Originally Posted by
Dean V
68mm. This is the standard width for an English BB. 73mm would be weird. Italian (M36 x 24 tpi x right hand thread both sides) is 70mm.
The 73mm BB is a mountain bike standard BB width that was adopted by Santana. FSA tandem cranks are made to this standard and use a spacer when installed on a 68mm BB shell. Using an Italian BB on a tandem would put the thread locker and torque to the test with twice the power tending to unscrew one side of the BB.