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Crankset Wobble

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Crankset Wobble

Old 12-12-10, 03:55 PM
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Crankset Wobble

Over the last year I have been getting into cycling, and I recently upgraded to a used 08 Scott CR1 Pro with a SRAM force groupo. The bike shifts fine but I recently noticed that the crankset wobbles from side to side slightly (see video). What would be the fix for this (hopefully not a new crank)?

Thanks!

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Old 12-12-10, 04:47 PM
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grab the drive side crank and push it in/out axially, do you feel play? if yes then the crank will need to be removed, splines greased and retorqued. if their is no play then the spider is bent because i saw both chainrings moving in sync.
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Old 12-12-10, 06:10 PM
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If there are no BB problems , then its just chain ring run-out, not perfectly flat.
I'd say ride the bike and see if it matters functionally, moving down the road,
rather than spinning the cranks and looking at them.

It may not, the run-out seems rather slight.

if it does, you may wish bend the chainring, but as you have a critical eye
to know it's right , you need machinist's dial indicators
to check your accuracy with precision feedback measurements..

Last edited by fietsbob; 12-12-10 at 06:13 PM.
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Old 12-12-10, 06:21 PM
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Someone please correct me if I'm wrong here, but I believe Force cranks are carbon fibre with the right crank integrated onto the spindle. As such there's very little that can be done to straighten them.

I suggest you have a dealer familiar with force cranks give it a look, rather risk making things worse with a brute force attempt at a fix.
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Old 12-12-10, 07:36 PM
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A close look at the video shows that it is not just the ring, but the crank itself (blue in video) that is wobbling. I would think that if FBinNY is right about it being carbon, the only fix may be replacement.
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Old 12-15-10, 08:02 PM
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Bummer. I will bring the bike to the local shop, but most likely I will need a new crank? I rode the bike a couple times and haven't had any issues with shifting, but I am worried that overtime this wobble will cause me to change the change and other components more often.

Thanks
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Old 12-16-10, 11:43 AM
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is there any play? perhaps it's an installation issue.
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Old 12-16-10, 12:01 PM
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you can tell the entire crank is wobbling by putting on a mini level onto the pedal while securely holding the bike upright.
if the level gives center at the 3' and 9' positions, but not 12' and 6' positions, then it's the entire crank.
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