
loose the wheel anyway
S. Anderson
> statistics which prove there is a cost benefit to re-engineering the
> system , I remain unconcerned and unconvinced. I certainly have no
> plans to change the components on my mountain bike as it is currently
> set up, or stop using it.
>
> Time will tell whether I am a lame brain or you are Chicken Little.
> --dt
And that's really what it will boil down to. How much to change the system
in place versus how much to pay off the liability claims. I've looked at
Mr. Annan's analysis and although there is some supposition with respect to
the magnitudes of certain forces, it's impossible to ignore the basic design
flaw. There will be discussion about potential corrections, their impact on
basic concept of a QR wheel, costs, costs of liablity etc. and something MAY
be changed at some point in the future. There are certainly existing
systems that will adequately keep the wheel in place (just look at any of
the through-axle forks on DH bikes). A knife is sharp and will cut your
hand if you slip while cutting something, but it IS a knife. You trade off
convenience for safety. Maybe the incidence of failure is so insignificant
that people and companies will accept the risks involved to be able to drop
their wheel out in 2 seconds instead of 10. As you say, time will tell.
But to deny the problem is faulty.
Cheers,
Scott..
James Annan
> James Annan:
>
>>
>>I think the simple force balance calculation on my web pag contradicts
>>your belief. I think if you were capable of understanding it, you
>>wouldn't have posted your comment.
>>
>>James
>
>
> I could not see anything on your website which quantitatively compares
> the force trying to move the axle off the dropout to the force required
> to move a "tight" quick release mechanism. If you can show on a graph
> the force required to move a QR for a given braking rate, vs the
> "tightness" with which the QR is done up, you will be able to have a
> proper comparison of the forces involved. The easiest way to determine
> this is by empirical means.
Ok, it's true that I did not actually quote directly from the QR test
results, but I did provide a link to the PDF and a few words of summary.
To save you the trouble of downloading it, the QRs did achieve the min
ISO pull resistance of 1150N each side (2300N symmetrical), but the
maximum that any of them achieved was about the level of the force
described on my page. Several were actually destroyed in the test due to
the torque applied to close and open the lever.
James
Mike S.
<jobst....@stanfordalumni.org> wrote in message
news:_RTwa.14499$JX2.8...@typhoon.sonic.net...
Mike
Chris Zacho The Wheelman
that wants to push the axle out of the dropout by a ratio of wheel
diameter to disk diameter (if the caliper is behind the fork).
That translates to the smaller the disc the greater the disengaging
force. I see no physics astute contributors disagreeing with James's
assessment of the problem, only disbelievers who show no reason why it
is not so, other than they haven't crashed yet.
Jobst Brandt
jobst....@stanfordalumni.org
Palo Alto CA "
Which brings up the question, how does fork rake factor into the
equation? I have standard, non-suspension "raked" forks.
May you have the wind at your back.
And a really low gear for the hills!
Chris
Chris'Z Corner
"The Website for the Common Bicyclist":
http://www.geocities.com/czcorner
Chris Zacho The Wheelman
"My personal opinion is that with a well designed Lawyer Lip, this
should not be a problem. Another solution is to simply place the brake
ahead of the fork, this way the moment pushes the wheel into the fork
rather than away from it."
Wouldn't an easier solution be to simply change the dropout angle? So
that the wheel slides out in a down and forward direction rather than a
down and out direction?
Occam's Razor
(Pete Cresswell)
>I think that the danger is much bigger for the front brake, because the
>position of the rear brake is different,
Not to mention that if you lose the rear wheel, you'll still have some semblance
of balance/control - whereas if you lose the front wheel you're going to bite
the big one big-time...
-----------------------
PeteCresswell
Tim McNamara
"Mike S." <mikeshaw2@coxDOTnet> wrote:
> No, but there's lots of hysteria about this too.
There's been no hysteria. There's been a presentation by James Annan,
backed up by his engineering analysis, and examined by other
mechanical engineers who agree with him. The bike industry has been
made aware of this issue and is considering it- and considering their
response. Annan has done the industry and bike riders a service by
bringing up this issue.
There's been disagreement- initially from myself, as a matter of fact,
as well as others; but after careful consideration and having a few
questions answered by James and Jobst, I find myself in agreement. I
had been parroting the myth and lore that front wheels don't fall off
bikes if the QR is used properly- which is true *except* with current
disk brake designs. QRs were not designed with disk brakes in mind.
There are basically two factors, as far as I can tell.
First, the placement of the brake caliper behind the fork results in a
force vector that can eject the wheel from the dropout. I would
imagine this could be readily demonstrated by laying the bike upside
down, loosening the QR, spinning the wheel in the correct direction
and applying the brake. The axle should pop right out of the dropout.
The faster the wheel spins, the greater the ejection force. Note that
I haven't tried, this, not having a bike with disk brakes. Somebody
give it a try and let us know how it turns out.
Second, the cyclic application of this ejection force nudges the axle
away from the top of the dropout slot when riding, each time the brake
is applied hard. Normal riding knocks the axle back to the top of the
slot. Repeat time and time again. This bends and flexes the axle and
QR, eventually causing the QR nut to begin to loosen. It can
eventually loosen enough to allow the axle to be forced out of the
dropout.
As far as I can tell, simply locating the caliper in front of the fork
would eliminate this problem. Or even moving it around the rotor so
the resultant force isn't in line with the dropout might help; surfing
around on motorcyle Web sites suggests that those manufacturers have
already sussed this issue- their placement of calipers tends to be at
the top of the rotor (e.g., see the Harley Web site), analogous to the
placement of rim brakes, as a matter of fact.
Joshua Putnam
Chrisz...@webtv.net (Chris Zacho "The Wheelman") says...
> Jon Issacs wrote:
>
> "My personal opinion is that with a well designed Lawyer Lip, this
> should not be a problem. Another solution is to simply place the brake
> ahead of the fork, this way the moment pushes the wheel into the fork
> rather than away from it."
>
> Wouldn't an easier solution be to simply change the dropout angle? So
> that the wheel slides out in a down and forward direction rather than a
> down and out direction?
Since most high-performance bikes over the past half century have been
using really big disks (the rim) with the brake ahead of the fork,
wouldn't it be simpler to put the brake ahead of the fork when using
small disks, too? That allows continued compatibility with the millions
of bikes that came along before the popularity of small disks.
--
jo...@phred.org is Joshua Putnam
<http://www.phred.org/~josh/>
Braze your own bicycle frames. See
<http://www.phred.org/~josh/build/build.html>
Doug Taylor
news:YYTwa.4831$I83.7...@news20.bellglobal.com...
> But to deny the problem is faulty.
For the record, I reiterate that I do not deny the problem. I merely
suggest that the "problem" appears to be one of such low risk that I am not
personally concerned and have no plans to trash my existing equipment or to
stop riding my mt. bike. I will, however, take pains to verify that my QR
is soundly fastened before each ride, given the mathematical possibilty (not
probability) of failure.
stu
of the dropout, its thickness and the length of axle in the dropout.
On my bike the tyre is rubbing against the fork long before the axle clears
the dropout, but if the dropouts were shorter or the axle wasn't as far
through the dropout then the axle could fall out before the tyre hit the
fork(so tyre and fork width have something to do with it to).
l don't have discs so l don't know how hard then disc has to push against
the calliper to let the axle clear the dropout.
l think you have to have allot of things working against you before there is
a problem, but its a hell of a problem if it happens. So if l ever get
around to discs l want them in front of the fork(l think it would be much
nicer to have a torque triangle with 3 sides, than a torque triangle with 2
sides)
at least l think its a torque triangle????lol
James Annan
Thanks for the neat summary.
> There's been disagreement- initially from myself, as a matter of fact,
> as well as others; but after careful consideration and having a few
> questions answered by James and Jobst, I find myself in agreement.
I have absolutely no objection to, and indeed welcom, a bit of
intelligent scepticism: it was only due to the (correct) insistence of
people like yourself, Jon Isaacs and others that a tight QR simply
cannot pull directly over a lip, that I eventually got round to the
conclusion that the QR loosened first. And without that final detail,
I'd have just been one more crank to be dismissed along with the new
revolutionary pedal drive and automatic gear changing.
It is, however, getting a bit tedious seeing the same trivial points
over and over again from bloke-on-a-bike types who imagine that their
off-the-cuff opinion is going to unravel several weeks worth of careful
analysis and inspection by a range of experts. That criticism certainly
doesn't apply to all the comments posted here, but it describes most of
my mailbox!
James
Doug Taylor
>I have absolutely no objection to, and indeed welcom, a bit of
>intelligent scepticism: it was only due to the (correct) insistence of
>people like yourself, Jon Isaacs and others that a tight QR simply
>cannot pull directly over a lip, that I eventually got round to the
>conclusion that the QR loosened first. And without that final detail,
>I'd have just been one more crank to be dismissed along with the new
>revolutionary pedal drive and automatic gear changing.
>
>It is, however, getting a bit tedious seeing the same trivial points
>over and over again from bloke-on-a-bike types who imagine that their
>off-the-cuff opinion is going to unravel several weeks worth of careful
>analysis and inspection by a range of experts. That criticism certainly
>doesn't apply to all the comments posted here, but it describes most of
>my mailbox!
