damaged (cracked?) rim -- how safe (temporarily)
yirgster
rim.
Riding uphill yesterday, a rear, freewheel side spoke pulled out of
it's hole, ripping an elongated gap of nearly an inch on the
underside, about 1/2" of one side of which very slightly extends just
onto the angled portion of the rim wall (not the main nearly vertical
wall).
Didn't have any problems riding it a short distance to where my wife
picked me up and last night I re-trued the wheel so it's reasonable.
Actually, it's more true than many wheels I've seen. The rim seems
strong to the hand. But, obviously, that's "seems", not "is".
I've ordered another wheel but it won't be here to mid-next week and
I've got to have my fix. (There are worse things to be addicted to. I
hope.) So I'm wondering how safe it is to go out for short rides, even
8-10 miles, near the house. Would involve hills and descents since
that's the topology. Getting home isn't the problem if there is a
problem, but I don't think it would be too cool to have the rim
collapse on me. I don't mind taking the downhills very, very slowly.
You know, in the old days (which I'm old enough to remember too well),
you know, those days before indexed shifters and cassettes, in this
situation you'd just swap rear wheels with an old one hanging around.
Didn't matter what freewheel it was. Maybe I can re-commission one of
my ancient bikes, in various stages of disrepair, cannibalized over
the years, etc. But their gearing is definitely on the high side for
me now, to say the least.
Jay Beattie
I have pulled spokes through rims, trued the wheel and finished the
ride. I have never done that where the crack extended in to the
sidewall. That is more problematic, and I don't know what would happen
to the crack under braking forces or whether it could result in the
rim falling apart. Jobst should enlighten us on that. My unscientific
sense is that the rim would retain its hoop shape because of spoke
tension but that you would get a nasty rim crack catching your brake
pad. The good part is that it is a rear wheel, and you will not go
OTB if it fails. The deal is that you should stop riding that wheel
because crack propagation can be unpredictable.
I would do the following: (1) research whether any of the rims in my
retired wheel collection have the same ERD and handedness, if so (2) I
would get about three beers, and (3) I would watch the World Cup and
unlace the wheel with the right rim and (4) swap it with the broken
rim. Alternately, I would just go buy a new rim that fit and build
that wheel. Reduce beer intake by one bottle. -- Jay Beattie.
yirgster
> Get three beers ...
Ah, some practical advice! Relevant too!
thirty-six
There is an obvious reason for failure, too much spoke tension. You
simply dont need to be anywhere near there. The ripping out of one
spoke will have reduced the tension in the others a little. If you
knock it down a little more when truing then I think the only problem
remaining is the possibility of the tyre (asssuming you are on covers)
splitting the damaged rim. So knock the tyre pressure down to the
lowest you can manage with. It wouldn't bother me too much for a
short period, I wouldn't use the brake there though.
Stephen Bauman
You did not mention the number of spokes or the type of rim. Both would
give some information regarding how much additional tension you had to
add to other spokes to get the wheel back to true and whether or not the
rim can take the additional tension.
Stephen Bauman
Tim McNamara
<3af052d1-4e13-46cb...@b35g2000yqi.googlegroups.com>,
yirgster <yirg....@gmail.com> wrote:
> Well, obviously, it's hard to venture an opinion without seeing the
> rim.
Easy opinion. It's toast. More spoke holes are going to fail. If
you're going to ride it, just do laps around the block.
--
That'll put marzipan in your pie plate, Bingo.
thirty-six
It can't, that's why it broke.
yirgster
Yes. Absolutely. This is a mavic ma3 with 32 (now 31) spokes. 8 years
old.
Here's a pic of the rim: http://img291.imageshack.us/img291/4964/20100624183649.jpg
yirgster
Yes, many spokes on the freewheel side are really tight. What are
"covers"?
kolldata
duck tape GOOD duck tape
or fiberglass-any resin and cloth handy ?
yirgster
Primarily I trued the wheel by loosening the spokes on the non-
freewheel side. Only one of which I felt too soft to do. I tightened
only very little on the freewheel side. Many of those spokes were
really tight. I wasn't much concerned about the offset of the rim.
kolldata
time to start a 'yirgster medical fund' ?
thirty-six
Wired tyres as opposed to tubulars.
thirty-six
I wouldn't much worry about it running true, more about it holding
together, I would knock off a half turn on all those spokes and then
more on the left side to clear the chainstay. Rub in a bit of
beeswax for any nipples that seem loose or pinch a bit of tape to
secure for the short period. You really shouldn't brake on that rim
so open out the caliper and take it easy.
thirty-six
> duck tape GOOD duck tape
> or fiberglass-any resin and cloth handy ?
