Had the worst day of my wrenching career last Tuesday

I was swapping a bottom bracket on a 2018 Trek Domane and the threads just stripped right out of the frame after about 3 turns. Turns out the previous mechanic had cross-threaded it and hid it with grease. Has anyone else had to deal with a warranty claim on a carbon frame for something like this?

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the_logan3mo ago

I was with you until you said "3 turns" on a bottom bracket. No way a BB30 or even a threaded BB gets 3 full turns before binding up if it was cross threaded. More like a quarter turn and then it's locked. You sure it was 3 turns? That sounds like the threads were already gone from the start and you just pushed it through without feeling it bite. Carbon frames are tough for warranty claims too, since Trek always asks for proof it wasn't user error during install.

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josephl673mo ago

Exactly. Three full turns before binding is basically impossible unless the threads were already chewed up. I've cross threaded a bottom bracket once on an old aluminum frame and it locked up before I even made a full rotation. That thing was done. If you got three turns in, either the aluminum insert was already stripped from the factory or someone ran a tap through it previously and damaged the threads. Trek is real stingy with carbon frame warranties too. They'll ask for pictures, receipts, and even want to inspect the bike themselves before they approve anything. Most shops won't even touch a warranty claim unless you bought the bike new from them and they did the build. You pretty much have to prove you didn't install it wrong or take it to some random shop.

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