Stripped a crank arm bolt on my old Trek this afternoon

I was swapping out a 105 crank from 2015 onto my commuter bike and the non-drive side bolt just gave up after 30 ft-lbs. The threads on the arm are completely gone now, and I can't find a replacement arm in the same silver finish. Anyone know if helicoiling aluminum cranks is even worth trying, or should I just hunt for a used set?

2 comments

2 Comments

the_derek13d ago

Funny you say that @elizabeth_gonzalez, but that crank arm is likely toast with a helicoil.

elizabeth_gonzalez13d ago

wait wait wait, 30 ft-lbs? that's barely hand tight for a crank bolt, most of them call for like 35-40. i stripped a crank arm once too but it was because i was using a cheap allen key that rounded out the bolt head, not the threads. that's wild that the threads gave up at such low torque, maybe that bolt was already cross threaded or something from a previous owner. heck, i'd be mad if i was you, that's a huge bummer for a simple commuter swap. helicoiling aluminum cranks is kinda hit or miss, i've seen it work on pedal threads but for a crank arm bolt it's gonna take a lot of force and the helicoil might just pull out. honestly i'd hunt for a used set, even if the silver finish is hard to find, you can always swap both arms and keep the old one as a spare part.