Ok I'm going to ask a stupid, we'll sort of question. First I understand English v Italian threading. But I'm a wee bit confused at spindle length v. BB shell width and correct bb width. Or let me put it another way: I'm building up a vintage Italian frame with a Campy BB installed. (square taper). Now will a shimano square taper crankset just bolt on or do i need a Shimano square taper bb. Also,my understanding is English threaded bb shells are 68 and Italian's are 70 so italian threaded bb's are always wider in general? I know if I use a double v triple there will be a variation in width but In the end how do I size a bb to ensure proper chain alignment? Is it shell width and desired crankset? How about rear spacing? If I go with a 130 rear wheel say a 9 speed do I need a wider bb? Someone make it easy for me please!

Spindle Length
"Since your chainline is constant, your bottom bracket spindle length depends only on your cranks, not your frame (with the exceptions noted above). Depending on the crank design, the spindle length can vary."


So is the taper on a dura ace 7400 the same as a campy crank similar vintage? ISO v J.I.S

The Dura-Ace 7400 crankset was advertised as cross compatible with Campagnolo bottom brackets, and vice versa.

^ By who?

whats the length of your bb?

The DA 7400 used a 113mm spindle on Italian BBs. The mid 80's Campy is not really ISO (that started in '94), but sits about "halfway" between ISO and JIS. The Campy Italian spindle (if Record) would be 115.5mm, so my guess is that the 7400 crank will have a good chainline if you put it on the Campy spindle. But just try it - it can't hurt anything.

(caveat - The Record spindle is asymmetric, I don't recall if the DA is)

Running a spindle a mm or two shorter can be good, provided you have enough clearance between chainrings and stay. It lets you run the big-big combination if necessary. Not that you'd do it all the time.

Just sayin'.