Carbon fiber spokes + Alloy Rim = DISASTER(for MAVIC users)

Discuss light weight issues concerning road bikes & parts.
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Lelandjt
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by Lelandjt

You guys are responding to this as if this isn't a known problem. Remember when Mavic recalled these wheels for the same issue? They said they have new spokes and the problem's fixed but I'm not surprised to see it still exist. Rigid carbon spokes (as opposed to Spinergy's PBO spokes) are a no no. Sapim tried it and just couldn't get them to work.

by Weenie


wingguy
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Joined: Thu Mar 08, 2012 11:43 pm

by wingguy

Lelandjt wrote:You guys are responding to this as if this isn't a known problem. Remember when Mavic recalled these wheels for the same issue? They said they have new spokes and the problem's fixed but I'm not surprised to see it still exist.

But that's the thing, isn't it? When there was a problem with the first gen spokes Mavic recalled the wheels after a season. The redesigned spokes have been out on R-Sys, Ksyrium SLRs and other wheels for a further 9 years without any recall (our shop alone has probably sold 20 to 30 TraComp equipped wheels per season since then and haven't had any problems). It just doesn't make sense that there is still a known, recurring issue with TraComp spokes that Mavic have simply ignored since 2009.

Certainly not one bad enough to make it remotely likely that the same group of riders would have two failures one after the other with no external factors.

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kgt
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Location: Athens, Greece

by kgt

ohhyeok90 wrote:
kgt wrote:I may be wrong but the third photo of the first post looks like photoshop to me. Even the size of the rear wheel seems huge.


That's what 'Perspective' is.


Believe me, I know exactly how perspective works...

whosatthewheel
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by whosatthewheel

certainly they have very tall guard rails... or very small bikes

nemeseri
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by nemeseri

kgt wrote:Sorry, I don't believe that. Maybe extreme bad luck in your case but, no, Mavic wheels do not collapse like that. Not even no name chinese crapy wheels snap like that.


Don't you think that it's plausible even after the velonews article? Velonews reported a very similar failure with the post-recall wheels and I can imagine that mavic might have fixed the problem and then somehow the issue resurfaced again a few years later.

Also accusing somebody with photoshopping the images? Why would he do that?

antonioiglesius
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Joined: Sat Oct 15, 2016 9:08 pm

by antonioiglesius

I did a Google image search, here's the original blog (you can Google translate it), it looked like a pretty awesome organized ride (at least until the wheel failed):
http://blog.naver.com/PostView.nhn?blog ... 1109870059

The guard rails look correctly proportioned based on this image screen captured from the blog:

Image

So.... does it have to do with wheel tensions? I'm just curious... If the two guys bought their wheels from the same retailer, who has a mechanic who does things wrong, then someone needs to tell him/her.

jwfinesse
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Location: NY

by jwfinesse

i’ll translate some of the important facts

rider weight 63kg
rim trued within acceptable tolerance
freehub oiled periodically
no indication of spokes being loose (the blogger states ticking noise from the spokes would come prior to this kind of catastrophic failure)
no potholes, manhole covers, or otherwise indicating imperfect road
not a curve, but a straight downhill
no cars around
crashed alone (not a pile-up with other riders)
the frame, components, and everything else still looks the same as prior to crash.

he also states that doesn’t know whether the sudden deformation of the rim caused the accident, or the act of falling down bent the rim. He felt a serious wobble at the rear wheel just before he surged forward.

His tone is not blaming anyone, but rather he is glad that he walked out without serious injuries.



I doubt OP has a dog in this truth vs bs fight. The blogger’s domain, Naver, is notorious for taking down posts if they even smell a whiff of legal actions, which means Mavic Korea felt the pics are real, thus pressing no legal actions for more than a month after the Oct 2nd post. And it usually takes only a day or two. i still have and write stuff on Naver blog, so I know how quickly shit works over there.

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TarugoKing
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by TarugoKing

kgt wrote:
ohhyeok90 wrote:
kgt wrote:I may be wrong but the third photo of the first post looks like photoshop to me. Even the size of the rear wheel seems huge.


That's what 'Perspective' is.


Believe me, I know exactly how perspective works...


Does not look like PS. This type of distortion is pretty common with smart phone cameras. You would notice this on some of your pictures as well. They are pretty common especially on the corners.

