How to fix? Left side crank arm popped
out. Shimano M8100 crankset. If I reattach the crankarm and tighten the 2 opposing bolts on the crankarm, it won't stay on. Should there be an additional bolt in place?
This happened mid-ride I'm not sure if I'm missing any pieces.
by Medium_Scholar9719
6 Comments
You’re missing the preload bolt, but the 2 bolts should be enough to hold it on.
tighten alternating to 12Nm
It’s not been fitted correctly, now the splines are fucked.
Doesn’t look like you have enough axle engagement
You haven’t got enough of the axle sticking out to attach the crank arm. User error
Are these OEM?
I ask because (and I could certainly be wrong here) the amount of exposed spindle looks too short on the non-drive side. Are there spacers on the drive side that shouldn’t be there? Do you know your bb shell width.
Realistically, even if not preloading the crank with the preload dohicky, the two bolts should still hold the crank arm in place provided there is enough spindle to attach to. This would also explain why the preload bolt is missing – it could not fully engage on the spindle threads because it couldn’t reach them.
To me, this looks like when I tried to put GRX cranks on a gravel bike not realizing it had mtb bb spacing. I’d start by measuring the spindle length, measuring the BB shell, and ensuring compatibility.
Edit: you can see how little of the crankarm is engaged by how boned the splines are in the video. Eeeek. Did you buy the bike like this? Second hand? Did you source and install this crankset yourself? Curious what the story is.
These older Shimano cranks love to do this.
The preload bolt (which is plastic) probably wasn’t tightened, has come off and gone AWOL, and this is the result.
If you haven’t fucked the splines a new preload bolt is easy and cheap to source.