sk8matt41

I recently bought an old bike to use to get around town and for weekend projects. As far as the make of the bike, all I know for sure is that it's a road bike from the 70's with 27'' wheels and says "Spartan" on it. Anyway, I want to get away from the cottered cranks and switch to a cartridge BB. I did the measurements, the metal housing that dictates the size of the BB is 70mm, and tightens clockwise, so am I wrong in assuming I will need an Italian one?

I also took a measurement of the length of the current spindle (again, it's cottered) and came up with 146mm, which seems significantly longer than any cartridge BB i have seen. I assume that the width of the crank arms themselves will push them out far enough to clear, but I am worried about the clearance between the pedals and the frame if I get a BB too small. I've been looking at the Shimano UN55, and the longest one I see in 70mm is a 115mm spindle. Shimano UN55 Square Taper Bottom Bracket | Chain Reaction Cycles. Am I overshooting with the 70x115mm?

Hopefully this wasn't already addressed, sorry if it was. I couldn't seem to find it.

Thanks in advance.
Matt

CACycling

Spindle length is determined by crankset so choose the crankset first and get a BB with the length required by that crankset.

sk8matt41

OK, thank you. And as far as needing an Italian BB goes... am I correct in thinking it's Italian?

Airburst

A 70mm wide BB shell where both sides are right-hand threaded (clockwise to tighten, as you've said) almost certainly has italian threads.

If the shell is actually 68mm with both sides right-hand threaded then it's french threaded.