Originally Posted by cavit8
the nice thing I've found about using cups and bearing bottom brackets as opposed to cassette is that you have more flexibility flipping the spindle or trying different spindle lengths to help with your chainline.
Most b.b. spindles are not symmetrical (thus one side being longer than the other) If you flip the spindle you may end up putting the cranks out of line with the rest of the bike. Anatomically this can throw your hips and/or knees out of alignment with the centerline of the bike. This can cause problems with joints and ligaments.