Shimano BB plastic cup cross threading

hi,

i'm currently installing a shimano un54 BB and the fixed cup side screwed in fine.

unfortunately i am unable to get the plastic cup that screws in the other side to tighten properly without cross threading it.

has anyone come accross this sort of problem before?

any solutions?

thanks

skinnygav

where is your frame from? - both sides threaded the same way? - sounds like a french bb...

google is your friend

Yeah, I've had this problem. Are you absolutely sure that the bottom bracket threading is compatible with the frame? If so, I'd be prepared to bet that chasing the threads of the bottom bracket shell will solve the problem, even if they don't look that dirty just now. Those horrible plastic retainer rings aren't very forgiving. The shell threads need to be just so.

Btw, make sure you don't stuff up the threading on the plastic ring cos it's bloody hard to get a new one as a spare part without ordering online.

it is a british frame, threaded opposite ways.

chasing the shell? i've already cleaned and de greased the threads..

so my initial idea of getting it as tight as possible then hitting it with a hammer isn't a good one?

Just say no to hammers (unless you're installing a headset. :-P )

Look inside the bottom bracket shell with a torch. Check for obvious damage to the threads. If you can't see anything suspcious, chasing is the way to go, imo. It'll cost you a tenner at most.

Just say no to hammers (unless you're installing a headset. :-P )

Look inside the bottom bracket shell with a torch. Check for obvious damage to the threads. If you can't see anything suspcious, chasing is the way to go, imo. It'll cost you a tenner at most.

sorry for being a noob Soweto888 but what is chasing?

Chasing is using a tap to clean existing threads. For some applications (and certain bits of a bike) you can buy special taps that are designed just to chase - they remove unwanted debris and optimise the threads without cutting away lots of metal. I'm not sure that a specific chasing-only tool exists for bottom bracket shells. That's neither here nor there, though. Your LBS will be able to clean them out with a tap.