Slack
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Joined: Fri Dec 27, 2013 11:37 pm

by Slack

jwfinesse wrote:i’ll translate some of the important facts

rider weight 63kg
rim trued within acceptable tolerance
freehub oiled periodically
no indication of spokes being loose (the blogger states ticking noise from the spokes would come prior to this kind of catastrophic failure)
no potholes, manhole covers, or otherwise indicating imperfect road
not a curve, but a straight downhill
no cars around
crashed alone (not a pile-up with other riders)
the frame, components, and everything else still looks the same as prior to crash.

he also states that doesn’t know whether the sudden deformation of the rim caused the accident, or the act of falling down bent the rim. He felt a serious wobble at the rear wheel just before he surged forward.

His tone is not blaming anyone, but rather he is glad that he walked out without serious injuries.



I doubt OP has a dog in this truth vs bs fight. The blogger’s domain, Naver, is notorious for taking down posts if they even smell a whiff of legal actions, which means Mavic Korea felt the pics are real, thus pressing no legal actions for more than a month after the Oct 2nd post. And it usually takes only a day or two. i still have and write stuff on Naver blog, so I know how quickly shit works over there.


It could well have come down to how those wheels were trued in that case, the tracomp spokes are not meant to be run with much tension/if any tension as they do not have any stretch in them as a steel spoke would. If both wheels were trued by the same shop it could well be a case of a mechanic or shop staff that is inexperienced with the product. I work for a retailer that is in the same region as Winguy and we sell in excess of 200 pairs of mavic wheels a year and have never seen a failure like this in the time that I have been working there.

jwfinesse
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Joined: Wed Oct 24, 2012 4:51 am
Location: NY

by jwfinesse

i should have written it more clearly

i shloudve written the wheel was round and straight wihtin tolerance. he never states whether his wheels were actually trued or not.

ohhyeok90
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Joined: Sun Nov 08, 2015 2:24 am

by ohhyeok90

BH rider and Focus rider live about 400km away. yet I can't 100% sure, but highly unlikely two wheels trued at the same bike shop(person).

plus, I can't sure whether the wheels trued properly or not. but despite of shallow brake tolerence there is no brake rub or something, it means you can't tell it is wrong by eyes(without tension meter).

In this case, if the cause were bad truing, that is the problem also. how can mavic users trust thier wheels and ride then? every time they ride, they check each spoke with tension meter?

youngs_modulus
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Location: Portland, OR USA

by youngs_modulus

joejack951 wrote:Given how folded those aluminum rims are, if these failures are real they appear to be the result of improperly heat treated aluminum, or aluminum that has not been heat treated at all (T0 condition, straight off the extruder). 6000 or 7000 series aluminum in the T6 condition will not deform anywhere near that much without cracking in my experience both fabricating with the metal and with bicycle rims.


Looking at the photos, you may be onto something here. That's a lot of plastic deformation. Mavic rims are probably made from an alloy very much like 6061. In its usual, T6 condition, its elongation at failure is only 12%. In T0 condition, elongation is 25%, which is basically bubble gum for metals. But T0 is really, really weak.

I can't help wondering if Mavic built up some rims that had only been heat-treated to T4 condition with an elongation at failure of around 22%. It's a lot stronger than T0 (but weaker than T6) and that would explain how that rim folded sideways without breaking.

I also agree with people who suggest that this failure may be the result, not the cause, of the crash. Regardless of the heat treatment, that wheel took a large, abrupt side load. If the rim wasn't properly heat treated, a sideways skid that got caught suddenly (a high side, in motorcycle parlance) could definitely have caused that failure. Something happened, and it really doesn't look like the spokes had much to do with it.

As many people here know, the bike industry has to deal with riders who experience JRA failures. JRA stands for "just riding along," which is what the rider was always doing immediately before the part failed. The term is also a useful reminder that forks don't randomly bend backwards and wheels don't randomly fold over. The proximate cause is almost always something physical that happened at the time of failure or shortly before.

I don't mean to say the poor rider who crashed is lying. I'm just saying that when you're taken by surprise, it can be hard to determine whether your bike slewed to one side because your wheel bent or whether your wheel bent because your bike slewed to one side.

Diagnosing failure over the internet is always dangerous, but that wheel looks like it had stopped turning when it bent. It may have been too easily (wrong heat treatment) and it may legitimately not have been the rider's fault.

