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  1. #1
    cmh
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    Should I replace my ISIS BB?

    After a couple thousand miles on my Felt F-55 w/FSA ISIS BB, there was a lot of creaking from the BB whenever I cranked hard - like going up hills. The shop that I bought the bike from said the threads just needed greasing. So, they pulled the BB, greased the threads and the creaking was mostly gone, but not entirely. The creaking ramped up to its previous volume after another 500 - 1000 miles and I just kept riding it that way. Now that I'm not riding that bike (because it is winter time), I am thinking of replacing the BB. However, when I remove the chain, the cranks spin freely and I don't feel any grittiness through the Al frame (holding the seat or down tubes). Does that mean the BB is still fine and I should just re-grease the threads? The BB now has about 4800 miles on it, mostly in dry conditions. I have heard the ISIS BBs can wear out rather quickly.

    Thanks in advance for any advice.

  2. #2
    Senior Member MudPie's Avatar
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    There a couple of items to de-couple:

    1. ISIS is a spline standard that defines the crank arm to spindle interface, just like Octalink is Shimano's splined standard.

    2. The BB bearings, and threads at the BB/shell interface are not ISIS. For example, an ISIS compliant BB does not dictate a certain bearing.

    In you case, I think #2 is the issue, since greasing the BB/shell interface made a difference. You might want to try to regrease the threads. I'm not sure of the material of your frame, but often (especially w/ titanium frames), some use teflon plumbers tape on those mating threads to quiet the interface.

    The bearings are probably in good condition, based on your description. Are the bearings quiet when you hand spin them or do they have a "dry" sound. If they do have a "dry" sound, then you might need a new bearings (which translate to new BB).

  3. #3
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    If the bearings are smooth and there is no play in the spindle when you push and pull on the crank arms, the bottom bracket is fine. A total of 4800 miles is barely enough to get a decent bb broken in and it should be no where near failure.

    Creaking of bottom brackets is epidemic in some frames. Grease may quiet it down for a while but a couple of wraps of plumber's teflon tape around the threads of both cups is more likely to quiet it down for a long time.

  4. #4
    cmh
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    Thanks for the advice - you saved me the cost of a BB, at least for now. I'll try to regrease the threads and see if that takes care of it. If not, I'll try the teflon tape.

    cmh

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