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Crank breakage
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Boogerd_Fan



Joined: 07 Oct 2006
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Location: Bratislava, Slovakia

PostPosted: Sun Aug 18, 2013 12:13 pm    Post subject: Crank breakage  Reply with quote

Today i came a cropper at 35kmph... standing out of saddle and left crank arm suddenly detatched itself from bike... no broken bits on me.. a lot of road burn and a frustrating 20km riding on one leg to get home. Thinking i'm kind of fortunate that this happened today, on a solo ride, in the countryside without traffic vs. some other routes/rides coming up on main roads + group rides...

Now i'm cleaned up.. i'm starting to worry about the bike repair...

the crank arm is still in 1 piece. not sure if the bottom bracket is what snapped... but the snap occurred actually in the spine/thread of the bottom bracket:



crank arm = intact
spline joining btm bracket with crank arm - well...1/2 of it is in my crank arm.. and another half is still in my bottom bracket!!


I'm mechanically competent as a fish out of water... so this is going straight to the bike shop in the morning.. but would appreciate some insight, into how its gonna be fixed... what new parts (if any) are required... so i can evaluate the cost.. Smile

Just thinking how on earth this is going to be repaired?!
Assuming the least damage is new btm bracket (as spline is unsavable in 2 pieces)... but worried i'll need new cranks/drive train too...
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MAILLOT JAUNE



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PostPosted: Sun Aug 18, 2013 12:23 pm    Post subject: Reply with quote

Sorry I can't help you on this one, but just glad you didn't come off worse and are in one piece. Good luck with the repairs.
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gerry12ie



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PostPosted: Sun Aug 18, 2013 12:56 pm    Post subject: Reply with quote

Blimey Boogie turn down them watts! Wink

Something very similar happened a mate of mine a couple of weeks ago and it cost him a new BB.  The LBS were able to extract the broken splined adaptor from the crank arm and AFAIK its been ok since.  Is the BB shell okay?
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Boogerd_Fan



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PostPosted: Sun Aug 18, 2013 1:15 pm    Post subject: Reply with quote

BB Shell is indeed intact... hopefully the LBS here are as skilled as your mates.
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Bartali



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PostPosted: Sun Aug 18, 2013 6:00 pm    Post subject: Reply with quote

gerry12ie wrote:
Blimey Boogie turn down them watts! Wink

Something very similar happened a mate of mine a couple of weeks ago and it cost him a new BB.  The LBS were able to extract the broken splined adaptor from the crank arm and AFAIK its been ok since.  Is the BB shell okay?


Main thing is that you are okay ... that's good!!

I think the same as Gerry.  It could be worse, but most likely just a new BB.
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berck
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PostPosted: Sun Aug 18, 2013 6:07 pm    Post subject: Reply with quote

Welcome to the club BF. Wink I broke my spline about three years ago. More internally than at the crank arms. Are you riding with Shimano or Campag?

I was able to call the misses and have her pick me up when I broke mine. I couldn't even pedal anymore because the spline wasn't allowing it to.
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Last edited by berck on Thu Oct 10, 2013 2:38 pm; edited 2 times in total
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Boogerd_Fan



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PostPosted: Sun Aug 18, 2013 6:45 pm    Post subject: Reply with quote

Shimano .... i'm quite lucky it happened early in today's ride (8km from home).. so one-legged ride back home wasn't so far... had it happened yesterday where i was 50-60km away and pumping some serious efforts on hilly intervals... without my wallet or phone.. yeah, that would've been murphy's law... but this was just pick myself up, and get going again.

here's some nice pics (apologies about the size):






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Fontfroide



Joined: 07 Apr 2008
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PostPosted: Sun Aug 18, 2013 10:05 pm    Post subject: Reply with quote

Glad you are OK.  My guess is that it won't be a big job.  But what a surprise, of the bad sort.
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berck
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PostPosted: Mon Aug 19, 2013 1:56 am    Post subject: Reply with quote

Hmm, mine was Shimano Ultegra. Glad it worked out well.

I expect Bart to chime in here soon. Wink
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Boogerd_Fan



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PostPosted: Mon Aug 19, 2013 11:01 am    Post subject: Reply with quote

Yes, admitting to having Shimano parts is sure to not go un-noticed Very Happy

Well, LBS wrote off the cranks as well.. the snap is in the center axle... so new cranks required. Bit more expensive repair than i wanted, but OK - it will tidy up the damage i'd seen on the drive train side from a spill earlier in the year anyway Wink

on some diagnosis, there was some talk about the bolt being tightened too tight, which put too much pressure onto the thread... the critical failure is in the crank arm screw thread (big crack)...
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Bartali



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PostPosted: Mon Aug 19, 2013 1:25 pm    Post subject: Reply with quote

berck wrote:
Hmm, mine was Shimano Ultegra. Glad it worked out well.

