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  1. #1
    . monkey's Avatar
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    Crank arm keeps coming loose

    The non-drive side crank arm on my roadie keeps coming loose. The threads on the bottom bracket are fine, the crank arm looks okay. I put a new bolt on it and I have the same problem. Any ideas?

  2. #2
    put our Heads Together cerewa's Avatar
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    Here's the way I was taught to install square-taper crankarms:

    -put it on and tighten the bolt as much as you can. (don't use any kind of wrench extender though.)

    -go ride for a minute; try standing on the pedals with the right pedal forward and then with the left pedal forward.

    -tighten the bolt like in step 1.

    after that, it should stay put.
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  3. #3
    . monkey's Avatar
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    I cranked it on as tight as I could, rode for a while, then tightened again. Still coming loose.

  4. #4
    Senior Member
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    After you tighten the crank take the bolt out and see if the end of the spindle is level with the suface of the crank that the bolt pushes on. The bolt may just be tightening onto the end of the spindle and not on the crank. If that is the case you either need a new crank or you must grind a couple of mm off the end of the spindle so the crank can be forced onto the taper.

  5. #5
    Senior Member sydney's Avatar
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    and if the crank arm interface is hosed,from being ridden loose, the real fix is a new arm.

  6. #6
    Senior Member sydney's Avatar
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    Quote Originally Posted by cerewa
    Here's the way I was taught to install square-taper crankarms:

    -put it on and tighten the bolt as much as you can. (don't use any kind of wrench extender though.)

    -go ride for a minute; try standing on the pedals with the right pedal forward and then with the left pedal forward.

    -tighten the bolt like in step 1.

    after that, it should stay put.
    There is a recommended crank bolt torque,and lacking a torque wrench, www.sheldonbrown.com/tork-grip one needs to be using a long enough wrench to start with.My 4" metric cresent wrench wouldn't cut it.

  7. #7
    Senior Member wrench_meister's Avatar
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    agree with sydney...

    since it keeps coming loose and you keep retightening it and it still comes loose, your best bet is to replace the crank arm. You may have warped the crank arm...
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