I spend some time searching and did not get the specific answer sought after, but I cannot believe this topic hasn't been covered before. Perhaps I'm not using the right search option(s).
I have a 1980s Centurian with a traditional loose ball bb with lots of crud and an annoying grit sound when rotated. (The bike is a fixie conversion - all weather beater, fun to ride.... bike) I have a shimano Un72 sitting in the parts bin. The shimano cartridge did not thread in easily and stopped about 6mm or so into the travel. I never force things through for fear of stripping the threads so I stopped.
My question is whether there is a TPI issue? (Visual inspection showed that they look similar.)
I'll take a stiff brush to really clean the bb shell threads this evening, but is the desire to switch this out ill advised for compatibility reasons? Anyone encounter similar difficulty?
Thanks in advance for any assistance,