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Warning: a stripped pedal thread on a rental bike in Moab taught me a hard lesson | Bicycle Mechanics - Vivisector

Warning: a stripped pedal thread on a rental bike in Moab taught me a hard lesson

I was working at a shop in Moab last season when a customer rolled in with a rental bike that had a crank arm pedal thread totally stripped out. The rider had tried to swap pedals themselves and cross-threaded it badly. The shop I was at had a policy of just replacing the whole crank arm, which meant a $75 part plus labor for a simple mistake. It felt wasteful and expensive for the customer. That day, I went home and ordered a helicoil kit for M14x1.25 threads, the standard pedal size. Now, for simple aluminum crank arms, I tap and insert a helicoil. It takes about 20 minutes and costs maybe $10 in parts, saving the crank from the scrap pile. Has anyone else found a good, reliable fix for this besides a full replacement, or do you think it's not worth the risk?

4 comments

4 Comments

the_emma6mo ago

Is a helicoil really strong enough for pedal forces? I'd be worried about it pulling out.

robert_ross956mo ago

But what do you think is actually going to pull it out? The force on a pedal is mostly shear, trying to snap the spindle. The helicoil threads are just holding it in place. A proper install should be stronger than the original hole.

adam_baker5mo ago

Funny enough it's kinda like how people worry about zip ties on a motorcycle until they see them holding brake lines on a race bike. Same deal here, the helicoil just becomes the new stronger baseline for the threads.

susan816mo ago

Helicoils are the shop secret for a reason. That steel insert is way stronger than the soft aluminum it replaces, so pulling out isn't the worry. The real risk is the customer trying another home mechanic special and stripping it again.