Originally Posted by
Kimmo
No, the pulley can't be too big, but as long as the hole is big enough that'll do. If it's much thinner or thicker you'd need to shim that pulley or the other pulley with a pair of washers.
It won't matter if the pulley's sitting a mm off-centre of it's bolt in the cage, and you can calmp it centred if you like anyway.
Yeah, but a cartridge bearing craps all over a bush. The best pulleys are the fancy BB plastic OEM ones... haven't seen plastic aftermarket ones aside from cheapies.
I would kinda think that any pully that's too big couldn't actually be installed. 'Doesn't have to be spot on' to most people would nean 'should be close but doesn't have to be an exact match'. Hope that clarifies things and sorry if initially that went over your head.
But the concept of sticking anything through a jockey wheel with no regards to minimum shaft diameter makes me think I'd rather not have you working on my bikes. Ceramic bearings, bearing wear and lateral play don't seem to be anything you'd be concerned about, and I am with the Ultegra, XT and XTR derailleurs I use. Using the recommended replacement parts means you don't have to shim or second guess ANYTHING. And thats what any professional mechanic would do.