Bicycle Mechanics - Crank Replacement

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Ryleeryno
09-25-06, 05:37 AM
http://cgi.ebay.com/SHIMANO-ULTEGRA-10-SPEED-CRANK-BB-NO-RESERVE-NEW_W0QQitemZ220030584002QQihZ012QQcategoryZ56195QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

I need to replace my crank on my 9spd Trek 5000. Its a Bontrager with an unknown BB. In 500 miles I've already had to tighten the crank arms twice and it doesn't shift how I'd like it to. It also flexs a lot.

I want to put on an Ultegra Crankset w/ BB. I found this great deal on Ebay but it is for a 10spd. Will it be compatible?

Thanks in advance.
-Ryan

tomacropod
09-25-06, 06:53 AM
I'd say yes it will be compatible. If you want to upgrade that's fine, but tightening crank arms is completely normal. In fact most fasteners require an occasional tighten. If it doesn't shift how you'd like it to you should turn your attention to the shifting system, which you will have to reset half of anyway with a new crankset.

- Joel
HillRider
09-25-06, 07:16 AM
I'd say yes it will be compatible. If you want to upgrade that's fine, but tightening crank arms is completely normal. In fact most fasteners require an occasional tighten.
That's not correct. If the crank arms are installed correctly and torqued to the proper level initially, they should never loosen.

BTW, do not continue to periodically retorque the arms to the final torque specs after riding for some time. The arms will "relax" slightly after use but will remain adequately tight. This is a particular problem with square taper bottom brackets as you will effectively "chase" the crank arms up the taper and eventually they are likely to crack.

tomacropod
09-25-06, 08:49 AM
500 miles would be considered a fair break-in period by many. Such a thing as tightening crank bolts at this interval should not be surprising. I was not clear in the original post though, most fasteners require occasional attention although tapered cranks shouldn't require any real attention after an initial period if installed correctly.

- Joel