Asymmetrical spindle and new BB
I'm beginning to shop for parts for my winter project (an 82 Trek 614 with a triple) and was considering swapping in a UN-55 since the races of the old BB are in rough shape (and may do the same on my wife's Trek). I've read the threads about sizing and still I'm not sure I have it straight. The old spindle is an asymmetrical one, stamped "3U" and has the exact dimensions listed in Sheldon's table - 124.5 overall length, 32 non-drive side, 40.5 drive side. In the market, I'm seeing only 122.5 and 127 as choices in the UN-55. Can those of you who have swapped in lots of these on 68mm shells with a triple crank point the way for me a little bit? I think one of the things I'm missing is the logic of how spacers are used (these are also mentioned in Sheldon's table). I know I should've measured the chainline to the middle ring before I broke the bike down, but it slipped my mind. Anyway, the LBS told me 127 for my case, and another guy whose opinion I trust told me 122.5. Maybe this is one of those things that becomes obvious to you when you actually do it?