Crank arm fell off. [thm clavicula]

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

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Was out for a nice ride through the hills when all of a sudden the crank arm decided to fall off. Couldn't find the bolt, cycled for a while one footed gave up and called the wife to rescue me.

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Butcher
Shop Owner
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by Butcher

An extreme weight weenie you are. Some bolts you cannot eliminate.

KCookie
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by KCookie

Lol, yes definitely need that bolt. So glad it didnt come off peddling 70km down hill. Could have been a different outcome.!!

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2old4this
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by 2old4this

Nearly the same thing happened to me. I looked down and saw the non-drive side Clavicula (with time 15...) nearly out (the cap and the bolt were gone.) Since then, any time I put them on, I use loctite twice on the bolt (put once, wait until it dries, put second time and then screw it in.)

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BRM
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by BRM

Modern bikes need more maintenance than old fashioned bikes from the steel era.
But a modern bike build with extra light /exotic parts needs even more checkups.

Loctite is a good idea but then use the proper way of applying
http://na.henkel-adhesives.com/industri ... -14064.htm

ChiZ01
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Joined: Wed Jan 01, 2014 6:20 pm

by ChiZ01

looks like a design problem, the only thing holding it was friction, that area need actual thread

Nefarious86
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by Nefarious86

What is wrong with friction? If it's assembled correctly it isnt an issue.
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itsacarr
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by itsacarr

Isn't that the same non drive side design that's being used on the new iteration of SRM's THM\Dura Ace "SRM" branded crank? Being used on two protour teams at that ... just curious if this was a design issue or installation ... or freak accident. I know many people who had installation issues with 7800 dura ace non drive side cranks who magically came off during riding.

Either way I always thought that was a brilliant crankset. Glad there was no injury involved.

KCookie
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by KCookie

Thanks, Me to, just lucky i was going up a hill rather than going down. Was very surprised when suddenly my crank arm was attached to my shoe flapping around. !!
Got a day off tomorrow so down to the LBS to get fixed with loctite as pointed out. !!

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RyanH
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by RyanH

No offense to kcookie but his shops have already had a history of sub par performance. I'm fairly certain if they actually read the lengthy booklet and installed it per instructions it would have never done that. Kcookie you really need to start wrenching on your own stuff, I'm amazed at how terrible your local shops are... And you keep returning to them!
Strava
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spdntrxi
Posts: 1545
Joined: Sat Jul 20, 2013 6:11 pm

by spdntrxi

happened to me last year .. same crank. Going uphill @ 600w.. nearly bit it.

I broke the carbon arm though..bolt still there.
Last edited by spdntrxi on Sun Nov 27, 2016 2:34 pm, edited 1 time in total.

beeatnik
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by beeatnik

RyanH wrote:No offense to kcookie but his shops have already had a history of sub par performance. I'm fairly certain if they actually read the lengthy booklet and installed it per instructions it would have never done that. Kcookie you really need to start wrenching on your own stuff, I'm amazed at how terrible your local shops are... And you keep returning to them!


Couple of cats who do World Famous Montrose have had the same issue. Anecdotal, I know, but it makes me doubt user error.

2old4this
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by 2old4this

Nefarious86 wrote:What is wrong with friction? If it's assembled correctly it isnt an issue.


I am kind of obsessive about following the instructions and applying the exact torque. Given the facts that
- THM changed the design between Clavicula, Storck, and SE
- Three people had the same exact issue

I am kind of inclined to toy with the idea that there may be a design issue.

Nefarious86
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by Nefarious86

A design issue when Both the pinch bolt and retaining bolt have not just come loose but had time to fall out? Surely there was movement or noise before the arm disengaged. Retaining compound is a pretty basic inclusion on parts like this, specified or not.
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KCookie
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by KCookie

I did hear metal hit the Tarmac, thought what the hell was that then my left foot was on the ground crank arm attached. Looked but just couldn't find the bolt.

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