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

Discuss light weight issues concerning road bikes & parts.
alcatraz
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Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

joejack951 made a good observation I think.

I vote crap rims...

/a

ohhyeok90
Posts: 48
Joined: Sun Nov 08, 2015 2:24 am

by ohhyeok90

UPDATE

yesterday morning, Amer Sports Korea(http://www.amerkorea.com/) contact BH rider by e-mail and afternoon, they spoke each other via phone.
and I heard this from BH rider's wife.

"First of all, it's hard to determine exactly what's causing the crash, but I'm sorry it happened while using our wheelset. and we would like to offer compensation for damage through discussion."

by Weenie


youngs_modulus
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Location: Madison, WI USA

by youngs_modulus

Good news! And I’d say that’s not just corporate-speak. If they have the same info we do, it really is hard to determine what caused the crash. I’m glad the Korean distributor is doing the right thing.

whosatthewheel
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by whosatthewheel

Just to clear the air about tracomp and R-SYS. There is hardly any tension at all on those spokes... these wheels don't operate like a classic "steel spokes" wheel in tension. The spokes are tensioned and compressed at each wheel revolution. The spokes are rigid and can tolerate quite a lot of vertical load.

The only way the wheel can collapse is either due to impact... could even just be a cat crossing your path or by hub failure, which does not appear to be the case here.

The rear is a bit more complicated, as only half the spokes are tracomp, the rest are alloy spokes in tension, I believe

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kgt
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by kgt

TarugoKing wrote: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.

I keep looking at the exploded rear wheel of the Focus in comparison to the front wheel of the bike behind it (the one with the black-red tire). The image does not look normal to me unless the camera of the phone has some really strange distortion.
Sure, I may be wrong but that photo does not convince me. Anyway, I will not insist...

GothicCastle
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Joined: Mon Jul 04, 2016 1:52 am

by GothicCastle

Very difficult to do forensics over the internet with a few photos.

ohhyeok90 wrote:checking spokes tension and hubs regularly.


I would guess this had something to do with it. Someone unfamiliar with the wheels improperly tensioning them over time. The rim failure is more consistent with impact than spoke failure. The impact did not necessarily happen on this ride.

KLabs
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by KLabs

GothicCastle wrote:Very difficult to do forensics over the internet with a few photos.

ohhyeok90 wrote:checking spokes tension and hubs regularly.


I would guess this had something to do with it. Someone unfamiliar with the wheels improperly tensioning them over time. The rim failure is more consistent with impact than spoke failure. The impact did not necessarily happen on this ride.


It looks like the rims collapsed during the compression portion/cycle of the wheels rotation and the rim skewed sideways until it failed. This would mean that the spokes were under tensioned, allowing the rim to skew sideways under compression. If the spokes were under tensioned, the rider would only need to be in an off axis position on the bike to encourage the rim to skew sideways. Both of these situations occurred at speed, downhill, and perhaps rider position at the time of the failure is important.

I initially thought that the spokes might be over tensioned but the pics, to me, seem to me to be saying under tensioned.

youngs_modulus
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Location: Madison, WI USA

by youngs_modulus

I follow your reasoning, I think. But the rim didn't just buckle (skew sideways until it failed) from compression; it got hit hard from the side. It may also have been much weaker than normal due to improper heat treatment; we don't know.

Even a rim with no spokes can support your full weight without buckling. Try sitting on one sometime. Old box-section rims flex into ellipses, but they spring back when you stand up. My Kinlin 30-mm deep aluminum rims are quite firm, simply from the additional depth (sectional modulus). 60-mm-deep carbon rims are way, way stiffer in the radial direction than a box-section aluminum rim.

Antoine
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Location: France

by Antoine

Could the rim strengh have been affected by excessive heat (or cold) during storage ?

Nice to see that cycling is popular in south Korea, but looking at the pictures I see many bikes lying on the ground, wich means people in Korea are not experienced enough and a bit careless with bikes.
So it could be an error from the mechanic like applying incorrect spoke tension or an error from the owner (like leaving the bike in his car in high temperatures).
I don't know where the rims are made and the wheels built (hopefully still in France), but those wheels may also have suffered during storage and transportation. I wonder where the Korean distributor is buying Mavic stuff, maybe not directly from France.

