I have a Schwinn Passage touring bike setup as my commuter which is in need of some serious BB work. Most likely a complete replacement. The current bottom bracket sindle is an old 3S with a right side length of 37.5, left side of 32mm. ie: asymetrical lenghs, which were common on older cranks (this one is a Sakae CX).

Sheldon Brown's website suggests a Shimano UN-52/72 replacement with a spindle length of 127mm. This, however will cause the non-drive side crank arm to be further out, something that my left knee is sometimes tempermental about. Thus I'd like to reduce the change on the left side as much as possible.

I could try to install a UN-52/72 of length 122mm in an effort to keep the left side arm as close inboard as possible. By my novice calculations I figure that would move the crankrings approx 1.5mm inward as well. Anyone see any potental problems (other than the chain rings striking the frame, which is doubtful from what I saw when looking at the crank last night.

Any suggestions, advise would be helpful.