I have a similar question regarding BB/crank size and compatibility with my bike.

Five years ago I replaced the BB/crank on my 2004 Giant Rainier. It currently runs a Nashbar ISIS drive 48/38/28 (which needs replacing) with a 68x113mm BB (which needs replacing as well). I have shopped a Shimano Acera crankset with the same specs and a Shimano BB (square taper).

The confusion is if I get the 68x113mm BB, the crankset specifies a 122.5mm spindle length. Do I need to find a crankset with a 113mm spindle length? I ask because I am assuming the current 113mm BB fits the BB cup exactly, and that a 122.5mm spindle length would be too long.

Thanks in advance.