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Old 01-24-12, 07:21 PM   #1
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What's wrong with this Mavic?

Aside from it almost killing me today. This Mavic m40 wheel self-destructed when I braked hard to avoid an old lady. Seriously. I'm still having flashbacks.

Is there a relation between those uneven brake burns and the catastrophic failure I experienced? I'm puzzled, seemed fine when I trued a few weeks ago. There was no impact and I regularly bounced off curbs with it. Can hard braking distort rims? Was it the momentum vs. the vise-like dual pivot 105s? What's going on with those spokes that would cause those patterns?

Had to carry the bike 1/4 mile to get back to the street and call a cab. Good thing it was the 22lbs Centurion and not one of my other beasties.



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Old 01-24-12, 07:53 PM   #2
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I would be suspicious that the spoke tension was severly overtightened to pretzel like that from braking.
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Old 01-24-12, 07:55 PM   #3
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How many miles have you ridden the rim? Had you been experiencing brake shudder recently? I had a wheel catastrophically fail on me because the braking surface had gotten so thin that the air pressure on a hot day caused the tube to blow out the rim. Thankfully, I wasn't riding it at the time.
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Old 01-24-12, 08:00 PM   #4
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I had a well-loved MA40 where the brake surface eventually wore through. As mentioned, maybe it was getting thin to the point of losing structrual integrity. Creck the braking surface for hairline cracks.
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Old 01-24-12, 09:58 PM   #5
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I would be suspicious that the spoke tension was severly overtightened to pretzel like that from braking.
I've built a few wheels (lots of amateur tension), but nothing like this. I thought tight is good as long as it's even, I mean it's got to support a lot more than spoke tension. I know wheels don't like lateral stress, but radial stress shouldn't cause it to pretzel. Don't see any broken spokes, and checking for wear now, but still puzzled why the spokes cause the rim to swell around the holes. Just saw another MA40 with similar brake wear on the rim... is this normal?
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Old 01-24-12, 10:01 PM   #6
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... I regularly bounced off curbs with it.
You may have answered your own question.
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Old 01-24-12, 10:05 PM   #7
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You may have answered your own question.
+1
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Old 01-24-12, 10:08 PM   #8
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You dont see those compression bulges in the rim sidewall much,
since double eyelet rims are Not 'the norm', anymore..
a single eyelet rim does not do that..

seems evident, by now, the rim was not the issue , the riders traffic interaction
and treatment before hand may be.

Mavic has not made those rims in a very long time, and accidents happen.

Sheesh

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Old 01-24-12, 11:03 PM   #9
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You may have answered your own question.
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You dont see those compression bulges in the rim sidewall much,
since double eyelet rims are Not 'the norm', anymore..
a single eyelet rim does not do that..

seems evident, by now, the rim was not the issue , the riders traffic interaction
and treatment before hand may be.

Mavic has not made those rims in a very long time, and accidents happen.

Sheesh
Oh, come on, I've bunny hopped over train tracks with 27" Weinmanns; vintage double walls hold up perfectly fine. That's a lot more stress than a 4 " curb. That said, I think the wheel was poorly trued and the wear on the rim may have contributed. What traffic interaction? All I did was brake, albeit, hard.

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Old 01-26-12, 11:09 PM   #10
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Turns out half the eyelets were rusted out under the rim tape. That would certainly cause hard braking to destroy the rim. Bought it used but never checked beneath the tape. Lesson learned the hard way, thank god no one got hurt! Flea f%^'n Bay indeed.


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Old 01-26-12, 11:41 PM   #11
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That's just one of the downsides to vintage parts. I'm assuming the seller probably wasn't aware of the problem either.
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Old 01-27-12, 05:59 AM   #12
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I would be suspicious that the spoke tension was severly overtightened to pretzel like that from braking.
+1

Take a look at the areas where there is uneven wear and you find a spoke. This is indicative of uneven spoke tensions and overtightening.
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Old 01-27-12, 07:03 AM   #13
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im on this train, overtightened my arc en ciel's and they got some chattery brake surface all of a sudden,
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Old 01-27-12, 07:07 AM   #14
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My next-door neighbor used to keep his spokes super tight. Then one day he discovered stress cracks running between some of the spoke holes. Time to string new wheels...
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Old 01-27-12, 07:10 AM   #15
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+1

Take a look at the areas where there is uneven wear and you find a spoke. This is indicative of uneven spoke tensions and overtightening.
NO. NO. NO.

That was the norm back in the day.
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Old 01-27-12, 07:15 AM   #16
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I've built a few wheels (lots of amateur tension), but nothing like this. I thought tight is good as long as it's even, I mean it's got to support a lot more than spoke tension. I know wheels don't like lateral stress, but radial stress shouldn't cause it to pretzel. Don't see any broken spokes, and checking for wear now, but still puzzled why the spokes cause the rim to swell around the holes. Just saw another MA40 with similar brake wear on the rim... is this normal?
Guess you know why now?
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Old 01-27-12, 07:21 AM   #17
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NO. NO. NO.

