BSA: this is the ENGLISH threaded standard bottom bracket. 68mm or 73mm wide, with variants of 83mm and 100mm. Less common now is the ITALIAN threaded standard that is 70mm wide and has right threaded cups on BOTH sides.
|BSA threaded, external bearing type|
|BB30's direct fit bearing is very simple|
BBright is also offered in a PF30 variant using the the same asymmetrical 79mm shell but with the PF30 ID of 46mm.
BB86: is a press fit ROAD standard developed by Shimano. The BB shell is 86.5mm wide with an ID of 41mm. This standard is compatible with 24mm or 19mm axle chainsets.
|BB86/ 92 cartridge unit|
BB90: is a direct bearing press fit system used by Trek bicycles, easily identified by the 90.5mm BB Shell width. This standard is compatible with 24mm axle chainsets.
All press fit designs can suffer premature bottom bracket ware if the shell is not correctly reamed. If the shell is slightly out of round it can deform the BB creating fast bearing ware. If a fame has an ovalized BB shell and it is not correctly reamed bearing failure will be frequent.
|BB standards made simple...|