Is that as good as newspaper and oil paint?
Peter Cole
> Well, obviously, it's hard to venture an opinion without seeing the
> rim.
>
> Riding uphill yesterday, a rear, freewheel side spoke pulled out of
> it's hole, ripping an elongated gap of nearly an inch on the
> underside, about 1/2" of one side of which very slightly extends just
> onto the angled portion of the rim wall (not the main nearly vertical
> wall).
>
> Didn't have any problems riding it a short distance to where my wife
> picked me up and last night I re-trued the wheel so it's reasonable.
> Actually, it's more true than many wheels I've seen. The rim seems
> strong to the hand. But, obviously, that's "seems", not "is".
>
> I've ordered another wheel but it won't be here to mid-next week and
> I've got to have my fix. (There are worse things to be addicted to. I
> hope.) So I'm wondering how safe it is to go out for short rides, even
> 8-10 miles, near the house. Would involve hills and descents since
> that's the topology. Getting home isn't the problem if there is a
> problem, but I don't think it would be too cool to have the rim
> collapse on me. I don't mind taking the downhills very, very slowly.
I wouldn't ride it. Being that it's an old rim, you don't know how much
sidewall you've got left, and that's about all that's keeping the rim
together.
> You know, in the old days (which I'm old enough to remember too well),
> you know, those days before indexed shifters and cassettes, in this
> situation you'd just swap rear wheels with an old one hanging around.
> Didn't matter what freewheel it was. Maybe I can re-commission one of
> my ancient bikes, in various stages of disrepair, cannibalized over
> the years, etc. But their gearing is definitely on the high side for
> me now, to say the least.
Even with indexing, a cluster with fewer sprockets can work well enough
with a little fiddling at least for a temporary fix.
MA-3's weren't known to be particularly reliable rims. Having spare
wheels (or at least rims) is convenient, especially if you like to run
different tires and/or can't tolerate downtime. Many bike components are
consumables (like rims), so it makes sense to keep an eye out for good
deals and pick up spare parts before things wear out. /end of sermonette.
thirty-six
> Even with indexing, a cluster with fewer sprockets can work well enough
> with a little fiddling at least for a temporary fix.
>
>
Yes, you should be able to chuck just about any wheel in there, just
dont expect to be able to shift more than a few sprockets accurately
(maybe as little as three). Just dial in the shifting in the middle
of the block.
Stephen Bauman
A picture is worth a thousand flames. :=)
I've no first hand experience with these rims. A web search reveals that
your experience with this rim is by no means unique. Maybe, it's mavic's
wear indicator in action. :=)
You've got two concerns riding the rim.
First, the rim will collapse under your weight due to missing structure.
The diagrams that I saw about this rim were not clear as to whether the
ferrules were attached at one or two points. If it was attached at only
one point, then it's fairly likely that the opposite wall of the hollow
box is still intact. That wall and the two side hollow boxes should
provide sufficient strength. It is a fairly heavy rim at 490 grams. I
would take some precautions. I'd cut down on tire pressure, avoid any
pavee and not carry heavy bricks on the rear carrier. There's no point in
over stressing an already damaged structure. OTOH, if two walls were torn
out or the weld was compromised, then I'd look to borrow a wheel for your
weekly fix.
Second, it's possible that other spokes are likely to go. Look carefully
around all the other spoke holes for small scratches or bulges. If you
find them, then a sprint for king of the mountains recognition on a club
ride will likely result in more spokes popping through the rim.
There's no reason you should not ride the wheel, if the only damage was
what appeared in your picture. You will be riding damaged goods and
should ride accordingly.
Good luck.