As a "bloke [or "dude'" on USA side of the pond)-on-a-bike type who
has ridden thousands and thousands of miles off-road with disc brakes
without a QR release, knows hundreds of people who have ridden many
more thousands and thousands of miles with disc brakes without a QR
release, here is what I glean as an ignorant and stupid layman from
the conclusions of Annan and Brandt:
If you ride some unspecified but significantly large amount of miles
with disc brakes, the QR eventually will loosen to a degree that it
could pop over the dropout tabs and the wheel will fall off.
My own empirical experience (which must be discounted or ignored
since it is merely one sample, and only of a bloke-on-a-bike) is that
this period must be large indeed, as I have competed in three 24 Hour
races, with 6-7 hours of personal continuous riding, without touching
the QR and no mishap.
As Brandt admits, the majority of off-road bikes are transported with
front wheel removed, so that it is reinstalled often before a ride.
Most off-road rides last significantly less than 6 hours (try 1, 2 or
3 hours), when the wheel will be removed again.
Solution to the "problem": adjust the QR before you ride your bike
(or every 3 or 4 hours or so ). The odds are utterly overwhelming
that you will NEVER have QR loosen to the point of your wheel falling
off.
--dt
Mark Hickey
>This was discussed at length the first time this subject came under
>discussion. Recognizing that the disengagement force in the axle is
>great enough to separate it from the dropout in the absence of
>retention lips, even with properly closed QR, it should be apparent
>that the QR nut will move to its downward limit in the retention lips.
>Subsequently, on the next road shock, it will move back to its upper
>"normal" position. Repeating this motion, although small, will unscrew
>the QR, especially if the closure lever is at the opposite side from
>the disc brake.
It seems to me that the effect of a properly-closed QR moving up and
down in the dropout will be obvious. On my own MTB (non-disc BTW),
the QR engagement zone is an obvious clean circle, with no signs of
movement of the QR's faces while riding.
However, I'm sure there are a lot of folks out there reading this
discussion who have a front disc brake. How many of them see signs of
"QR wandering" on their dropouts? It should be very obvious, since
the initial movement occurs with the QR fully closed and tight (which
should leave obvious "trail of damage" across the faces of the
dropout.
It would be interesting to do a quick poll of riders at a race to see
how many have dropouts showing signs of QR movement.
Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $695 ti frame
GigaNews
I am more than capable of understanding the calculations on your website.
Any first-year engineering student can understand them. I would expect
better quality diagrams from most first-year engineering students, however.
Do not be too impressed with yourself. You have not proved Fermat's Last
Theorem, or even performed a particularly thorough analysis. You are
presenting as 'results' some calculations which no technical journal on
earth would publish. They would be sent back to you asking that you either
change your tone to properly present this as a topic worthy of research or
perform some actual testing to back up your claims.
Until you perform proper testing I will remain skeptical. At this point all
you are doing is screaming that the sky is falling. You sound like Ralph
Nader, for Pete's sake, and you are oblivious to the danger that you will
force changes in an area that you have not properly shown to be a difficulty
(indeed there is a great deal of anecdotal evidence indicating otherwise)
simply because manufacturers will be scared of lawyers. A proper scientist
would have a more rational approach.
Until someone applies a real scientific approach to this problem, I will
continue to ride without one shred of fear that my front wheel which has
been happily staying in place for many thousands of miles of hard riding
will fail to do so.
Bill
"James Annan" <still_th...@hotmail.com> wrote in message
news:3EC3F484...@hotmail.com...
Jon Isaacs
>backed up by his engineering analysis, and examined by other
>mechanical engineers who agree with him. The bike industry has been
>made aware of this issue and is considering it- and considering their
>response. Annan has done the industry and bike riders a service by
>bringing up this issue.
I agree with you, he has done the industry a service and I hope they take note.
>
>There's been disagreement- initially from myself, as a matter of fact,
>as well as others; but after careful consideration and having a few
>questions answered by James and Jobst, I find myself in agreement.
I know I was certainly vocal and adament about James providing information and
being clear on several issues, including stating upfront that the fork on his
bike lacked any lawyer lips.
At this point, I think he has done his homework and gathered a sufficient
amount of anecdotal data that indicates this is indeed a real issue.
>I had been parroting the myth and lore that front wheels don't fall off
>bikes if the QR is used properly- which is true *except* with current
>disk brake designs. QRs were not designed with disk brakes in mind.
>There are basically two factors, as far as I can tell.
>
>First, the placement of the brake caliper behind the fork results in a
>force vector that can eject the wheel from the dropout. I would
>imagine this could be readily demonstrated by laying the bike upside
>down, loosening the QR, spinning the wheel in the correct direction
>and applying the brake. The axle should pop right out of the dropout.
>The faster the wheel spins, the greater the ejection force. Note that
>I haven't tried, this, not having a bike with disk brakes. Somebody
>give it a try and let us know how it turns out.
>
>Second, the cyclic application of this ejection force nudges the axle
>away from the top of the dropout slot when riding, each time the brake
>is applied hard. Normal riding knocks the axle back to the top of the
>slot. Repeat time and time again. This bends and flexes the axle and
>QR, eventually causing the QR nut to begin to loosen. It can
>eventually loosen enough to allow the axle to be forced out of the
>dropout.
>
>As far as I can tell, simply locating the caliper in front of the fork
>would eliminate this problem.
That was the same suggestion I had made, I am still not quite sure why the
calipers are to the rear, supposedly this has to with reducing the inertia of
the fork but I wonder how important really is.
Or even moving it around the rotor so
>the resultant force isn't in line with the dropout might help;
I think Jame's suggestion is to change the dropout design so that it is not
inline with the force which is also a reasonable solution.
Stepping back from this issue a ways and taking a look at the big picture, I
think QRs do seem to work and they seem to work quite well as they have been
used traditionally.
But I can think of no other application I have ever seen that merely depends on
friction to secure a component as critical as the front wheel of a bicycle.
Wheels are bolted in place, SOP.
Jon Isaacs
Jon Isaacs
>(or every 3 or 4 hours or so ). The odds are utterly overwhelming
>that you will NEVER have QR loosen to the point of your wheel falling
>off.
A front wheel falling off is a catatrophic event. The current design is flawed
and while the failures may be few and far between, it is still a flawed design.
There are several simple ways to take care of these flaws and their
consequences are minimal or non-existent.
Imagine that someday you or some friend of yours is riding down the road and
the front wheel falls off when the brakes are applied.
Now imagine someone points out that with a simple no-cost change in the design,
that would not have happened.
Then imagine what you would think.
Jon Isaacs
Jon Isaacs
>position of the rear brake is different
Also the braking forces possible with the rear wheel are much reduced.
jon isaacs
Jon Isaacs
>the way? I remember you being rather sceptical at first, but as soon as
>I suggested that the QR could unscrew you seemed to go very quiet.
>
>James
I think you have addressed an interesting problem and done a nice job with it.
I support what you have done. Previously you commented that my pressing you
on certain issues had been helpful and and I am glad that you have gained
further understandings.
As I have said elsewhere in this thread, I think in many forks the retention
method, including the Lawyer Lips are flawed.
So I commend you on your efforts, you have convinced me.
jon isaacs
Doug Taylor
>>Solution to the "problem": adjust the QR before you ride your bike
>>(or every 3 or 4 hours or so ). The odds are utterly overwhelming
>>that you will NEVER have QR loosen to the point of your wheel falling
>>off.
>A front wheel falling off is a catatrophic event.
So is a front tire flat. Care to speculate which odds are greater: a
front wheel flat on a road bike or a wheel falling off a mtn bike due
to a QR unscrewing after using a disc brake? Impossible to know, but
I would stick my neck way out and guess that the former is far more
common, if only because I happen to know two people it actually
happened to (again, a completely unscientific sampling). I've ridden
a mtn bike with disc brakes for 3 years now, and with people who have
used them for 5, and before Annan never even imagined such a thing as
a wheel coming off, let alone knowing of it actually happening.
Both people who flatted in front crashed bad, and no need to get into
it. Did they or I quit cycling because of it? No. The odds are
still minuscule. Getting hit by a car is a far, far more likely, and
equally as or more threatening to life and limb. Going over the bars
on a mtn. due to an obstacle is far, far more likely than the wheel
falling off.
Yet we still ride our bikes.
> The current design is flawed
>and while the failures may be few and far between, it is still a flawed design.
This I don't dispute.
>There are several simple ways to take care of these flaws and their
>consequences are minimal or non-existent.
Other than simply adjusting the QR before you ride? Such as?
>Imagine that someday you or some friend of yours is riding down the road and
>the front wheel falls off when the brakes are applied.
>
>Now imagine someone points out that with a simple no-cost change in the design,
>that would not have happened.
>
>Then imagine what you would think.
If indeed the fix is simple and no cost, no one would possibly argue
with you. Bring it on; I'll take it.
But please elaborate. Right now I have expensive forks and disc
brakes. To replace them would cost well over a $500 (no need to get
into that either). Sorry, but the cost exceeds the benefit. I don't
need to replace them immediately; I can be vigilant that my QR is snug
before I ride and be utterly safe and care free (other than of the
REAL risks of the sport.) When I replace them in due course, and if
the industry has redesigned and improved the system, I will certainly
by the state of the art.
--dt
jobst....@stanfordalumni.org
> It is, however, getting a bit tedious seeing the same trivial points
> over and over again from bloke-on-a-bike types who imagine that
> their off-the-cuff opinion is going to unravel several weeks worth
> of careful analysis and inspection by a range of experts. That
> criticism certainly doesn't apply to all the comments posted here,
> but it describes most of my mailbox!
