Had a bottom bracket just... fall out on a group ride yesterday

We were climbing this hill near the river, and I hear this loud clunk from my bike. Looked down and the whole non drive side crank arm was hanging loose, with the bottom bracket cartridge just sitting in the frame, totally unthreaded. It must have slowly worked itself out over the last 50 miles. I had to walk the bike three miles back to the shop. Has anyone else had a square taper BB just decide to peace out like that? What's the fix, besides more threadlock?

3 comments

3 Comments

linda_ellis1423d ago

Man, that's a classic. Square taper can be sneaky like that. Did you check if the frame threads are still good? A shop needs to face the bottom bracket shell and chase those threads, then maybe use some stronger paste. Just threadlock won't cut it if things aren't square.

uma68523d agoTop Commenter

I saw a guy at the co-op last month with a stripped aluminum frame because his square taper crank kept coming loose. The shell was faced fine, but the crank arm itself had worn out its taper from rocking. He needed new cranks, not just a better fix on the frame. That's a pricey lesson if you don't catch it early.

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alex_nguyen15d ago

Yeah, chasing threads is key, but once that arm's taper is wallowed out, you're just chasing your tail, right?