Figuring this stuff out is part of the fun, and the only reason that I bought the bike, er, box of parts. I have been to one bike store with less than stellar results, the guy I talked to had less of a clue about bikes than I do.

If I find a BB that is listed as "Bottom Bracket, 68 73 x 113mm", I think that I understand that it will fit in a 68 or 73mm bottom bracket, but what does the 113mm indicate? Is it the space between the crank arms? Or is it the length of the shaft?