Not to worry. This is typical of the bicycle industry and its
faithful. It took 15 years for the concepts presented in "the Bicycle
Wheel" to be generally acknowledged and accepted. Until a couple of
years ago, insulting attacks were common fare here on wreck.bike. The
greater audience and the industry are slow to grasp new concepts but
time wounds all heels.
Indexed steering, crank failures, crank spindle failures, pedal
attachment, fretting of closely fitting parts, sealed bearings...
These are all well discussed subjects here but are only gradually
being recognized.
Patience!
jobst....@stanfordalumni.org
>> A front wheel falling off is a catastrophic event.
> So is a front tire flat. Care to speculate which odds are greater:
> a front wheel flat on a road bike or a wheel falling off a mtn bike
> due to a QR unscrewing after using a disc brake? Impossible to
> know, but I would stick my neck way out and guess that the former is
> far more common, if only because I happen to know two people it
> actually happened to (again, a completely unscientific sampling).
> I've ridden a mtn bike with disc brakes for 3 years now, and with
> people who have used them for 5, and before Annan never even
> imagined such a thing as a wheel coming off, let alone knowing of it
> actually happening.
From this I take it you have never had a front tire go flat or for
that matter have a blowout. Of course these are relatively common
events and a blowout can be catastrophic if it occurs at a critical
moment. However, a wheel separation is a catastrophic event at any
speed over 10mph or so. It produces the end-over that was the bane of
penny-farthings.
> Both people who flatted in front crashed bad, and no need to get into
> it. Did they or I quit cycling because of it? No. The odds are
> still minuscule. Getting hit by a car is a far, far more likely, and
> equally as or more threatening to life and limb. Going over the bars
> on a mtn. due to an obstacle is far, far more likely than the wheel
> falling off.
You are trying to compare avoidable failures with unavoidable ones.
Although riders regularly descend mountain roads at high speed and
approach hairpin turns, that if missed, are fatal, and yet there are
no reports of bicyclist fatalities from flats. A wheel separation
from a disc brake occurs only while braking hard and it will cause the
rider to take a headlong dive. This is a serious matter and not
entirely under the control of the user. How this can occur has been
amply presented.
Gary Young
<snip>
> As a "bloke [or "dude'" on USA side of the pond)-on-a-bike type who
> has ridden thousands and thousands of miles off-road with disc brakes
> without a QR release, knows hundreds of people who have ridden many
> more thousands and thousands of miles with disc brakes without a QR
> release, here is what I glean as an ignorant and stupid layman from
> the conclusions of Annan and Brandt:
>
> If you ride some unspecified but significantly large amount of miles
> with disc brakes, the QR eventually will loosen to a degree that it
> could pop over the dropout tabs and the wheel will fall off.
>
> My own empirical experience (which must be discounted or ignored
> since it is merely one sample, and only of a bloke-on-a-bike) is that
> this period must be large indeed, as I have competed in three 24 Hour
> races, with 6-7 hours of personal continuous riding, without touching
> the QR and no mishap.
Hell, my grandpappy smoked two packs a day, and he lived to be 100! I
don't know what all this nonsense about smoking is.
You so accurately diagnose the shortcomings of your reasoning one
wonders why you bothered to post this message at all. Is ignorance a
point of pride with you?
> As Brandt admits, the majority of off-road bikes are transported with
> front wheel removed, so that it is reinstalled often before a ride.
> Most off-road rides last significantly less than 6 hours (try 1, 2 or
> 3 hours), when the wheel will be removed again.
>
Perhaps, but there are probably thousands of riders who don't remove
their front wheel very often. That may be a minority, but it's a
significant minority.
>
> Solution to the "problem": adjust the QR before you ride your bike
> (or every 3 or 4 hours or so ). The odds are utterly overwhelming
> that you will NEVER have QR loosen to the point of your wheel falling
> off.
What a wonderful solution! Too bad about the millions of riders who
don't read rec.bicycles.tech and won't know there's even a danger.
Given the fact that the consequences of this type of failure can be
quite severe, what is your problem with encouraging manufacturers to
fix it?
amerigo
"GigaNews" <Nob...@nowhere.com> ha scritto nel messaggio
news:65udnWIz9Jo...@giganews.com...
>
> I am more than capable of understanding the calculations on your website.
> Any first-year engineering student can understand them. I would expect
no one did it before, you are jealous of his idea
> better quality diagrams from most first-year engineering students,
however.
> Do not be too impressed with yourself. You have not proved Fermat's Last
> Theorem, or even performed a particularly thorough analysis. You are
> presenting as 'results' some calculations which no technical journal on
> earth would publish. They would be sent back to you asking that you either
> change your tone to properly present this as a topic worthy of research or
> perform some actual testing to back up your claims.
specialized, trek, cannondale and all those morons must make the tests
>
> Until you perform proper testing I will remain skeptical. At this point
all
> you are doing is screaming that the sky is falling.
you will fall
You sound like Ralph
> Nader, for Pete's sake, and you are oblivious to the danger that you will
> force changes in an area that you have not properly shown to be a
difficulty
> (indeed there is a great deal of anecdotal evidence indicating otherwise)
> simply because manufacturers will be scared of lawyers. A proper scientist
> would have a more rational approach.
>
> Until someone applies a real scientific approach to this problem, I will
> continue to ride without one shred of fear that my front wheel which has
> been happily staying in place for many thousands of miles of hard riding
> will fail to do so.
ah ah
Doug Taylor
>Given the fact that the consequences of this type of failure can be
>quite severe, what is your problem with encouraging manufacturers to
>fix it?
Absolutely none. Did you pay attention to the entire thread? Do you
have reading comprehension problems?
My point was and is that the minuscule theoretical chance that my
front wheel "could" fall off due to QR failure does NOT impel me
immediately to stop riding my mt. bike as it currently is equipped, or
to buy new equipment. The cost is inversely proportional to the
benefit. My QR can be and is adjusted with enough frequency to avoid
the predicted (by rarely encountered in fact) result.
Anyone who is so frightened by Annan's theory that he or she locks his
current bike in the basement waiting for the cure is overreacting in
the extreme.
If and when: 1) the theory is proven to be correct; 2) alternative
equipment is available which prevents the catastrophic result; and 3)
my existing equipment is ready to be replaced, I, like any rational
person, will purchase the upgraded equipment.
Meanwhile, I will continue to use the components which have worked
flawlessly for 3 years while I had my head buried in the sand with the
same lack of concern.
--dt
James Annan
> As a "bloke [or "dude'" on USA side of the pond)-on-a-bike type who
> has ridden thousands and thousands of miles off-road with disc brakes
> without a QR release, knows hundreds of people who have ridden many
> more thousands and thousands of miles with disc brakes without a QR
> release, here is what I glean as an ignorant and stupid layman from
> the conclusions of Annan and Brandt:
>
> If you ride some unspecified but significantly large amount of miles
> with disc brakes, the QR eventually will loosen to a degree that it
> could pop over the dropout tabs and the wheel will fall off.
I see others have replied, but I'd just like to point out that I did not
and do not assert this. Surely many individual cases are completely
safe. If a particular QR bites into a particular fork sufficiently that
it cannot ever move at all under any realistic force, then that case
will not fail by this method.
Quite possibly your fork and QR fall into this category. Quite possibly,
the majority do, but demonstrably many do not. I see no reliable method
of distinguishing them a priori.
Maybe you should ask your 'hundreds of people' if any of them have ever
experienced their wheel slipping at all. That is the first step on the
way to failure, and the whole process can happen (and has been reported)
on a single descent. Once it starts to loosen, this can accelerate very
rapidly.
James
James Annan
> You are
> presenting as 'results' some calculations which no technical journal on
> earth would publish.
Well you are right on one point. It's certainly unpublishable, but the
reason is that it is entirely trivial. All I have done is apply a simple
calculation to a straightforward high-school level problem (or lower),
which apparently has not been properly considered before. Which makes it
all the more disappointing that so many people fail to understand it! I
guess one should never underestimate the audience...
> At this point all
> you are doing is screaming that the sky is falling.
I repeat for the hard of understanding: I don't know what the failure
rate is. I do know of several cases where severe injury has occurred,
apparently due to this failure. I note that 10 million bridgestone tyres
'only' generated a handful of serious crashes, but were still considered
faulty as a result. Doubtless you would prefer to still be driving on them.
My wife will be very upset that you do not like her picture. But the
photograph of Fuji-san is rather good, don't you think?
James
Tim McNamara
Doug Taylor <tayl...@choiceonemail.com> wrote:
> garyy...@hotmail.com (Gary Young) wrote:
>
> >Given the fact that the consequences of this type of failure can
> >be quite severe, what is your problem with encouraging
> >manufacturers to fix it?
>
> Absolutely none. Did you pay attention to the entire thread? Do
> you have reading comprehension problems?
Apparently you have some sort of reading impairment, however. You
certainly do not read with due attention- I hope you are more alert
when you ride your bike.
> My point was and is that the minuscule theoretical chance that my
> front wheel "could" fall off due to QR failure does NOT impel me
> immediately to stop riding my mt. bike as it currently is equipped,
> or to buy new equipment. The cost is inversely proportional to the
> benefit. My QR can be and is adjusted with enough frequency to
> avoid the predicted (by rarely encountered in fact) result.
It is not a miniscule theoretical chance, which you would understand
if you had been paying attention.
> Anyone who is so frightened by Annan's theory that he or she locks
> his current bike in the basement waiting for the cure is
> overreacting in the extreme.
