I just bought an older Trek (lugged steel) from a garage sale, and it needs some major work. It currently has a triple chainring, but two of the chainrings are missing some teeth and the bottom bracket has a nasty wobble. I thought I'd just install a double crankset and buy a new bottom bracket.
What length BB spindle do I need for a double crankset? This is something I haven't had enough experience with to fully understand -- is this something that's regulated, or is it different from bike to bike? Can I always use x-length with doubles and x-length with triples? Is it something specified by the bike manufacturer, or the crank manufacturer?