Stephen Bauman
Tim McNamara
Stephen Bauman <sba...@abt.net> wrote:
MA-3 rims have a single ferrule or eyelet, so it is only attached on the
face of the rim and not to the rim bed like the MA-2 was.
> Second, it's possible that other spokes are likely to go. Look
> carefully around all the other spoke holes for small scratches or
> bulges. If you find them, then a sprint for king of the mountains
> recognition on a club ride will likely result in more spokes popping
> through the rim.
Hard braking increases spoke tension much more than pedaling. A human
can't accelerate a bike anywhere near as hard pedaling as we can
decelerate it by braking. The mechanisms of spoke loading with rim
brakes versus pedaling is different as well.
mike.a...@gmail.com
> On Jun 24, 7:30 pm, Stephen Bauman <sbau...@abt.net> wrote:
>
> Yes. Absolutely. This is a mavic ma3 with 32 (now 31) spokes. 8 years
> old.
>
>
Note the hole is circular. There are no cracks leading to the next
hole. So it was not a classical overtighten rim, which tends to have
cracks around all the spokes pointing to the next spoke.
So, low pressure, low speed, avoid potholes, like everyone said.
Replace when you get your new wheel.
yirgster
> time to start a 'yirgster medical fund' ?
thanks everyone for your replies and info/analysis. It was
informative!!
Got to say the yirgster medical fund is a truly excellent and
compassionate idea. Thank you, kolldata for getting it off the ground!
Donations made easily via paypal and most appreciated!! Trust me. I'll
post a report of donations here everyday.
Michael Press
Tim McNamara <tim...@bitstream.net> wrote:
Not with rim brakes. Rim braking adds very little load.
Table 3 and Figure 9 in _The_Bicycle_Wheel_. The effect
of rim braking on a bicycle wheel is to slightly even
out the peak load, contrasted with radial point load alone.
> A human
> can't accelerate a bike anywhere near as hard pedaling as we can
> decelerate it by braking. The mechanisms of spoke loading with rim
> brakes versus pedaling is different as well.
--
Michael Press
thirty-six
> In article <timmcn-7679F8.12203025062...@news-1.mpls.iphouse.net>,
> Tim McNamara <tim...@bitstream.net> wrote:
>
>
>
> > In article <j_ydnXVIk7ELIbnRnZ2dnUVZ_jedn...@speakeasy.net>,
Bullshit, wheels break (as in fracture, not buckle) when braking.
yirgster
<mike.a.sch...@gmail.com> wrote:
> On Jun 24, 11:08 pm, yirgster <yirg.ke...@gmail.com> wrote:
>
> > On Jun 24, 7:30 pm, Stephen Bauman <sbau...@abt.net> wrote:
> <deleted>
>
> > Yes. Absolutely. This is a mavic ma3 with 32 (now 31) spokes. 8 years
> > old.
>
>
> Note the hole is circular. There are no cracks leading to the next
> hole. So it was not a classical overtighten rim, which tends to have
> cracks around all the spokes pointing to the next spoke.
>
> So, low pressure, low speed, avoid potholes, like everyone said.
> Replace when you get your new wheel.
Went out both friday and sat. Lowered the tire pressure, had to
center the rm by hand between the stays. There was a not too annoying
thump, thump, thump as I guess it's now out of round. Hardly used the
rear brake, didn't push up the hills at first. But as I gained
confidence in the wheel, justifiably or not, I started pushing more
and more, finally riding normally except wrt the rear brake and
descending more slowly. About 30 hilly miles. On Sat pumped tire to
100 lbs (still low for me) and rode normally, including pushing up the
hills but still descending more slowly and hardly using the rear
brake. About 40 miles. Wheel held up like a champ. New wheel arrives
tomorrow.
Thank you everyone for your help and thoughts!
Future: I'm going to follow jay's excellent suggestion of starting off
with three beers and then rebuild the wheel with my now spare campy
hub. Probably some cold day this winter. Tomorrow seems like a good
time to start with the beers though.
Peter Cole
> Went out both friday and sat. Lowered the tire pressure, had to
> center the rm by hand between the stays. There was a not too annoying
> thump, thump, thump as I guess it's now out of round. Hardly used the
> rear brake,
There's really no reason in normal riding to ever use the rear brake,
although, as others have pointed out, it has a negligible effect on
spoke tension.
