Crank arm fell off?

PB Forum :: Mechanics' Lounge
Crank arm fell off?
  • Previous Page
  • Next Page
Author Message
flag hazdxb
Posted: Sep 12, 2011 at 9:15 Quote
My crank arm fell off today, and I have no idea why mainly because I have no idea how cranks/BB are fit onto a bike. It had been creaking a few days earlier so I had tightened it but there was no creaking around the time it fell off. So could you guys lemme know what part I am missing, or has been damaged (though it doesn't look like it) so that I know how to get to fixing it? Oh and I have Shimano Deore crankset
Thanks

photo

photo

photo

photo

photo
flag J-oryx
O+
Posted: Sep 12, 2011 at 9:30 Quote
Loosen the 2 socket head bolts on the crank arm. Clean the inside of the crank arm, the face surfaces, and the axle stub very well, and look for serious damage to the splines. If they're not completely boned you can regrease the axle, slip the arm back on (it's indexed with one large spline) fiddling with the plastic thingee fit into the split in the crank arm (a pin on it falls down into a hole in the axle, if it's the same as an XT..)

Then tighten the socket head bolts on the crank arm to the specified torque. Which I don't do. I just wind them down with a drive until they are "tight." I have never had an axle fail or have had the crank arm fall off. XT hollowtech 2 on both of my bikes.
flag hazdxb
Posted: Sep 12, 2011 at 9:52 Quote
J-oryx wrote:
Loosen the 2 socket head bolts on the crank arm. Clean the inside of the crank arm, the face surfaces, and the axle stub very well, and look for serious damage to the splines. If they're not completely boned you can regrease the axle, slip the arm back on (it's indexed with one large spline) fiddling with the plastic thingee fit into the split in the crank arm (a pin on it falls down into a hole in the axle, if it's the same as an XT..)

Then tighten the socket head bolts on the crank arm to the specified torque. Which I don't do. I just wind them down with a drive until they are "tight." I have never had an axle fail or have had the crank arm fall off. XT hollowtech 2 on both of my bikes.
Seems like a simple enough fix, the procedure you listed makes me think that the bolts weren't on tight enough and so the crank arm slipped out. Would that be correct? I checked the splines and they all seem to be fine so I guess i'll just do what you listed above.
flag J-oryx
O+
Posted: Sep 12, 2011 at 10:14 Quote
Yep, correct. Cranks are always falling off because people don't check the bolts. Square taper, isis, hollowtech, all the same.

Very simple. Clean everything, including the screws and the holes they go into on the crank. You're not working at a shop so you can be slow, methodical, precise. Hehe.

Put a little grease on the screw threads during reassembly as well.
flag hazdxb
Posted: Sep 12, 2011 at 10:29 Quote
Great! Thanks a bunch for clearing that up for me, i'll def be checking more often now.
  • Previous Page
  • Next Page

 


Copyright © 2000 - 2024. Pinkbike.com. All rights reserved.
dv42 0.012956
Mobile Version of Website