And I don't think south Korean would be lying on anything.

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

by ohhyeok90

Antoine wrote:Could the rim strengh have been affected by excessive heat (or cold) during storage ?

Nice to see that cycling is popular in south Korea, but looking at the pictures I see many bikes lying on the ground, wich means people in Korea are not experienced enough and a bit careless with bikes.
So it could be an error from the mechanic like applying incorrect spoke tension or an error from the owner (like leaving the bike in his car in high temperatures).
I don't know where the rims are made and the wheels built (hopefully still in France), but those wheels may also have suffered during storage and transportation. I wonder where the Korean distributor is buying Mavic stuff, maybe not directly from France.

And I don't think south Korean would be lying on anything.


I heard French have brilliant logical mind due to Baccalaureate or something.
But you don't seem like. and I won't judge all the french by only one of you.
saw couples of photo and saying "Korea are not experienced enough and a bit careless with bikes."
it calls 'hasty generalization'.
and also, bike and people who carring it are in the same temp. while moving.

BTW, Mavic was sold to Amer Sports which is Finland company, so I don't blame you french.

mattr
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by mattr

Antoine wrote:Could the rim strength have been affected by excessive heat (or cold) during storage ?
No. Not even if it was a composite rim.

Antoine wrote:Nice to see that cycling is popular in south Korea, but looking at the pictures I see many bikes lying on the ground, wich means people in Korea are not experienced enough and a bit careless with bikes.
Nice generalisation (or not). And FWIW I've seen people lying bikes on the floor in Scotland, and they invented the bike.......

ohhyeok90
Posts: 48
Joined: Sun Nov 08, 2015 2:24 am

by ohhyeok90

UPDATE

This is URL of Focus Rider's blog, 'A conversation with Mavic personnel related to the compensation of folded 125 rear wheel'
http://blog.naver.com/kimmc1403/221141701914

They promise give him new Ksyrium SLR rear.(and also consider front one not decided yet).
and paid medical expenses and damaged clothes will be compensated.
but they still can't explain why this is happening.

for those who want more info...
https://translate.google.com/#ko/en

Antoine
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Location: France

by Antoine

Good news, seems like service is good in South Korea or they are responsible somewhat. Mavic France wouldn't have done anything.

I was thinking South Korea is pretty new in cycling (at least with road bikes) and people may be unaware that light frames,components and wheels can be easily damaged unlike heavy city bikes. And never have experienced broken spokes, bend rims, scratched paint, broken seatpost, ... .
While lying on the floor a bike can be damaged by a passing car or anybody walking around, so why do that when there is a wall or something nearby ?
Because you don't care or you are overconfident of the overall strongness of the materials. And therefore you can do things wrong like over tightening bolts.

Same if you don't have thieves where you leave, you are not used of taking care of your belongings.

mattr wrote:
Antoine wrote:Could the rim strength have been affected by excessive heat (or cold) during storage ?
No. Not even if it was a composite rim.

are you sure about that, Aluminium frames can be damaged by the heat

RTW
in the industry
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by RTW

Antoine wrote:I was thinking South Korea is pretty new in cycling (at least with road bikes) and people may be unaware that light frames,components and wheels can be easily damaged unlike heavy city bikes. And never have experienced broken spokes, bend rims, scratched paint, broken seatpost, ... .
While lying on the floor a bike can be damaged by a passing car or anybody walking around, so why do that when there is a wall or something nearby ?
Because you don't care or you are overconfident of the overall strongness of the materials. And therefore you can do things wrong like over tightening bolts.


Keep digging. Are you basing this on anything, or just prejudice?

Have you ever been to Korea?

I know you probably don't mean to be insulting, and you are just questioning the general treatment of these bicycles which lead to this incident. But it is conjecture, based on photographs. It just comes across as racism.

by Weenie


joejack951
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by joejack951

Antoine wrote:are you sure about that, Aluminium frames can be damaged by the heat


The aging process of the -T6 heat treatment for 6061 is done at 325°F (160°C) or above. If you aren't exceeding those temperatures, you aren't compromising the metal. Welding produces very high temperatures and that can certainly affect the metal, but we're talking temperatures nearly an order of magnitude higher than the aging temperature.

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