180mm XT Crank issue- Mtbr.com
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  1. #1
    mtbr member
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    180mm XT Crank issue

    I run 180mm XT cranks on my 29er singlespeed and I have pulled the non drive side crank arm off for the third time. The bolts are tight and the little safety pin dohicky is installed. I even run a Saint endcap made of metal and it still won't hold. I am 6'3" 230 lbs man with a size 13 shoe. Do I need to stay away from external bottom bracket cranks? Is it just a fluke? Am I just too much man for Japanese componenty? Suggestion please.

  2. #2
    openwound
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    So the little metal end cap -- the saint part -- it's pulling out, too? Have you tried cleaning it and the spindle threads and putting a little blue loctite on it?

    When you tension the two pinch bolts are you tightening them at the same time? If you're doing them one at a time, one will always be a little looser than the other.

    I run xt's on a couple of bike and, though I'm 40lbs lighter, I've never had this kind of issue. I'm thinking it's a fluke but will wait to pass that judgement until the wiser ones chime in...whoever they are today.
    -- let's ride

  3. #3
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    The little cap is just to preload the bearings.
    If the arm is coming off, the pinch bolts must be loosening up. I'd tighten them up with a torque wrench. Then every ride, or even every time you stop, I'd check them for tightness.
    It you have to retighten them more than a couple of times then you need to try locktite on the pinch bolts. Try checking them every ride again.
    If that doesn't work, then you might be right, you're exceeding the design parameters

  4. #4
    openwound
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    Agreed/understood that the cap is only for bearing pre-load. But still, if it's backing its way out, then a little loctite on that might help, too.
    -- let's ride

  5. #5
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    Yeah, don't crank down that end cap with the big threads. If you do you'll be putting way too much thrust on your bearings and they're wear out quicker. From memory they only need around one newton-metre, while the pinch bolts use more like 14. But for those, you might as well crank them as tight as you need.

  6. #6
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    The end cap doesn't loosenup it just blows the treads off. It seems that the two bolts must be loosening. I will loctite them from know on. I'm thinking that when your hammering up a short climb with a turn in it I don't have a straight pedal stroke. It happens on left hand swithbacks when I'm out of the saddle. You get some bike lean and thats when it happens. Thanks for the ideas. I will figure it out.

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