Oh...

So you are converting a bike that had a 1 piece crank so it can use a cartridge BB.

What you are going to have to figure out is the chain line you are going to need so you can get the correct length spindle on the BB. So if you haven't taken the crank out yet, then measure from the centerline of the seat tube to the center of your chain rings. If one ring, then to it's center plane. If more than one ring, then to the center plane of the stack. 2 rings would be between the two. And 3 rings would be to the middle ring.

Then you have to figure out what spindle length will give you that chain line with the model of crank you intend to use. Good luck. That's one of the reasons I quickly got rid of a nice riding bike I had for many years and got a bike that was made for the kind of cranks I wished to use.


By the way, what is bc? Electra bc, Phat cycle bc.