Ok, I'm no obviously no bike mechanic- but I always think I can fix this problem but it just keeps occurring. The left crank and pedal always detach from the rest of the bike. It's happened a few times now. I'm not sure as to what the problem is, whenever It falls off I untighten the bolts, slap the crank back on and tighten it, it stays on for a while but inevitably falls off again. This is probably a stupid post and I just don't know shit about bikes, but i hope whoever sees this understands i am no cyclist.
by Key-Offer9000
5 Comments
Looks like shimano cranks, there should be 2 pinch bolts to tighten the crank down with. Id just swing the by the bike shop and see what they have to say. It’ll be quick and they shouldn’t charge for it. They’ll be able to troubleshoot what’s happening.
[deleted]
Thought this might help
https://youtu.be/iTJ3taJHOn8?si=KSla34gmM0ntSTgf
1.First you should wipe the spline and whole area clean,bolts too.
2.Add thin layer of grease.
3.Put the crank back on.
4.Tighten the preload ring fighter tight until there’s no side ot side play, but hsould still spin freely.
5. Apply Loctite 243 on the bolts threads or the crank, this is to keep the bolts secure for longer, it’s a medium strength thread locker, others exist, I mention this one cus I know it well, it’s easy to undo, but keeps it secure, apply a bit of grease behind the bolt head and the shim, this is to prevent corrosion and it getting stuck. (same principle on all bolts on the bike.)
5. Tighten the both bolts lightly a little, this means switching between them until each stop, then tighten mor eon each bolt with a bit more torque, keep alternating, and tighten until they won’t turn anymore, best to use a torque wrench as the torque required isn’t as light as stem bolts for example.
The pinch bolts have a torque spec of 12-14Nm there should also be a preload plastic cap for the non-drive side to take the lateral play out. There should also be a metal safety tab in the crank arm. But really, if it keeps falling off, there’s a chance the crank arm has been damaged and you should either take it into a shop and have them look at it, or buy a new left crank arm and preload cap.