The day I figured out I was overtightening derailleur bolts for years

I was swapping out a rear derailleur on a customer's bike last Tuesday, the same job I've done a hundred times. After I got it all set, the shifts were rough and the hanger looked tweaked. The guy I work with, Mike, came over and just tapped the bolts with his pinky and said 'you're cranking these down like lug nuts.' I always thought tight was good, but now I realize I was probably warping the mounting plate on every install. Has anyone else had a moment where you found out you were using way too much torque on something simple?

3 comments

3 Comments

the_sean3d ago

Tight is tight and too tight is broke, I killed a derailleur plate on a Campagnolo Record once doing the exact same thing. The bolt ends bottomed out in the threads and cracked the whole mounting area when I went for that last firm turn. A beam torque wrench is honestly the best twelve bucks you can spend, total game changer.

the_alice3d ago

130 inch pounds is the spec on some Shimano derailleur hanger bolts, and I always just guessed until I bought a beam style torque wrench from Harbor Freight for 12 bucks. That tiny amount of force feels like barely anything compared to what I was doing before, just a firm snug with a short Allen key. I bet half the shifting problems people blame on cable stretch are actually from bolts being too tight and pinching the plate.

jenny_lee3d ago

Those small bolts strip easy too, not just the plate. Seen cracked derailleurs from overtightening?