Originally Posted by 46x17
Are you talking about the sugino or the shimano BB? The sugino should be symmetrical not longer on one side. Shimano for some f##ked up reason make their spindles differ on the non drive side on some of their bbs. Not sure what the point is. But hey, they are shimano!
Whether or not it is reversible depends on the threads in your BB shell and/or on the type of bb you are using. Phil wood for example are all reversible. Some cup and cone bbs you can reverse the spindle and/or cups. Usually there is no reason not to stick with the L/R specifications of the manufacturer unlell you are trying to solve some chainline or q-factor issues.
keep in mind that the shimano UN-53 and UN-52 bottom brackets are meant for road or mountain bike applications, which need to have more spindle on the drive-side in order for the chainrings to clear the frame. they could make both sides the same length, but then we'd end up with more 120mm and 124mm spindles, and wider Q-factors and more broken spindles.