I'm trying to change the spindle in my '72 Schwinn World Voyageur to accept a triple crankset. I got the appropriate spindle (or so I thought) and when I installed it in the BB the Adjustable cup goes in too far to get the lockring on.

I checked the BB shell size with calipers just now and it is certainly 68mm just like the spindle I'm using. Is this one of those Thin Cups/Thick spindle things?

I know I need a 68mm spindle ....apparently just a slightly different 68mm spindle.

Am I better off just buying a cartridge unit?