> didn't push up the hills at first. But as I gained
> confidence in the wheel, justifiably or not, I started pushing more
> and more, finally riding normally except wrt the rear brake and
> descending more slowly. About 30 hilly miles. On Sat pumped tire to
> 100 lbs (still low for me) and rode normally, including pushing up the
> hills but still descending more slowly and hardly using the rear
> brake. About 40 miles. Wheel held up like a champ. New wheel arrives
> tomorrow.
Do yourself a favor and check out Sheldon Brown's article describing
stress relief of wheels (Jobst's technique).
thirty-six
Apparently the in joke which has been running for twenty years or so.
It's hilarious, look to the references for pixies and goblins.
(PeteCresswell)
>There's really no reason in normal riding to ever use the rear brake,
Maybe this is just a semantic issue around "normal riding", but I
find the rear brake essential in two situations:
- Loose gravel or otherwise slippery surfaces where the front
wheel will wash out under braking (which I experience with some
regularity)
- Failure of the front brake. (which I have not yet experienced,
although I've had a rear brake go South on me)
--
PeteCresswell
Frank Krygowski
- Descending, when you want to share the thermal load between two
wheels
- In emergency braking, when skidding of the rear wheel can be a
valuable indicator of impending pitchover
- When using the left hand to signal a turn during gentle braking
- When shifting between chainwheels during braking
- Frank Krygowski
Peter Cole
> Per Peter Cole:
>> There's really no reason in normal riding to ever use the rear brake,
>
> Maybe this is just a semantic issue around "normal riding", but I
> find the rear brake essential in two situations:
>
> - Loose gravel or otherwise slippery surfaces where the front
> wheel will wash out under braking (which I experience with some
> regularity)
True, you could also add alpine descents where two rims are better than
one for preventing blow off, or pulling heavy trailers preventing
jackknifing, but I wouldn't consider any of them "normal road riding. I
wasn't very enthusiastic about riding a rear rim with a big chunk
missing, much less so on gravel.
> - Failure of the front brake. (which I have not yet experienced,
> although I've had a rear brake go South on me)
Redundancy is a good idea, but that doesn't mean the brake is used, it
means it's there to be used. I didn't recommend the OP go without rear
brake, just that using it gently with a damaged rear wheel wasn't
necessary, since using it at all wasn't necessary. That, of course,
would change if his front cable snapped.
Jobst Brandt
>>> There's really no reason in normal riding to ever use the rear
>>> brake,
>> Maybe this is just a semantic issue around "normal riding", but I
>> find the rear brake essential in two situations:
>> - Loose gravel or otherwise slippery surfaces where the front wheel
>> will wash out under braking (which I experience with some
>> regularity)
What other kind of gravel is there besides "loose", other than being
the essence of asphalt paving and called pavement in the USA.
>> - Failure of the front brake. (which I have not yet experienced,
>> although I've had a rear brake go South on me)
I think this calls for details. What failed and how?
> - Descending, when you want to share the thermal load between two
> wheels
> - In emergency braking, when skidding of the rear wheel can be a
> valuable indicator of impending pitchover
Get off the old saws, "never brake in a turn and watch out for
pitchovers". Pitchover occurs not from braking force but when the
thighs strike the handlebars when the rider does not brace his body
weight with the hands:
http://www.sheldonbrown.com/brandt/over-the-bars.html
> - When using the left hand to signal a turn during gentle braking
Signal before a curve and brake in the curve with both brakes.
> - When shifting between chainwheels during braking:
That rings of more invalid physical imagery similar to "don't pick
your nose while braking".
Jobst Brandt
David Scheidt
:Frank Krygowski wrote:
:>>> There's really no reason in normal riding to ever use the rear
:>>> brake,
:>> Maybe this is just a semantic issue around "normal riding", but I
:>> find the rear brake essential in two situations:
:>> - Loose gravel or otherwise slippery surfaces where the front wheel
:>> will wash out under braking (which I experience with some
:>> regularity)
:What other kind of gravel is there besides "loose", other than being
:the essence of asphalt paving and called pavement in the USA.
