I bought a Nashbar AL-1 road bike awhile back (didn't want to invest too much, wasn't sure I'd be too into road) and so far it's been great. However, I want to switch from a triple to a compact crankset. I currently have an isis bb and the compacts I'm looking at also take an isis, so is it simply a matter of off with the old and on with the new or is there a width difference that precludes using the same one? Thanks