Earlier while trying to sort out my chain guide I noticed that the non driveside BB cup wasn’t in flush to the frame. I figured I would remove, regrease and re-install. Its was very very difficult to get out. I don’t think it was cross threaded but the threads were a bit worn looking. The frame BB threads looked ok, so I decided to install a new BB I had. However there was a lot of resistance when I tried to install it. I figured I would stop before i caused any damage.

Any ideas on whats happened? The BB threads are intact (as far as I can tell) so would a BB re-tap or chase help the situation? Is this a thing that most LBS’ can do or do I need to go and find a specialist re-tapped or whatever its called?

New BB.

They’re cheap as chips.

if the new BB is being funny going in then definitely get someone to chase the threads with the correct tool. Any decent bike shop with a workshop will have the tool to run through it.

Does sound like your BB shell could do with a bit of TLC. Would have thought most (all?) LBSs should be able to do this.

It doesn’t take much gak to clog up a thread that fine, I’d clean all threads meticulously with a rag over my nail and then then lightly grease and try again.

Try white spirit and toothbrush, make it clean and shiny

A tooth brush could definatley do the trick!I did give it a good dose of wd40 and then greased it up prior to installing the new BB but there was still a lot of resistance.

You need to Chase out the thread. Either buy the tool or take it to your lbs. If its been cross threaded the thread will have been compromised slightly. Chasing them out will correct this. You’re definatley right to question any resistance when screwing in a new BB cup as there shouldn’t be any.