Good quality crushed aggregate, properly screened, properly applied,
properly graded, properly compacted, and properly maintained makes a
rock-hard surface that will support maximum breaking loads from a
bicycle. It's not smooth enough for proper cornering, but it doesn't
move under the wheels. Few gravel roads meet these (particularly the
"properly maintained" one), but they do exist.
--
There's a rather large difference between pissing on a 600V third rail
and a 33 kV power line.
(PeteCresswell)
>>> - Failure of the front brake. (which I have not yet experienced,
>>> although I've had a rear brake go South on me)
>
>I think this calls for details. What failed and how?
Oil seal failed in the internally-geared hub - dripping on to the
rotor. Discovered while descending rocky slope littered with
abovementioned loose gravel..... an "interesting" experience.
I've also had my (open? closed?) system Hope slowly lock up on
the front wheel descending a steep slope at walking pace. Had to
sit that one out until things cooled down... maybe 15 minutes.
--
PeteCresswell
Frank Krygowski
> Frank Krygowski wrote:
> >>> There's really no reason in normal riding to ever use the rear
> >>> brake,
> >> Maybe this is just a semantic issue around "normal riding", but I
> >> find the rear brake essential in two situations:
> >> - Loose gravel or otherwise slippery surfaces where the front wheel
> >> will wash out under braking (which I experience with some
> >> regularity)
>
> What other kind of gravel is there besides "loose", other than being
> the essence of asphalt paving and called pavement in the USA.
Jobst, if you're going to get picky about things like possible minor
redundancies, please get picky with yourself about replies and
attributions. I did not write the sentence to which you responded.
Count chevrons and leave the correct attribution in place.
>
> >> - Failure of the front brake. (which I have not yet experienced,
> >> although I've had a rear brake go South on me)
>
> I think this calls for details. What failed and how?
>
> > - Descending, when you want to share the thermal load between two
> > wheels
> > - In emergency braking, when skidding of the rear wheel can be a
> > valuable indicator of impending pitchover
>
> Get off the old saws, "never brake in a turn and watch out for
> pitchovers".
Get off the misrepresentations. I did not say "never brake in a
turn."
> Pitchover occurs not from braking force but when the
> thighs strike the handlebars when the rider does not brace his body
> weight with the hands:
Fine. I haven't - and won't - test the ultimate reason for pitchover,
so I'm not going to challenge your vision of the mechanics. Still, I
find skidding of the rear wheel to be a useful warning in maximum
braking situations. YMMV.
> > - When using the left hand to signal a turn during gentle braking
>
> Signal before a curve and brake in the curve with both brakes.
I signal to communicate with other road users. The details of the
desired communication vary with the situation. At times, I find it
valuable to signal while maintaining braking with the rear wheel.
Sorry, but I won't let Jobstian commands interfere with my judgment on
these matters.
(Does _anybody_ ever say "Hmm, will, Jobst say I shouldn't signal
now?" ;-)
> > - When shifting between chainwheels during braking:
>
> That rings of more invalid physical imagery similar to "don't pick
> your nose while braking".
What a snotty thing to say!
- Frank Krygowski
Jobst Brandt
>>>> Failure of the front brake. (which I have not yet experienced,
>>>> although I've had a rear brake go South on me)
>> I think this calls for details. What failed and how?
> Oil seal failed in the internally-geared hub - dripping on to the
> rotor. Discovered while descending rocky slope littered with
> above mentioned loose gravel..... an "interesting" experience.
More mystery. How did the failing oil seal make the brake fail and
what does it have to do with the internal gears? Are you saying the
oil made the brake shoes glide freely on a disk brake?
> I've also had my (open? closed?) system Hope slowly lock up on
> the front wheel descending a steep slope at walking pace. Had to
> sit that one out until things cooled down... maybe 15 minutes.
Are you attributing brake failure to braking heat? Please be more
specific for those who weren't there.
Jobst Brandt
mike.a...@gmail.com
> Pete Cresswell wrote:
<deleted>
> > I've also had my (open? closed?) system Hope slowly lock up on
> > the front wheel descending a steep slope at walking pace. Had to
> > sit that one out until things cooled down... maybe 15 minutes.
