Shoutout to the guy who told me to never use a torque wrench on a bottom bracket

I was working on a customer's carbon road bike in the shop last Tuesday, installing a new press fit bottom bracket. Another mechanic, let's call him Mike, walked by and said 'you know, you should just feel that in with a big wrench, torque specs are for amateurs.' I ignored him and used my Park Tool TW-5.2, set to the 40 Nm the manual said. Halfway through the second ride, the customer brought it back with a horrible creak. The bracket had worked loose because the carbon shell was slightly out of round, and the exact torque wasn't enough for a proper seat. I had to pull it, face the shell, and reinstall with a good dose of paste and a solid 'feel' on the press tool, no torque wrench. Mike was smug, but he had a point for this one specific job. Has anyone else run into a situation where the book spec just wasn't right for the real world part?

2 comments

2 Comments

bell.evan10d ago

My old shop foreman had a rule for press fit BBs in carbon frames. He'd say to hit the book spec with the torque wrench, then add another quarter turn on the press tool by hand. The paste does most of the work, but that extra bit of seat matters when the shell isn't perfect. I still use the torque wrench every time, it's the only way to know where you started. After that, you're just making sure it's not going to move.

thompson.tyler10d ago

The torque spec is still the right starting point. Your issue was the out of round shell, not the tool. Proper facing fixed the problem, not skipping the torque wrench.