If Mavic had a run of mis-heat-treated wheels, they'd probably know about it. That's a big mistake. You can check the heat treatment of 6061 by measuring thermal conductivity. 6061-T0 has a higher thermal conductivity (184 W/m^2/K) than 6061-T6 (167 W/m^2/K) or 6061-T4 (154 W/m^2/K).

youngs_modulus
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Location: Portland, OR USA

by youngs_modulus

Quick question: was the Focus rider's rear brake massively off-center after the crash? If it wasn't, that might be a sign that the crash was already underway when the wheel collapsed. Again, I'm not accusing anyone of lying; it can be hard to get the sequence of events right in situations like this.

glepore
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Location: Virginia USA

by glepore

youngs_modulus wrote:
joejack951 wrote:Given how folded those aluminum rims are, if these failures are real they appear to be the result of improperly heat treated aluminum, or aluminum that has not been heat treated at all (T0 condition, straight off the extruder). 6000 or 7000 series aluminum in the T6 condition will not deform anywhere near that much without cracking in my experience both fabricating with the metal and with bicycle rims.


Looking at the photos, you may be onto something here. That's a lot of plastic deformation. Mavic rims are probably made from an alloy very much like 6061. In its usual, T6 condition, its elongation at failure is only 12%. In T0 condition, elongation is 25%, which is basically bubble gum for metals. But T0 is really, really weak.

I can't help wondering if Mavic built up some rims that had only been heat-treated to T4 condition with an elongation at failure of around 22%. It's a lot stronger than T0 (but weaker than T6) and that would explain how that rim folded sideways without breaking.

I also agree with people who suggest that this failure may be the result, not the cause, of the crash. Regardless of the heat treatment, that wheel took a large, abrupt side load. If the rim wasn't properly heat treated, a sideways skid that got caught suddenly (a high side, in motorcycle parlance) could definitely have caused that failure. Something happened, and it really doesn't look like the spokes had much to do with it.

As many people here know, the bike industry has to deal with riders who experience JRA failures. JRA stands for "just riding along," which is what the rider was always doing immediately before the part failed. The term is also a useful reminder that forks don't randomly bend backwards and wheels don't randomly fold over. The proximate cause is almost always something physical that happened at the time of failure or shortly before.

I don't mean to say the poor rider who crashed is lying. I'm just saying that when you're taken by surprise, it can be hard to determine whether your bike slewed to one side because your wheel bent or whether your wheel bent because your bike slewed to one side.

Diagnosing failure over the internet is always dangerous, but that wheel looks like it had stopped turning when it bent. It may have been too easily (wrong heat treatment) and it may legitimately not have been the rider's fault.

If Mavic had a run of mis-heat-treated wheels, they'd probably know about it. That's a big mistake. You can check the heat treatment of 6061 by measuring thermal conductivity. 6061-T0 has a higher thermal conductivity (184 W/m^2/K) than 6061-T6 (167 W/m^2/K) or 6061-T4 (154 W/m^2/K).

This finally is a well reasoned reply.


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by Weenie


ohhyeok90
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Joined: Sun Nov 08, 2015 2:24 am

by ohhyeok90

youngs_modulus wrote:Quick question: was the Focus rider's rear brake massively off-center after the crash? If it wasn't, that might be a sign that the crash was already underway when the wheel collapsed. Again, I'm not accusing anyone of lying; it can be hard to get the sequence of events right in situations like this.


Yes, unlike BH rider case, Focus rider's wheel could folded after crash.
(and in my opinion even though there is crash, rim folded like that has significant problem. because crash itself isn't that huge.)

and it was a month ago, so I can't assure you about brake center.

but, crash because of rear wheel wobble. and I doubt rim or carbon spokes.
You can see this from case of BH rider's R-sys rim. MAVIC ALLOY RIM CAN FOLD.

(of course sometimes rear wobble happens due to stucked mavic's outdated hub(not instant 360). hot bushing problem as far as i know. but most of these are cause of poor maintence like forgot put oil.)

and I have question. If you have mavic wheel which has made by same factory and same process, would you using it?

it is my biggest concern. my friends still using same model and probably same condition because it is possible they import my contry and you know...
I just don't want to watch them hurt anymore.

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