1991 Kona Fire Mountain BB replacement

[Elthrin]

I have a pretty much original 1991 Kona Firemountain, only real issue I have (apart from needing a respray) is that I need a Bottom Bracket needs replacing. The old Tange unit has had it. It is a standard 68mm British Tapered Square with a spindle length of 125mm (measured)

I am thinking of replacing it with a Shimano BB-UN55 but that only comes in a 122.7 or 127 spindle. Which one do people think I should go for? I am assuming the 127????

 

[retroyetirigid]

If the cranks are a bit worn (but still useable) on the taper or you had minimal clearance then use a 127. If there was plenty of clearance between chainrings and chainstay then 122.5.

 

[al-onestare]

That's a tricky one. I think you should be fine with a 122 because it's a pretty slim frame and the rear stays don't branch out too much. 127 might be too long...but as above, it depends on how worn the cranks are.