You are the only one advocating this interpretation. This suggests
that (1) you're a hysteric or (2) you are trying to distort what James
Annan has written in order to prove yourself right. I suspect it's
the latter.
> If and when: 1) the theory is proven to be correct; 2) alternative
> equipment is available which prevents the catastrophic result; and
> 3) my existing equipment is ready to be replaced, I, like any
> rational person, will purchase the upgraded equipment.
(1) The theory appears quite reasonable and has been proven in a
number of field tests. Unfortunately those folks didn't know they
were doing field testing, sort of like buying a Microsoft product.
Fortunately for those using the latter, you'll only be inconvenienced
if it fails in some way. (2) Alternate equipment is available- it's
called a rim brake. There are several different designs from which to
choose- lighter, safer and less expensive than disk brakes. (3) Only
you can decide when the equipment is ready for replacement.
> Meanwhile, I will continue to use the components which have worked
> flawlessly for 3 years while I had my head buried in the sand with
> the same lack of concern.
Well, then, good luck. After all, it's your cost-benefit ratio. But
I very much doubt you will use it with the "saame lack of concern."
You're going to just double check that QR or clamp it down just a
smidge tighter, make sure there's no dirt on the clamping areas, etc.
That's just human nature.
Maki
still_th...@hotmail.com (James Annan) wrote:
> It's a pretty standard estimate, and I didn't want to go to extremes -
> that would only have led (even more) people to say I was exaggerating
> and scaremongering. It's not critical to the calculation.
<disclaimer>I'm not an engineer and I'm not english, so maybe I'm not
expressing myself correctly below. However I'd like to hear your opinion
on some points that IMHO should be considered. If what I write isn't
clear or seems incorrect, please tell me and I'll try to rephrase it. Of
course maybe I'm simply dead wrong.</disclaimer>
I think you reasoning on the problem, while basically correct, is in
some way "reversed" and grossly oversimplified. You start with the
deceleration and end up with the forces. In real life you apply a force
on the brake lever and you end up with a deceleration. As far as the
calculations are concerned it works in both ways, but the reversed
reasoning may lead to erroneous conclusions. Lets see what I mean.
When you squeeze the brake lever your force is transmitted (and
multiplied) to the brake calipers that push the pads against the disc,
thus generating a frictional force on the disc. This generates a
reaction force (that acts as a disengaging force) on the wheel axle with
the same magnitude (actually IMHO less, see below). If the braking force
is greater than the grip of the QR surfaces the axle moves, if not it
stays in place. That's all there is to it: *the disc diameter is not
relevant*.
If you know the friction coefficient of the brake pads you can easily
calculate the force: if you, as me, don't know it of course you have to
apply your "reversed" formula to real world measures (wheel and disk
diameter, deceleration and mass). However, once you've got the numbers
you should not consider the disk diameter or the mass anymore, instead
you continue to consider the deceleration as a constant. Given the same
caliper+pads+pump and the same force on the lever, changing the disk or
the mass of the cyclist results in a different deceleration, and in real
world situations the constant is the braking system, not the
deceleration.
If you double the wheight you don't double the disengaging force, but
halve the deceleration. So when you say that the same brake on a tandem
is more challenged it is not entirely true, since of course you can
increase the force on the lever to compensate the increase in mass, but
not that much.
Saying that systems with a smaller disk are more prone to failure isn't
really correct either. People that wants to brake hard use big disks for
a reason, that is given the same caliper the wheel/disk ratio is better.
Also with larger disks calipers tend to be bigger (i.e. more piston
surface), thus giving a greater force with the same fluid pressure. A
bigger disk isn't really safer, in some cases it can be even worse. To
be more clear: I dont't think that a 165mm XC disc is ever going to be
used in a 0.6g deceleration and anybody using it in a DH race with a 6
piston caliper system has bigger problems in his head than on his bike.
Some other considerations:
- I said above that the reaction force is less than the braking force.
In your calculation you consider the wheel free to rotate around the
caliper. It is not, there is a *strong* friction on the pads that works
against that. I don't know how to calculate that force, but you can
simply try to move your wheel with the brake sqeezed and the axle
removed to see.
- Real world QRs. The PDF that you quote is too old. After those tests
were made the ISO standard has been updated. Still the test shows that
most if not all the QRs tested exceded *by far* the requirements, some
even reached the double of todays standards. This is pretty common,
engineers always consider a "security coefficient" when they do their
math. I expect todays QRs to be much better than pre-1996 ones. I've
read nearly all the links you give, as well as past threads on the
subject and as a metter of fact most if not all the people that has had
problems solved them changing their vendor. This leads me to think that
revamping the ISO standards is probably a Good Idea, but the real point
here is: who verifies the application of the standards? Good QRs are
already good enough.
- Real world data: 0.6g means that you stop a bike running at 50Km/h in
14 metres. Do you really do that? off road? with a 165mm disk? I haven't
done the math because I don't know where the GC is, but IMHO you are
near the physical limit of a MTB *on flat land* assuming a good grip
(asphalt). Running downhill the limit is lower. The steeper the
downhill, the lower the limit: at some point you can't even brake
because you do catapult.
- I never liked QRs even if I'm still with V-Brakes. They just look
fragile to me, but maybe I'm just used to motorcycles. I like
through-axle hubs better especially in hard riding. I think that most of
the people who is pushing the limits already adopted through-axle
solutions because, brakes aside, they are stiffer and more reliable.
People doing XC don't brake that hard ina any case.
I'm not saying that your theory is wrong, but the practice shows that
thousand of bikers are using disk brakes without ever seeing this
problem. I think the above points can, at least partially explain the
difference between theory and practice.
IMHO you should back up your assertions with a more complete and
accurate math model (and especially real data about current QRs
performance), or lower the tones on the argument, because you are
spreading terror without any real reason: reading your pages it seems
that all the QRs are going to fail eventually, which is unlikely. IMHO a
properly designed and used QR is not going to disengage and I can't
believe that nobody between the people with years of experience involved
in designing brakes, forks and hubs has ever considered the issue. And I
don't think they are afraid to adopt a new standard, as they always
search excuses to make us change everything.
As said I'd like to hear your (and other's people here) opinion on the
aabove considerations.
--
Fact of life #15: Heads bleed, walls don't.
Tim McNamara
two legs of the fork do not necessarily move equally, resulting in
complaints of vagueness of steering, etc. There have been various
attempts at overcoming this, including inverting the stanchion and
slider, adding large cross-braces, etc.
Now, if one leg compresses farther than the other, doesn't this add a
bending stress to the skewer and possibly complicate the problems
raised by James Annan?
Maki
Tim McNamara <tim...@bitstream.net> wrote:
> As far as I can tell, simply locating the caliper in front of the fork
> would eliminate this problem. Or even moving it around the rotor so
> the resultant force isn't in line with the dropout might help; surfing
> around on motorcyle Web sites suggests that those manufacturers have
> already sussed this issue- their placement of calipers tends to be at
> the top of the rotor (e.g., see the Harley Web site), analogous to the
> placement of rim brakes, as a matter of fact.
ROTFL. Since when Harley is supposed to make motorcycles? :)
Seriously, every high performance motorcycle made in the last 20 years
that I can think of, be it road or off-road, has the calipers in the
very same position of any MTB fork. It just works better this way. And
motorcycle forks don't have dropouts.
Jon Isaacs
>I think you reasoning on the problem, while basically correct, is in
>some way "reversed" and grossly oversimplified. You start with the
>deceleration and end up with the forces. In real life you apply a force
>on the brake lever and you end up with a deceleration.
I think James has done this correctly. He does not need to know how hard you
pull on the brake lever.
He starts at the ground and notes that a bike will flip over if it decellerates
at more than 0.6 gs. Thus he has a limit here.
As long as the brake is capable of stopping at .6 gs, then this is a reasonable
assumption.
Trying to work the other way such as you propose, involves many estimations
that have no meaning because in the end, all that matters is that brake is
capable of achieving a 0.6 g decelleration which is I believe is a reasonable
assumption for a disk brake.
>If the braking force
>is greater than the grip of the QR surfaces the axle moves, if not it
>stays in place. That's all there is to it: *the disc diameter is not
>relevant*.
I believe you need to draw a freebody diagram and see how these forces and
levers interact. There are two levers here both centered about the axle. One
is the distance from the axle to the contact patch on the road, the other is
the distance from the axle to where the caliper grips the disk. The braking
force is multiplied by that ratio of these levers and this is the force which
is pushing on the QR.
>Given the same
>caliper+pads+pump and the same force on the lever, changing the disk or
>the mass of the cyclist results in a different deceleration, and in real
>world situations the constant is the braking system,
The limit again is independent of the riders mass, in the real world, more
massive riders pull harder on the brake levers.
Jon Isaacs
Jon Isaacs
>
>So is a front tire flat.
Sorry but I have many front flats in some fairly critical situations but I have
never gone down because of a front flat.
Loosing a front wheel is a whole different story, you are going down and going
down hard.
>Both people who flatted in front crashed bad, and no need to get into
>it.
It is certainly possible to be riding in a manner such that a front flat is
critical.
However it is basically impossible to be riding in a manner such that losing a
front wheel will not be catastrophic.
>If indeed the fix is simple and no cost, no one would possibly argue
>with you. Bring it on; I'll take it.
Manufacturers only need to place the caliper in front of the fork rather than
behind it. This means that when the brakes are applied, the wheel is pushed
into the dropout rather than out of the dropout.
