Square taper BB becoming notchy when cups are tightened up.

Posted on Tue 15th, December 2020

• #1

Juicy8

As above, new Campagnolo square taper BB which turns perfectly smoothly when uninstalled, turns in quite a notchy way when the cups are tightened up in the frame. The threads are fine and the previous BB worked perfectly. The only difference between the two BBs seems to be the new one has a lip on the driveside, where the old Miche Primato BB was flush with the BB shell.

What could this be? An uneven BB shell requiring facing??
• #2

fizzy.bleach

We're taking cartridge BB, right?i f you back the NDS cup off a shade, does that fix it?
• #3

Juicy8

Yeah cartridge BB - I installed it all as backed out as I thought sensible... NDS cup (which has the lip) flush with BB shell but not cranked down on it, NDS wound in enough to be vaguely equal in terms of what's sticking out. I took it for a spin earlier and nothing noticeable when you're riding but I'm sure it will shorten the life of everything. Maybe I'll try backing it out slightly now...?
• #4

Adhiero in reply to @Juicy8

NDS cup (which has the lip) flush with BB shell but not cranked down

You mean drive side right? Sounds like the nds is a tad tight. Try loosening in 1/16 turn increments or smaller.
• #5

Juicy8 in reply to @Adhiero

Thanks, that seems to have helped a lot although not solved the problem entirely - think it needs facing. Cheers :)

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