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    10 Comments

    1. TheDaysComeAndGone on

      I don’t understand how this could happen if you had both bolts tightened to 10Nm as per spec (and go back and forth tightening both bolts). If the splines look fine you could just risk using it (maybe with some retaining compound or carbon assembly paste to get all the friction you can get on the surfaces).

      Edit: Oh and of course make sure you set the bearing preload correctly before you tighten the pinch bolts and make sure you have the correct amount of spindle spacers (though I guess if you had too many spacers you would be unable to engage the small safety tab between the pinch bolts, so this can’t be the root cause).

    2. GunnyWombat on

      Hard to tell how much damage has been done without seeing the crank arm indents which will be the ones to go as the softer metal. If you refit, make sure the bolts are torqued from 12-14Nm. You may be lucky and get away with it, if not you’ll soon find out again. You may also have to get a new plastic spacer with pin in it that sits between the bolts, if that has been damaged.

    3. Long_Ad2824 on

      This is not a problem if you install Biopace chainrings 90 degrees out of phase, and lower your saddle 7 inches.

      Loosen both pinch bolts on the non-drive crank arm, then screw the arm on as snug as you can with your fingers with the plastic top cap. If you didn’t get the arm on far enough that the indicator plate sits flush in the crank arm, the crank arm needs to be further down the shaft/splines.

    4. c0nsumer on

      You didn’t install the NDS crank arm correctly. RTFM from Shimano, *specifically* the part about alternating torquing the bolts one at a time, and the order of operations for end cap, retaining tab, and bolts.

      I’d wager significant money that you tightened one bolt, tightened the other, then called it a day. Doing this leaves the first-tightened bolt loose, and then this happens. If you didn’t do it up to the proper torque, then the problem is even more likely.

      Hopefully you didn’t damage the splines on the spindle or crank arm, because if so, it’ll never be right again and you’ll need to replace it.

    5. Bufordtannan on

      I’d just buy a new arm..you’ll forever be waiting for this to happen again and not be able to ride to 100% enjoyment.

    6. eliaskeeuh94 on

      Got the bike serviced after my crash..
      The bike shop might have some explaining to do.. 🙂 thanx all for the input

    7. andyonabike on

      is that retaining tab on crank in place? make sure its sitting behind the pin before you torque the bolts.

    8. RaplhKramden on

      Wait, did you or someone else install the crank arms like that, only 90 degrees apart, or did something cause this to happen, like catastrophic bolt or arm failure? Whenever I’m reinstalling my drive-side crank arm (to clean or replace the chainrings) I have to remind myself to make sure that it’s 180 out of phase with the other side. Rookie mistake that anyone can make if distracted, but immediately noticed when you try to ride the bike, if not sooner.

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