>But please elaborate. Right now I have expensive forks and disc
>brakes. To replace them would cost well over a $500 (no need to get
>into that either). Sorry, but the cost exceeds the benefit. I don't
>need to replace them immediately; I can be vigilant that my QR is snug
>before I ride and be utterly safe and care free (other than of the
>REAL risks of the sport.) When I replace them in due course, and if
>the industry has redesigned and improved the system, I will certainly
>by the state of the art.
>
>--dt
I cannot make a decision for you. Only you can access the risks. If I owned a
bike with Disk Brakes, I would probably be reluctent to start again.
The basic point is that there is good reason to be concerned and aware,
something few people were prior to James' efforts. In your situation care and
awareness are most likely sufficient.
But there are plenty of people who do not read this newsgroup who are unaware
of this design flaw.
It ought to fixed and if it is, then I expect it will be at least partially due
to James' efforts.
Jon Isaacs
James Annan
>
>>A front wheel falling off is a catatrophic event.
>
>
> So is a front tire flat.
I've done both, and believe me, they do not compare. A slide-out at
30mph means road-rash, unless you are very unlucky. A wheel loss at
15mph slams you headfirst into the ground.
> But please elaborate. Right now I have expensive forks and disc
> brakes. To replace them would cost well over a $500 (no need to get
> into that either). Sorry, but the cost exceeds the benefit.
I suspect you will not be bearing that cost yourself.
James
Carlton Reid, BikeBiz.co.uk
problem with folks cutting-and-pasting all the QR/disc brake articles
I've done. There's been three to date. More will no doubt follow.
You'll see that the articles include lots of question marks and
'maybes' and words like 'theory'. I don't think the pieces are
sensationalistic. But if there's a real QR problem out there, and I
incline to think there is, I want the bike trade to do something about
it.
The problem is fixable, so let's fix it.
Andreas Oehler
>Seriously, every high performance motorcycle made in the last 20 years
>that I can think of, be it road or off-road, has the calipers in the
>very same position of any MTB fork. It just works better this way.
Please explain why. I don't see a reason. Important for the braking are
the diameter of the disc, the force of the pads pressed on the disc, the
coefficient of friction (and to some degree heat transfer, wear, stiffness
of the mount).
A friend has two bikes equipped with Sachs Powerdisc (the first mass
produced hydraulik disc brake for bicycles). The brake caliper is mounted
to the front of the fork. See it on
http://www.enhydralutris.de/Fahrrad/HPV-Bilder/OlafSchultz/ATB/index.html
http://www.objectfarm.org/People/Tomi/HPV/Photos/GreenAmigo.406.Side.Photo.jpg
The brake is a little too heavy but works extremely well.
> And
>motorcycle forks don't have dropouts.
Yes. Without dropouts it is no problem to have reaction forces, which try
to move the axle down.
Andreas
Doug Taylor
(2) Alternate equipment is available- it's
> called a rim brake. There are several different designs from which to
> choose-
Cantis, which modulate but don't stop, or V-s, which stop but don't
modulate...
Annan, with justification I admit, decries the "bloke-on-a-bike" who argues
against his theory out of emotion and without knowledge or critical
reasoning in support. Only thing worse is you: a "bloke-off-a-bike" who
appears to be blowing smoke. If you ride off-road more than a few times a
month, I'll eat my QR. The majority of riders who spend a lot of time on
mountain bikes use discs because of superior performance: stopping power
AND modulation (old thread). They will not be quick to spend gobs of cash
(see below) replacing them with inferior equipment unless and until there is
a real reason to.
> lighter
Ever hear of XTR? Negligably heavier than V-s; standard equipment in 2003
for world cup x-c racers who use Shimano group.
>safer
A theory has been proposed, which appears to be sound on paper. There is
anecdotal evidence to support it, and that which does not. It has yet to be
"proven" by actual testing and measurement. Annan will admit as much, I
wager.
>and less expensive than disk brakes.
Not if you are going to revamp your current system in reaction to the
theory. That will run you new wheels as well as new brakes. Cost exceeding
benefit.
>> You're going to just double check that QR or clamp it down just a
> smidge tighter, make sure there's no dirt on the clamping areas, etc.
> That's just human nature.
Well, duh! That will fix the problem for the time being. And doesn't cost
a dime.
B. Sanders
news:vcdd8f5...@corp.supernews.com...
> "Tim McNamara" <tim...@bitstream.net> wrote in message news:timmcn-
>
> (2) Alternate equipment is available- it's
> > called a rim brake. There are several different designs from which to
> > choose-
>
> Cantis, which modulate but don't stop, or V-s, which stop but don't
> modulate...
>
> Annan, with justification I admit, decries the "bloke-on-a-bike" who
argues
> against his theory out of emotion and without knowledge or critical
> reasoning in support. Only thing worse is you: a "bloke-off-a-bike" who
> appears to be blowing smoke. If you ride off-road more than a few times
a
> month, I'll eat my QR. The majority of riders who spend a lot of time on
> mountain bikes use discs because of superior performance: stopping power
> AND modulation (old thread). They will not be quick to spend gobs of cash
> (see below) replacing them with inferior equipment unless and until there
is
> a real reason to.
>
> > lighter
>
> Ever hear of XTR? Negligably heavier than V-s; standard equipment in 2003
> for world cup x-c racers who use Shimano group.
I have XTR stuff all over my bikes. What do you mean by "negligibly
heavier?" Let's see some numbers for total bike weight with discs vs. same
bike with superlight V-brakes. If there's less than 1.5 pounds of
difference, I'll eat my hat. It's more like 2 lbs of difference. There are
no superlight disc-equipped bikes, AFAIK.
> >safer
>
> A theory has been proposed, which appears to be sound on paper. There is
> anecdotal evidence to support it, and that which does not. It has yet to
be
> "proven" by actual testing and measurement. Annan will admit as much, I
> wager.
>
> >and less expensive than disk brakes.
>
> Not if you are going to revamp your current system in reaction to the
> theory. That will run you new wheels as well as new brakes. Cost
exceeding
> benefit.
I'm avoiding the whole problem by simply not using discs. How is that more
expensive? I'd say it sounds like discs already have a cost that well
exceeds benefit, on every score.
> >> You're going to just double check that QR or clamp it down just a
> > smidge tighter, make sure there's no dirt on the clamping areas, etc.
> > That's just human nature.
>
> Well, duh! That will fix the problem for the time being. And doesn't
cost
> a dime.
My $40-per-bike basic Avid V-brakes outperform my $200-per-bike* Avid discs
on every score, including modulation, and don't require off-center dishing
on the front wheel as front disc hubs do. The Avid V's are also 2 *pounds*
lighter (including extra wheel and fork weight) than the discs. I can think
of better things to do with $500 than put XTR disc brakes on my bike and add
2 lbs of weight in the process. BTW: With V-brakes, I rarely locked up the
wheels unintentionally. With discs, I do it all the time. So what were you
saying about "superior modulation?" Please cite studies to document this
superiority, including population studies of riders who prefer and use discs
over V-brakes.
Barry
* Total cost to switch to discs is more like $350 to $400, since equivalent
quality disc-compatible wheels, calipers and rotors must be purchased. This
of course also presumes that the frame is disc ready.
Jon Bond
"B. Sanders" <ba...@bsanders.net> wrote in message
news:NoAxa.919922$S_4.931139@rwcrnsc53...
>snip<
> > Ever hear of XTR? Negligably heavier than V-s; standard equipment in
2003
> > for world cup x-c racers who use Shimano group.
>
> I have XTR stuff all over my bikes. What do you mean by "negligibly
> heavier?" Let's see some numbers for total bike weight with discs vs.
same
> bike with superlight V-brakes. If there's less than 1.5 pounds of
> difference, I'll eat my hat. It's more like 2 lbs of difference. There are
> no superlight disc-equipped bikes, AFAIK.
>snip<
Ok, trying to compare very similar components, so we'll go Crossmax SL's
(disc/nodisc) and new XTR. I am, however, using manufacturer's specs, but
we'll figure they're pretty much off the same since its the same companies.
DISC SETUP
Crossmax SL Discs - 1685g
'03 XTR Shift/Lever - 442g
XTR Disc Brakes (F+R)- 198g
Stan's Rotors (F+R) - 108g
Total - 2433g
5.36lbs
NON DISC Setup
Crossmax SL - 1500g
'03 XTR Shift/Lever - 412g
XTR V-Brake pair - 398g
Total: 2310g
5.09lbs
That's only just over a quarter pound difference. Even if they aren't
counting bolts and cables, which will almost even out, maybe add a bit more
to the discs, you're still well under a pound.
Sorry, hope you like the taste of hat. You can use ketchup if you want.
Jon Bond
Mark McMaster
> "Tim McNamara" <tim...@bitstream.net> wrote in message news:timmcn-
>
> (2) Alternate equipment is available- it's
>
>>called a rim brake. There are several different designs from which to
>>choose-
>
>
> Cantis, which modulate but don't stop, or V-s, which stop but don't
> modulate...
>
> Annan, with justification I admit, decries the "bloke-on-a-bike" who argues
> against his theory out of emotion and without knowledge or critical
> reasoning in support. Only thing worse is you: a "bloke-off-a-bike" who
> appears to be blowing smoke. If you ride off-road more than a few times a
> month, I'll eat my QR. The majority of riders who spend a lot of time on
> mountain bikes use discs because of superior performance: stopping power
> AND modulation (old thread). They will not be quick to spend gobs of cash
> (see below) replacing them with inferior equipment unless and until there is
> a real reason to.
