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Left crank arm not transferring any power

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Left crank arm not transferring any power

Old 06-11-07, 06:17 AM
  #1  
kobayashi
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Left crank arm not transferring any power

I'm a new road rider and had the bike out on a grassy area doing the obligatory clip in and fall over SPD session. I picked it up for the most part in about 10 minutes and was riding but had to suffer one more fall. Went down on the left side and the left crank is no longer transferring power through the bottom bracket - it is still well fastened and spins smoothly, just doesn't transfer power.

edit...just adding that it's a Shimano 105 crank with a Octalink bottom bracket.

I'll take it into the shop tonight...but could anyone give me an idea of what damage I might have done?

thx

Last edited by kobayashi; 06-11-07 at 06:23 AM.
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Old 06-11-07, 06:32 AM
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Unless you've snapped the axle (seems most unlikely from a fall), I have no idea.

Not sure what you mean, either. Does the left arm turn independently from the right arm?
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Old 06-11-07, 06:41 AM
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Yes, the left arm spins freely with out any effect. I simply fell on some grass.
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Old 06-11-07, 07:07 AM
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sounds like a broken spindle but how could that happen from a slow-speed fall onto a grassy area?
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Old 06-11-07, 07:11 AM
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Maybe the crank arm acted as a lever with all his weight on the end.. and it somehow got transfered into the spindle.

Spindle breakage sounds very likely, if it's spinning without any resistance, than it's unlikely something stripped.

You'll need a new bottom bracket.
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Old 06-11-07, 08:12 AM
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Damn, that's what I figured...I only rode it for a collective 2 minutes or so and now, more waiting.

I'll take it to the shop and let you guys know the outcome. Thx.
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Old 06-11-07, 08:49 AM
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Originally Posted by JanMM
sounds like a broken spindle but how could that happen from a slow-speed fall onto a grassy area?
There is more load on the bike in a slow speed fall than in a normal travelling fall as the rider is falling with the bike rather than away from it.

I did the same years ago with a stronglight BB trying to ride under some bunting.
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Old 06-11-07, 12:11 PM
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Luckily, or unluckily, that wasn't the problem - of course, you all were making educated guesses based on the idea that the bike was actually built properly.

I'm no mechanic, so this was all explained to me but there were two significant problems compounding one another: Everything else is set up for a double, but the bottom bracket that the shop used was a triple; the teeth on the Octalink connection were not properly lined up with Octalink teeth on bottom bracket - the parts were merely mashed together and tightened. I was lucky the crank gave out when it did as I very nearly stripped my brand new crank

I thought about doing the build myself but didn't because I didn't want to make these kind of mistakes. A definite shop I will never be going back to is Cyco's on Hawthorne Avenue by the Rideau Canal in Ottawa, Ontario.

Bushtukah, on the other hand, on Richmond Road in Ottawa, Ontario has a pretty great repair shop with some really cool guys.

Thanks for your help everyone. I'm going to go enjoy my bike.
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Old 06-11-07, 12:20 PM
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Good resolution! Enjoy the ride.
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Old 06-11-07, 01:51 PM
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maybe you broke your leg when you fell over. Did you break your leg?
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Old 06-11-07, 01:59 PM
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Originally Posted by kobayashi
Everything else is set up for a double, but the bottom bracket that the shop used was a triple;
That's not good, but shouldn't have anything to do with your problem.

the teeth on the Octalink connection were not properly lined up with Octalink teeth on bottom bracket - the parts were merely mashed together and tightened. I was lucky the crank gave out when it did as I very nearly stripped my brand new crank
If the arm was torqued down properly this should have ruined the crank arm. The receiving splines are pretty soft. Bet it wasn't torqued right.

I'd say the shop that built your bike owes you 1) the correct bottom bracket, 2) a new crank arm, 3) an apology.
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