I expect Bart to chime in here soon. Wink


I was so tempted ... but didn't really want to gloat at such a time.  Anyway, but for the grace of god ...

BF - I'm guessing the torque limit for a BB to be something between 50nm - 70nm, which is quite difficult to over do without some serious muscle or a bloomin long BB wrench.
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Boogerd_Fan



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PostPosted: Mon Aug 19, 2013 2:22 pm    Post subject: Reply with quote

I would like to think its the latter...

LBS guy was showing me the bolt that goes on after the pedal, showing me the 0.5 neutons or whatever that is the max torque to put on there.

That bolt has been coming loose at any ride over 100km in last 2-3 months. so i was making sure it was on good and tight on recent rides. It was explained to me that tightening it so, could have damaged to screw thread or created the crack that eventually caused the crank centre axle to split at the btm bracket.

I'd much prefer the other explanation about leg strength Very Happy Very Happy but it looks like this is my mechanical ignorance that was root cause.
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Bartali



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PostPosted: Mon Aug 19, 2013 10:57 pm    Post subject: Reply with quote

So he's saying over tightening the pedal has caused the crank to crack in the centre?  Seems odd to me ... and even if the crank failed, I'm not sure why the BB would shear?

Looks like a part failure to me through manufacturing error, crazy tightening of the crank bolt (which is hard to do with a regular 8mm hex wrench) or maybe as a result of your earlier spill?
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SlowRower



Joined: 22 Nov 2006
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PostPosted: Thu Oct 10, 2013 10:39 am    Post subject: Reply with quote

Boogie - I've only just seen this. Glad you survived OK! Hope the damage to wallet wasn't too bad. Something similar happened to me - broken spindle in FSA crankset - though luckily it didn't fall off. I got it replaced with a Shimano Ultegra unit, which I have to say is excellent.

On an unrelated note, I got Mrs SR an early birthday present - a new turbo trainer! We now have one each, so can do a little "side-by-side" when the mood strikes. Who says romance is dead? Smile
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Bartali



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PostPosted: Thu Oct 10, 2013 1:23 pm    Post subject: Reply with quote

There's got to be a joke in there about you both  having a ride in the garage and getting all hot and sweaty .... but I'm not saying it!!!
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SlowRower



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PostPosted: Thu Oct 10, 2013 1:45 pm    Post subject: Reply with quote

Bartali wrote:
There's got to be a joke in there about you both  having a ride in the garage and getting all hot and sweaty .... but I'm not saying it!!!


Very wise!
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berck
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PostPosted: Thu Oct 10, 2013 2:37 pm    Post subject: Reply with quote

Bartali wrote:
There's got to be a joke in there about you both  having a ride in the garage and getting all hot and sweaty .... but I'm not saying it!!!


Laughing Laughing Laughing Laughing
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SlowRower



Joined: 22 Nov 2006
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PostPosted: Thu Oct 10, 2013 7:00 pm    Post subject: Reply with quote

SlowRower wrote:
Bartali wrote:
There's got to be a joke in there about you both  having a ride in the garage and getting all hot and sweaty .... but I'm not saying it!!!


Very wise!


Our turbo sessions did overlap slightly today - Mrs SR's first 15 minutes coincided with the end of my session.

Despite the apparent rich potential for schoolboy humour, it would be fair to say that this was no laughing matter for either of us. I was suffering as badly as one would expect in the closing stages of a third turbo session in 5 days, whilst Mrs SR had to watch me turning more purple than Mr Ribena whilst apparently melting.  Very Happy
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MrsSR



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PostPosted: Wed Oct 16, 2013 12:34 pm    Post subject: Reply with quote

SlowRower wrote:
On an unrelated note, I got Mrs SR an early birthday present - a new turbo trainer! We now have one each, so can do a little "side-by-side" when the mood strikes. Who says romance is dead? Smile

Only just catching up on the forum after a few days away - I don't remember it being an early birthday present.  Evil or Very Mad
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gerry12ie



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PostPosted: Wed Oct 16, 2013 12:45 pm    Post subject: Reply with quote

Weren't you supposed to be getting something beginning with S-Works? Wink


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