>
>
>>lighter
>
>
> Ever hear of XTR? Negligably heavier than V-s; standard equipment in 2003
> for world cup x-c racers who use Shimano group.
According to Velonews, Shimano sponsored racers are required
to use the Shimano disk brake. In other words, Shimano disk
brakes are being used by pro racers not because they are
necessarily better, but because they are contractually
obligated to use them.
That points out the irony about contractual sponsorship
agreements that seems to be lost on the buying public: It
is hardly a strong endorsement for a product if they have to
pay people to use it.
Mark McMaster
MMc...@ix.netcom.com
B. Sanders
news:0HAxa.920133$S_4.931192@rwcrnsc53...
What's the performance of this setup? Are 108grams/pair rotors reliable?
Bet they get pretty hot and warp like crazy. I had excellent CNC'd brakes
on my Merlin that were about 280g/set, which adds another 1/3 of a pound to
your total weight difference. Also, let's see real-world weight measurements
on those components. Under 200 grams for both front and rear for XTR
calipers? With hoses? Yeah, right.
So, the moral of the story is that if you live in the upper stratosphere of
componentry, and have a *HUGE* budget for wheels and brakes, then *maybe*,
just maybe you might not totally screw up your bike with disc brakes.
You'll still add almost half a pound to your superlight steed, and your
front wheels will be dished. But hey, you'll sport the latest fad, and
that's worth a lot, isn't it? Oops! You seem to have ripped loose one of
those super-light hydraulic hoses on a tree branch, and now your brakes are
useless. Guess you'd better order another $50 hose and wait a couple of
weeks for delivery.
Why should I switch from V-brakes? To make an $800 fashion statement? Still
haven't seen any compelling evidence for disc superiority (and yes, I have a
disc equipped bike with roughly equivalent components to my V-equipped
bike).
Barry
Jon Bond
No, actually, I've heard plenty of good things about 'em. Only thing you
need to do is get a different pair of brake pads because the normal ones
don't work with aluminum. Plus, if you've got a superlight bike anyway,
you're automatically sacrificing some reliability for performance.
> I had excellent CNC'd brakes
> on my Merlin that were about 280g/set,
With mounting bolts, Noodle, fixing bolt, etc?
> which adds another 1/3 of a pound to
> your total weight difference. Also, let's see real-world weight
measurements
> on those components. Under 200 grams for both front and rear for XTR
> calipers? With hoses? Yeah, right.
The brake calipers themselves are under 200 grams - and I clearly stated
that I did not include cables/hoses. Hydraulic hoses are not ALL that
heavier than non-hydraulic hose - You've just got metal and plastic around
fluid instead of metal and plastic around metal, and a bit more length.
> So, the moral of the story is that if you live in the upper stratosphere
of
> componentry, and have a *HUGE* budget for wheels and brakes, then *maybe*,
> just maybe you might not totally screw up your bike with disc brakes.
> You'll still add almost half a pound to your superlight steed, and your
> front wheels will be dished.
Oh, give me a break, Barry. you're reaching here. First off, I'm more than
willing to trade half a pound (by your measurements and assumptions, not my
actual component weights) for better braking. And yes, I've used both, more
than once. If you like riding your bike down as well as up, then discs are
nice. Go race the XC course at Plattekill, NY next year and tell me disks
wouldn't be nice. After a few mud crossings, I had to break WAY in advance,
and I ate through almost a quarter of my pads in just one lap.
And, oh no, not a dished front wheel! The spoke lengths will be almost 1mm
different! (.9mm by Slacker's current wheelbuild project). Remember, this
is a superlight bike - you're not going to be doing any crazy drops on it
unless you've got a few screws loose. And, oh my, wait for it, the rear will
actually be dished LESS! Imagine that.
> But hey, you'll sport the latest fad, and
> that's worth a lot, isn't it? Oops! You seem to have ripped loose one of
> those super-light hydraulic hoses on a tree branch,
Same as ripping loose one of those superlight cables. Seriously, all the
detractors of disc brakes bitch about how easy it would be to rip a hose
off. But wait, can't those disc hoses have less loops to catch things,
because they can take sharper bends than cables can? Hey, look at that.
Also, how many people have ACTUALLY ripped a disc hose loose? If you catch
something with enough force, you're just as likely to rip a normal cable
apart as you are a hydraulic cable.
> and now your brakes are
> useless. Guess you'd better order another $50 hose and wait a couple of
> weeks for delivery.
>
> Why should I switch from V-brakes? To make an $800 fashion statement?
Still
> haven't seen any compelling evidence for disc superiority (and yes, I have
a
> disc equipped bike with roughly equivalent components to my V-equipped
> bike).
Seems to me like somebody doesn't ride where you're inevitably going to have
to cross a stream or a bit of mud. And in case you're wondering, my current
bike is equipped with Avid Arch Rival 50's with koolstop pads, so they're
not cheap, flimsy brakes.
> Barry
I don't see you eating hat - either way "Half a pound" (again, by your
estimation instead of my factual numbers) is still well under 1.5 lbs.
Start chowing down, Barry. Acutally, don't - then you'll save that entire
half a pound that you just added to your bike from going to your gut.
Oh, and by the way - "There are no superlight disc-equipped bikes, AFAIK"
http://light-bikes.com/gallery/anders.htm 19.42lbs hardtail
http://light-bikes.com/gallery/jul.htm 20.63lbs hardtail
http://light-bikes.com/gallery/wfl3_giant.htm 20.94 lbs hardtail
http://light-bikes.com/gallery/brentd.htm 19.56 lbs hardtail
http://light-bikes.com/gallery/sunny.htm 23.23 lbs full suspension
(Ellsworth Truth)
http://light-bikes.com/gallery/wfl3.htm 23.68 lbs full suspension (another
Truth)
http://light-bikes.com/gallery/anders_sl.htm 22.51 lbs full suspension (SC
Superlight)
http://light-bikes.com/gallery/az_x_racerx.htm 22.41 lbs full suspension
(Titus Racer-X)
http://light-bikes.com/gallery/ethan.htm 22.75 lbs full suspension
(Specialized Epic)
and so on, and so on, and so on.
Jon Bond
B. Sanders
>
> "B. Sanders" <ba...@bsanders.net> wrote in message
> news:4SAxa.873771$3D1.498250@sccrnsc01...
> > "Jon Bond" <Jonath...@REMOVEtufts.edu> wrote in message
> > news:0HAxa.920133$S_4.931192@rwcrnsc53...
> > >
> > > "B. Sanders" <ba...@bsanders.net> wrote in message
> > > news:NoAxa.919922$S_4.931139@rwcrnsc53...
> > > >snip<
Do you have any scientific studies or real-world side-by-side tests to
support your "disc brakes are better" assertion? (After all, I'm not the
one advocating discs here. You are.) So far, all I've heard are anecdotal
raves by disc brake evangelists, with zero substantial evidence to back it
up. Aside from appeals to fashion sense, and anecdotal evangelism, what
will compel me to pull that $500+ out of my pocket? Let's assume that I
don't mind adding anywhere from 1/2 to 1 1/2 pounds to my bike.
What if I almost never ride in sloppy mudpits or long downhills? Why should
I even consider disc brakes?
Barry
Jon Bond
If you need "scientific studies", then you're thinking too much. If you
want a real world comparison, and don't trust the thousands with "anecdotal
evidence", then go ride a bike with high quality discs, and then a similarly
set-up bike with V-brakes. As for the cost, if you're buying a new bike its
nowhere near that much of a difference, unless you're going from shit V's to
top quality discs. And seriously, if you're so into superlight bikes, then
you've got a pretty deep wallet anyway. Oh yeah, and your hat-eating phrase
never said anything about price difference. Think of it as more weight out
of your wallet.
I'm not advocating disc brakes for all applications, but my personal
experience is that disc brakes modulated better than my V brakes with
similar power - and you only need so much power to brakes, after all, the
tires can only have so much traction. And I didn't have buyer's blindness
(I just spent $800, so it MUST be good!), because it was a rented bike - and
for that matter, I didn't really like the bike itself that much. This was
out in AZ too, in Phoenix's South Mountain park, so I didn't have any really
long downhills or mud pits to deal with. That was my first experience -
since then, I've ridden a lot of (borrowed/demo) bikes both with discs and
with various V's.
Anyway, you still ignored my first post - it was purely numbers, I said
nothing about disc brakes and their performance, or lack of, for that
matter. No matter what I feel - our hypothetical disc equipped bike is
still well under your 1.5lb hat-eating difference.
If you don't want to ride disc brakes, then more power to ya. But don't
deny that disc brakes are getting lighter. Oh, and by the way, I enjoyed
the way you ignored ALL of my points from the last post with one giant snip.
Wassamatter, truth hurts?
Jon Bond
B. Sanders
Should I take that to mean "there is no evidence?" Thought for sure there
might be some "V-brake vs. Disc" shootouts in the industry mags. (Oh, I
forgot: Those mags are designed to *sell* the latest gadgets, not debunk
them.)
> If you
> want a real world comparison, and don't trust the thousands with
"anecdotal
> evidence"
Do you mean the same thousands who jumped all over tubeless tires, only to
find out that they were a PITA? There's always some sexy, techie new "must
have" gadget. Some pan out, some don't. Discs are getting lighter and
cheaper; but I'm not convinced they're actually substantially better, nor do
I believe they're worth the additional weight and huge expense (for
upgrading existing bikes it's something like $350 - $500, with XTR/CrossMax
being substantially more). If you like discs, great. I've tried 'em, and
I'm not noticing any difference that's worth mentioning. I'll try the XTR's
and Hope's when I find a bike that has 'em.
