so according to sheldon brown:
the sugino xd600 crankset needs a square bb 113-118mm
i have a 110mm bb on the thorn sherpa so i get a little rubbing when in the lowest gear combo. i'm not sure if this is simply an annoyance or if it can cause significant damage to other components??? (please comment!)
so looking at sjscycles.co.uk there are a selection of 68mm bb's that seems to be suitable, but what is the difference between them: un51/52/53; un72/3; un54?????
also what length is advisable? the shortest possible? i.e. 113mm. or is there any benefit to a longer spindle? 115-118mm??