Originally Posted by
drtyrrel
Thank you everybody. I do have the axle that came with the triple crank. I'll try that first to get an idea of the length I need. Should the distance from the downtube center to the center of the middle chain ring line up with the middle of the rear derailleur?
If you have the original BB axle from your triple, measure it end to end and obtain a UN-26 or other BB cartridge of the approximately the same length. Better to be 1-3 millimetrs wide than too short.
Good luck.