> then go ride a bike with high quality discs, and then a similarly
> set-up bike with V-brakes.
Already did that. I like the V-brakes better. V-brake pads are 1/4 the
price and much easier to find, too.
> As for the cost, if you're buying a new bike its
> nowhere near that much of a difference, unless you're going from shit V's
to
> top quality discs.
Usually, it's going from good V's to decent discs for a significant price
jump and significant weight increase (overbuilt wheels, heavier brakes).
Only untouchably expensive bikes have high-end disc brakes.
> And seriously, if you're so into superlight bikes, then
> you've got a pretty deep wallet anyway.
Well, it all depends on how and where you shop. Used lightweight bikes can
be inexpensive if you shop smart.
> [you]
> never said anything about price difference. Think of it as more weight
out
> of your wallet.
I'll think of it as something I can happily live without, like most cyclists
who aren't duty-bound to the latest bike swag fashion. I won't be building
any more disc bikes for a while. Wouldn't mind trying the XTR's at some
point.
> I'm not advocating disc brakes for all applications, but my personal
> experience is that disc brakes modulated better than my V brakes with
> similar power
I'll wait for some real-world tests with riders who aren't emotionally
invested or legally bound to using disc brakes. I'm also interested in
finding out about stresses on the wheels from disc brakes, and failure modes
associated with those stresses.
-Barry
Tim McNamara
"Doug Taylor" <dta...@dreamscape.com> wrote:
> "Tim McNamara" <tim...@bitstream.net> wrote in message news:timmcn-
>
> > (2) Alternate equipment is available- it's
> > called a rim brake. There are several different designs from
> > which to choose-
>
> Cantis, which modulate but don't stop, or V-s, which stop but don't
> modulate...
Then you have never ridden properly set up cantis. They stop every
bit as well as V-brakes (which do not exist to stop bikes better, BTW,
they exist to make bikes cheaper to build and to solve cable routing
problems with suspension forks and rear suspension). Once you've
locked up the tire, all brakes are equal.
> >> You're going to just double check that QR or clamp it down just
> >> a
> > smidge tighter, make sure there's no dirt on the clamping areas,
> > etc. That's just human nature.
>
> Well, duh! That will fix the problem for the time being. And
> doesn't cost a dime.
"Fix" the problem? No. Minimize it? Yes.
Mike S.
> > > (2) Alternate equipment is available- it's
> > > called a rim brake. There are several different designs from
> > > which to choose-
> >
> > Cantis, which modulate but don't stop, or V-s, which stop but don't
> > modulate...
>
> Then you have never ridden properly set up cantis. They stop every
> bit as well as V-brakes (which do not exist to stop bikes better, BTW,
> they exist to make bikes cheaper to build and to solve cable routing
> problems with suspension forks and rear suspension). Once you've
> locked up the tire, all brakes are equal.
>
> > >> You're going to just double check that QR or clamp it down just
> > >> a
> > > smidge tighter, make sure there's no dirt on the clamping areas,
> > > etc. That's just human nature.
> >
> > Well, duh! That will fix the problem for the time being. And
> > doesn't cost a dime.
>
> "Fix" the problem? No. Minimize it? Yes.
That assumes that there IS a problem, and not just "user error." "We" have
yet to determine whether there's a problem or not.
Mike
Dave Stocker
2 lbs of weight in the process. BTW: With V-brakes, I rarely locked up the
> wheels unintentionally. With discs, I do it all the time. So what were
you
> saying about "superior modulation?" Please cite studies to document this
Actually Barry, I think modulation comes down more to the quality of brakes
within the V- or disc family. I have a 17% grade (paved unfortunately) on
one segment of my commute to work. In just 50 meters or so, I can easily
get up to 50-55kmph. The problem is that I do not have a run out at the
bottom. I have to turn right.
The XT V-s on my old trail bike (now the main commuter) never have a problem
with modulation. I only have problems in the rain due to diminished braking
performance.
My crappy Tekpro V-s on the beater (which I am commuting on until I replace
the split rear rim on the other bike) lock up all the time. No matter how
far I hang my butt over the rear tire, I am always in a touchy balance
between rear lockup an endo.
The new trail bike with Hayes Hydros never has any modulation problems on
that section.
These disc-rim brakes take on a religious fervor. I accepted the weight
penalty for consistent all weather performance and one finger braking - I
can firmly hold the handlebar on a rough downhill with just my birdie finger
on the brakes. The first part is climate dependent. I am in Northern
Europe. Your mileage may vary...
-Dave
Juho Huttunen
> support your "disc brakes are better" assertion? (After all, I'm not the
Yes. A German magazine called BIKE ran some laboratory tests of diskbrakes
and V-brakes a while ago. You can see the results at:
http://forums13.consumerreview.com/crforum?5...@121.bhbIaX9vzkg.7@.ef946c3/4
It ended up as a huge fight, like it always seems to do with the brake issue. It
runs down to your preference and riding conditions. I ride in a climate where there
are sub zero (celsius) temperatures for four to five months a year and to me diskbrakes
are a natural choice, they just work far better in _my conditions_.
James Annan
> A theory has been proposed, which appears to be sound on paper. There is
> anecdotal evidence to support it, and that which does not. It has yet to be
> "proven" by actual testing and measurement. Annan will admit as much, I
> wager.
More evidence is always nice, but it's already proven beyond reasonable
doubt IMO, let alone on the balance of probabilities (the relevant
confidence level in the UK). Bear in mind that I also have a mailbox
full of the same stuff, which is essentially the same as that quoted.
The only value of more evidence is in convincing other people, which
would be nice but is not essential. In a world where 10% of Americans
believe they have been abducted by aliens, it would be foolish to expect
unanimity.
James
SuperSlinky
> Do you have any scientific studies or real-world side-by-side tests to
> support your "disc brakes are better" assertion? (After all, I'm not the
> one advocating discs here. You are.) So far, all I've heard are anecdotal
> raves by disc brake evangelists, with zero substantial evidence to back it
> up. Aside from appeals to fashion sense, and anecdotal evangelism, what
> will compel me to pull that $500+ out of my pocket? Let's assume that I
> don't mind adding anywhere from 1/2 to 1 1/2 pounds to my bike.
>
> What if I almost never ride in sloppy mudpits or long downhills? Why should
> I even consider disc brakes?
My own anecdotal experience has been that either type of brake will do
the job, but disc brakes make me more confident in using the brakes. I
always hated the sickening scraping sound of vibrates on the rim after
going through a puddle on a trail. I don't see how you can do much trail
riding at all without hitting at least one low muddy spot per ride.
Maybe if you lived in a desert. My front vibrate usually squealed,
actually screamed would be a better word, regardless of pads or
adjustment technique. Then sometimes the squeal would just stop for a
while. I think there is a lot more modulation with my discs than my V's,
but for that very reason the V's react quicker, which is sometimes what
you want.
B a r r y B u r k e J r .
>
>
> Why should I switch from V-brakes? To make an $800 fashion statement? Still
> haven't seen any compelling evidence for disc superiority (and yes, I have a
> disc equipped bike with roughly equivalent components to my V-equipped
> bike).
>
> Barry
I have several bikes equipped with "V" and disc brakes. Off-road, I'll
never go "V" again. $800? Avid mechanical can be had for $200.
Fashion statement, my-ass! The discs work much better in the rain,
after water crossings, in the snow and mud. I've worn out sets of "V"
pads in _one_ day of riding the Vermont ski areas, in addition to the
wear on my rims.
Last, but especially not least, disc brakes are not sensitive to out of
true or slightly damaged rims.
I'll gladly keep V-brakes on my road bikes, but gimmie discs off-road.
Barry
Doug Taylor
discs
> on every score, including modulation, and don't require off-center dishing
> With V-brakes, I rarely locked up the
> wheels unintentionally. With discs, I do it all the time. So what were
you
> saying about "superior modulation?" Please cite studies to document this
> superiority, including population studies of riders who prefer and use
discs
> over V-brakes.
Excuse me? You assert V-brakes outperform discs, including modulation, and
you want ME to cite studies documenting that DISCS are superior to V-s? You
claim you lock up with your discs unintentionally, but NOT with your V-s?
ROTFLMA! Dude, do you actually ride off-road? More than once a month? This
thread is being cross-posted to alt.mountain-bike where people actually RIDE
and have a clue what they are talking about. I suggest you retreat
gracefully, hop on your road bike, and stop embarrasing yourself.
Danny
back home..
Danny
"James Annan" <still_th...@hotmail.com> wrote
> Yada yada yada...
Maki
Andreas Oehler <bitte_Reply-...@gmx.de> wrote:
> >Seriously, every high performance motorcycle made in the last 20 years
> >that I can think of, be it road or off-road, has the calipers in the
> >very same position of any MTB fork. It just works better this way.
>
> Please explain why. I don't see a reason. Important for the braking are
> the diameter of the disc, the force of the pads pressed on the disc, the
> coefficient of friction (and to some degree heat transfer, wear, stiffness
> of the mount).
Sorry I wasn't clear. Yes there is no impact on braking performance. The
impact is on handling. If the caliper is on the back of the fork the
mass is nearer to the center line of the fork axis and there is less
inertia when you turn the handlebar.
Also people tend to trust more something that pushes the fork leg than
something that pulls it. It is probably only a psicological thing, but
maybe it is easier to build a stiffer system in this way.