That was the norm back in the day.

Agreed.
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Old 01-27-12, 07:28 AM   #18
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NO. NO. NO.

That was the norm back in the day.
So you don't think this wheel shows indications of uneven and overtightened spokes...

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Having built close to 1000 wheelsets over the past 40 years, I beg to differ.....

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Old 01-27-12, 10:03 AM   #19
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So you don't think this wheel shows indications of uneven and overtightened spokes...

Having built close to 1000 wheelsets over the past 40 years, I beg to differ.....
I'm about 2,000 wheelsets up on you so.....

The sidewall marks have nothing to do with the wheel being over-tensioned, marks like that are/were very normal for properly tensioned wheels back in the day. Could the OP's wheel have failed due to over-tension? Yes, absolutely. But then again he 'bounced off of curbs' so who knows.

And a majority of the time cracking eyelets has nothing to do with over-tensioning.
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Old 01-27-12, 10:17 AM   #20
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The sidewall marks have nothing to do with the wheel being over-tensioned, marks like that are/were very normal for properly tensioned wheels back in the day.
+1 All rims wear this way, it's just more apparent on rims with anodized sidewalls.

The failed wheel could very well be from being improperly built or from user abuse. But, to conclude that it was improperly built or improperly tensioned from the wear on the rims is, I belive, incorrect.
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Old 01-27-12, 10:19 AM   #21
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Notice how the spoke threads are protruding from the bottom of the nipple. Could this indicate that the spokes used were too long and they ran out of threads before achieving adequate tension? It indicates to me an inexperienced wheel builder (if you believe every online wheelbuilding book). I've only built 4, I have no room to talk, but I'm curious.
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Old 01-27-12, 10:48 AM   #22
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Notice how the spoke threads are protruding from the bottom of the nipple. Could this indicate that the spokes used were too long and they ran out of threads before achieving adequate tension? It indicates to me an inexperienced wheel builder (if you believe every online wheelbuilding book). I've only built 4, I have no room to talk, but I'm curious.
Yes, but in this particular instance probably not.
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Old 01-27-12, 11:28 AM   #23
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Thanks all for the useful/interesting input. AFAICT, it had everything to do with the eyelets rusting out and breaking off, not so much the spoke tension or the uneven wear on the rim. And please, not "rider abuse", wheels aren't that frail. I've ridden plenty of miles on broken spokes, it's not always catastrophic.

I agree with miamijim, I've seen uneven wear on older ano rims (where they're more conspicuous). As for tension, I'm sure there are engineering specs, but I just try to keep them even and "pling" tight. Whatever is going on should be apparent during truing and prestress, not when you hit a bump or wail on the brakes.

So this all jives, pressure and kinetic energy on wheel > distortion > spoke failure at the rim eyelets due to corrosion > collapse. What happened was unusual, there was no rust on the spokes so they all turned fine (below). Just didn't occur to me that the flanges on the eyelets were mostly kaput!


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Old 01-27-12, 12:19 PM   #24
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Quote:
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I'm about 2,000 wheelsets up on you so.....

The sidewall marks have nothing to do with the wheel being over-tensioned, marks like that are/were very normal for properly tensioned wheels back in the day. Could the OP's wheel have failed due to over-tension? Yes, absolutely. But then again he 'bounced off of curbs' so who knows.

And a majority of the time cracking eyelets has nothing to do with over-tensioning.
I don't see any cracked eyelets in the images just rust, but we are only seeing a small section and only one side. The only definitive way to know is to have the wheel in hand so you could compare the wear side-to-side, but having it taco right after it was trued speaks volumes about the overtensioning. I use to climb concrete staircases with 26" MA-40s and 1.95" tires and I never had one fail. The abuse here was not rider abuse, it was poor build and maintenance

Also, the regular wear only appears where the spoke are so uneven anodizing is unlikely to be at fault, but the excessive thread exposure and regular wear only at the spokes sure indicates that the rim was deformed in those locations due to overtightening. Early anodized wheel tended to develop irregular wear as the result of differences in the hardness of the anodizing, but this very regular pattern, which only appears at each spoke location, indicates overtensioning to me. Just a poor wheelbuilding job followed up by poor retensioning.....

Either way, without the wheel in hand we are both just giving our best guess.
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Old 01-27-12, 02:51 PM   #25
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Walk back to the street from where? Perhaps the terrain where you were riding has more to do with the wheel than the sudden stop.

the only yime I have ever seen a wheel sustain damage from a sudden stop was the result of hitting something and or crashing.

I think you might notice other issues with a fatigued sidewall before it was weak enough to allow the wheel to taco from a sudden stop.
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