I’m replacing the cranks on my 2006 Bianchi Pista with some longer Sugino XD cranks (square taper). What bottom bracket should I buy? The BB that came stock on the bike was a splined 108x68 Truvativ, should I replace with the same length Truvativ but in square taper or just go with the Sugino BB (103x68) that is ment to be paired to the crankset? I guess I’m asking if the Sugino BB will be compatible with my bike and will I notice the narrower BB size?
Many thanks,
David in VA
I believe that the Sugino BB will be compatible if a 68mm came off of your bike. The 68 refers to the bb shell length, which is usually 68mm or 73mm. The 108 refers to the spindle length in mm. I think that a 108 square taper would work fine, but you may as well go with the 103 that is designed for the cranks. I doubt that you will notice any appreciable difference in the narrower bottom bracket as the crank arms may be offset different than the splined ones to give the same Qfactor (the distance between the pedals).
Go with the BB that is meant to be paired with the crankset. A BB that is too wide will throw off the chainline.
You cannot really compare BB widths between different cranksets. for example, my 1980 Campy Record cranks take a 115mm (or thereabouts) square taper BB. My 2002 Chorus cranks take a 102mm square taper BB, but both have roughly the same Q factor and chainline.
Thanks guys for both posts. I went ahead and bought a Sugino BB on ebay, thanks again…Dave in VA