>
> Are you attributing brake failure to braking heat? Please be more
> specific for those who weren't there.
>
> Jobst Brandt
? Disc brake pad heated by braking also heated the hydralic fluid
until it expanded and locked the brake pad to the disc brake?
Jobst Brandt
>>> I've also had my (open? closed?) system Hope slowly lock up on the
>>> front wheel descending a steep slope at walking pace. Had to sit
>>> that one out until things cooled down... maybe 15 minutes.
>> Are you attributing brake failure to braking heat? Please be more
>> specific for those who weren't there.
> Disc brake pad heated by braking also heated the hydraulic fluid
> until it expanded and locked the brake pad to the disc brake?
You must be using poor brake fluid. Automotive fluid never does that
even though the brake pads do not retract from their disks while
getting much hotter than bicycle disks. Get in touch with your brake
and fix that amount of braking you need. There are many disk brakes
that have much heat that work. Even rim berry shoe brakes work fine
while in long time the tire may release from rim in a bang.
Jobst Brandt
AMuzi
> Frank Krygowski wrote:
>
>>>> There's really no reason in normal riding to ever use the rear
>>>> brake,
>
>>> Maybe this is just a semantic issue around "normal riding", but I
>>> find the rear brake essential in two situations:
>
>>> - Loose gravel or otherwise slippery surfaces where the front wheel
>
> What other kind of gravel is there besides "loose", other than being
> the essence of asphalt paving and called pavement in the USA.
>
>>> - Failure of the front brake. (which I have not yet experienced,
>
> I think this calls for details. What failed and how?
>
>> - Descending, when you want to share the thermal load between two
>> wheels
>
>> - In emergency braking, when skidding of the rear wheel can be a
>> valuable indicator of impending pitchover
>
> Get off the old saws, "never brake in a turn and watch out for
> pitchovers". Pitchover occurs not from braking force but when the
> thighs strike the handlebars when the rider does not brace his body
> weight with the hands:
>
> http://www.sheldonbrown.com/brandt/over-the-bars.html
>
>> - When using the left hand to signal a turn during gentle braking
>
> Signal before a curve and brake in the curve with both brakes.
>
>> - When shifting between chainwheels during braking:
>
> That rings of more invalid physical imagery similar to "don't pick
> your nose while braking".
or when trying to lead Italy:
http://www.youtube.com/watch?v=mApFJ2g-Gd4
(not that Italians would follow anyway)
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
thirty-six
Brake fluid is known to be hygroscopic when deterioration has occured
through oxidation, usually due to rubber hoses. There is a water
content in the brake fluid, and this boils at a relatively low
temperature so holding on the pads. There should be a release valve
which depressurises the master cylinder when the lever is released,
but poor servicing could easily see this blocked or jammed (if it
actually exists or performs when new).
(PeteCresswell)
>? Disc brake pad heated by braking also heated the hydralic fluid
>until it expanded and locked the brake pad to the disc brake?
That was my interpretation.
--
PeteCresswell
David Scheidt
:Mike Schwab wrote:
:>>> I've also had my (open? closed?) system Hope slowly lock up on the
:>>> front wheel descending a steep slope at walking pace. Had to sit
:>>> that one out until things cooled down... maybe 15 minutes.
:>> Are you attributing brake failure to braking heat? Please be more
:>> specific for those who weren't there.
:> Disc brake pad heated by braking also heated the hydraulic fluid
:> until it expanded and locked the brake pad to the disc brake?
:You must be using poor brake fluid. Automotive fluid never does that
:even though the brake pads do not retract from their disks while
:getting much hotter than bicycle disks. Get in touch with your brake
Sure it does. A fairly common failure of brake hoses is they fail to
return fluid from the calipers to the master cylinder, which is
required for the brakes to release. (Typically the failure is not
complete; the rate at which fluid leaves the calipers is just greatly
reduced.) Heat transfer aggrevates the problem, and can lead to
locked wheels. fluid can get into the brake calipers when this
happens because it's forced under high pressure.
--
sig 104