Originally Posted by
misctrader
I was hit, mildly, by a car and fell over on the right side of the bike and the crank arm broke off along with the spindle tip.
So the SR Super Custom would be a new crank or is it the existing crank and you were able to extract the portion of the spindle that broke?
If you can salvage the crankset, as @
due ruote said, measure the existing spindle - try total length minus the threaded (male) portion of the spindle, if there is one. That will give you a starting point.
If asymmetrical ( drive side different distance from race to end than non-drive side - which is likely on these Treks), see this
https://www.sheldonbrown.com/bbsize.html
Scroll down to where the diagram of the spindle is, with the table below. That should bring you home.
Not much downside being wrong here, ultimately you will probably use the other one some day. I usually start out wider (127) and see how the bike shifts. Too close in and either the smallest front chainring rubs on the frame or you will get chainrub on the middle front chainring when on the smallest front chainring and are in the middle rear cogs.
You could also try to figure out chainline, but I'm an engineer and can't figure it out reliably - I just do trial and error (hence a drawer full of different spindles)