Crank arm coming loose

crispyj
crispyj Posts: 18
edited August 2012 in MTB workshop & tech
The left crank arm on my kona firemountain 2011 keeps loosening. I tighten the bolt up on it as hard as i can, and then after about 30 or so mins, it comes loose again. Can anyone tell me what is causing it, or how to fix it. It is an fsa crank.

Help will be much apreciated :roll:

Many thanks

Comments

  • nicklouse
    nicklouse Posts: 50,675
    which FSA cranks?

    they do make quite a lot of different ones.

    i take it it is the square taper fitting ones?

    the taper on the crank could well be now damaged or you are not tightening it to the correct amount.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
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  • crispyj
    crispyj Posts: 18
    They are square tapered, but kona dont say what model they are, they just say fsa, and I cannot see them on the fsa website :(
  • Chunkers1980
    Chunkers1980 Posts: 8,035
    Threadloc, do it tighter, or coke can.
  • cooldad
    cooldad Posts: 32,599
    Good chance if it's been ridden loose it will be stuffed. Bit of play and it just loosens off again.
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  • Myster101
    Myster101 Posts: 856
    Take it off and see if there's any ware on the the bb or the internals of the crank arm. If so it might be time to replace/upgrade. Or try sticking some thread lock on.
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  • The Rookie
    The Rookie Posts: 27,812
    I've yet to see an alloy crank arm where a hardened steel square taper BB axle......betting is the square in the arm isn't square anymore as Cooldad says, so you'll need a replacement.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • crispyj
    crispyj Posts: 18
    Thanks for your responses

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