B. Sanders
>
> "B. Sanders" <ba...@bsanders.net> wrote in message
> news:NoAxa.919922$S_4.931139@rwcrnsc53...
> >
> > My $40-per-bike basic Avid V-brakes outperform my $200-per-bike* Avid
> discs
> > on every score, including modulation, and don't require off-center
dishing
>
> > With V-brakes, I rarely locked up the
> > wheels unintentionally. With discs, I do it all the time. So what were
> you
> > saying about "superior modulation?" Please cite studies to document
this
> > superiority, including population studies of riders who prefer and use
> discs
> > over V-brakes.
>
> Excuse me? You assert V-brakes outperform discs, including modulation,
and
> you want ME to cite studies documenting that DISCS are superior to V-s?
If you expect thinking people to switch to disc brakes, from V-brakes, you
need to provide compelling evidence. If you're trying to appeal to drooling
morons with wads of cash hanging out of their pockets, I guess evidence
isn't as important.
> You claim you lock up with your discs unintentionally, but NOT with your
V-s?
That is correct. Happens all the time. If I had proper instrumentation, I'd
be glad to offer quantitative data to support my claims. For now, you can
choose to believe me, or not. I can only offer my qualitative experience as
a data point.
-Barry
B. Sanders
news:ba7hev$gu$1...@bowmore.utu.fi...
> > Do you have any scientific studies or real-world side-by-side tests to
> > support your "disc brakes are better" assertion? (After all, I'm not
the
>
> Yes. A German magazine called BIKE ran some laboratory tests of diskbrakes
> and V-brakes a while ago. You can see the results at:
> http://forums13.consumerreview.com/crforum?5...@121.bhbIaX9vzkg.7@.ef946c3/4
Thank you!!! This is exactly what I was asking for. Finally, the beginnings
of a body of evidence.
> It ended up as a huge fight, like it always seems to do with the brake
issue. It
> runs down to your preference and riding conditions. I ride in a climate
where there
> are sub zero (celsius) temperatures for four to five months a year and to
me diskbrakes
> are a natural choice, they just work far better in _my conditions_.
Then for you, discs are the better choice. I'm glad that discs solved your
problem.
Barry
B. Sanders
in message news:3EC76765...@thankyou.com...
> "B. Sanders" wrote:
> >
> >
> > Why should I switch from V-brakes? To make an $800 fashion statement?
Still
> > haven't seen any compelling evidence for disc superiority (and yes, I
have a
> > disc equipped bike with roughly equivalent components to my V-equipped
> > bike).
> >
> > Barry
>
>
> I have several bikes equipped with "V" and disc brakes. Off-road, I'll
> never go "V" again. $800? Avid mechanical can be had for $200.
So, you managed to buy a complete set of Avid disc brakes *and disc wheels*
for $200? I think you forgot to mention the price of the disc wheelset.
Gotta have disc wheels to ride disc brakes. Oh, and let's not forget the
disc-ready frame. My WTB titanium hardtail doesn't have disc tabs. Should I
sell it to go with disc brakes? I don't think so.
> Fashion statement, my-ass! The discs work much better in the rain,
> after water crossings, in the snow and mud. I've worn out sets of "V"
> pads in _one_ day of riding the Vermont ski areas, in addition to the
> wear on my rims.
If you do lots of sloppy, muddy, wet riding combined with steep descents,
then discs might be the best choice.
> Last, but especially not least, disc brakes are not sensitive to out of
> true or slightly damaged rims.
This is true.
> I'll gladly keep V-brakes on my road bikes, but gimmie discs off-road.
There are still a huge number of offroad riders for whom V-brakes are the
better option on every score, and for whom the $400+ switch to discs would
be wasted money.
Barry
Tim McNamara
"Mike S." <mikeshaw2@coxDOTnet> wrote:
> > > > You're going to just double check that QR or clamp it down
> > > > just a smidge tighter, make sure there's no dirt on the
> > > > clamping areas, etc. That's just human nature.
> > >
> > > Well, duh! That will fix the problem for the time being. And
> > > doesn't cost a dime.
> >
> > "Fix" the problem? No. Minimize it? Yes.
>
> That assumes that there IS a problem, and not just "user error."
> "We" have yet to determine whether there's a problem or not.
There IS a problem. That's been determined by the application of
well-known engineering principles. What has not been determined is
the frequency of occurance.
You can only think that there is NO problem if you are either
incapable of understanding the issues or are simply putting your head
in the sand.
Maki
joni...@aol.com (Jon Isaacs) wrote:
> >I think you reasoning on the problem, while basically correct, is in
> >some way "reversed" and grossly oversimplified. You start with the
> >deceleration and end up with the forces. In real life you apply a force
> >on the brake lever and you end up with a deceleration.
>
> I think James has done this correctly. He does not need to know how hard you
> pull on the brake lever.
Yes, it is correct, I stated this. But it seems that that the braking
force is generated by the ground. It isn't.
> >If the braking force
> >is greater than the grip of the QR surfaces the axle moves, if not it
> >stays in place. That's all there is to it: *the disc diameter is not
> >relevant*.
>
> I believe you need to draw a freebody diagram and see how these
> forces and levers interact. There are two levers here both centered
> about the axle. One is the distance from the axle to the contact
> patch on the road, the other is the distance from the axle to where
> the caliper grips the disk. The braking force is multiplied by that
> ratio of these levers and this is the force which is pushing on the
> QR.
If you have a wheel spinning off the ground and you brake you still have
the same force acting on the disk and the same reaction force on the
axle. Disks are bench-tested in this way, without even mounting spokes,
rim and tyre. The force is generated by the caliper's pads friction.
Of course, as I said, since we don't know the frictional coefficient of
the pads we have to use James formula (the levers) to get the force
magnitude from real world measures. But once we've got that value, we
must stop and not continue reasoning with a constant deceleration. We
cannot say things like:
|The smaller disc generates a larger force too.
because the force is generated by the caliper (not by the disk), and is
independent of the disk diameter. Or, about tandems:
|Firstly, they typically carry twice the weight, which immediately
|doubles the braking force.
because unless the braking system on the original single bike was *way*
oversized this is not what happens. To decelerate 160Kg at 0.6g you need
a really powerful brake, not a 165mm one. My trial motorbike (that with
me on board has more or less that weight) cannot brake that hard, with
185 mm *robust* disks *and real tyres*.
> >Given the same
> >caliper+pads+pump and the same force on the lever, changing the disk or
> >the mass of the cyclist results in a different deceleration, and in real
> >world situations the constant is the braking system,
>
> The limit again is independent of the riders mass, in the real world, more
> massive riders pull harder on the brake levers.
Not infinitely, everything has a limit. If it could be possible to get
decent performance from a brake simply increasing the fluid pressure we
would see only 100 mm disks even on motorcycles, but we don't.
User's hands, fluid pressures and pad's materials are more or less
standardized, when you need more power you use bigger disks.
My point was simply that smaller disks are not more challenging for the
QR, because piston's area, pressure and frictional coefficient are more
or less the same in every disk brake.
However, assuming James is right and QRs are bad (which is at least
plausible, even if not really demostrated since we not have reliable
data about actual QR performance) changing the dropout direction is not
a solution. Think about it, the axle is pushed *down*. But when you fit
the wheel the axle contacts the fork on the *upper* side. Since the
threaded axle has a lot of clearance in the dropout it is free to shift
quite a bit downwards, and according to James this little slippage is
enough to unscrew the QR.
If the problem is real, motorcycle-style axle apart, the only solution
is a new QR system that cannot unscrew. On the lever side it is pretty
easy to do, just make something that protrudes in the dropout so that
the QR cannot turn more than a few degrees. On the nut side it is a bit
more difficult, but not impossible. For example it can be use a special
washer: one side should protrude in the dropout, the other should have a
knurled [1] surface that matches a similarly knurled surface on the nut.
With a proper cam profile it should work quite well. The knurl should be
1 mm high or so.
[1] I'm not sure if this is a correct term, I mean something like this:
/\/\/\/\/\/\/\/\/\/\/\/\/\ <-- knurled surface
| | <-- washer body
+------+ +-------+
| | <-- protrusion
+---------+
when viewed by side and with a lot of fantasy. (use monospaced font)
Doug Taylor
>> If you expect thinking people to switch to disc brakes, from V-brakes,
you
> need to provide compelling evidence. If you're trying to appeal to
drooling
> morons with wads of cash hanging out of their pockets, I guess evidence
> isn't as important.
For every dewbie with a big wallet who buys into sheer marketing, there's an
smug retrogrouch who insists that his antiquated equipment is superior and
he is holier than the rest because he still uses it.
With apologies to St. Francis, here's a twist on the Serentity Prayer:
"Lord grant me the serenity to be able to change with the times, the
strength to resist marketing ploys, and the wisdom to know the difference."
On your knees, Barry: you need spiritual guidance.
> > You claim you lock up with your discs unintentionally, but NOT with your
> V-s?
>
> That is correct. Happens all the time. If I had proper instrumentation,
I'd
> be glad to offer quantitative data to support my claims. For now, you can
> choose to believe me, or not. I can only offer my qualitative experience
as
> a data point.
If you ACTUALLY ride one bike with v-s and another with discs regularly, and
still insist that the v-s are superior in terms of stopping power,
modulation, and not locking up, I submit you are: 1) an alien from another
galaxy; 2) one piss-poor cyclist; or 3) full of bullcrap.
Or to put it more mildly, in a very, very small minority.