Originally Posted by
BoozyMcliverRot
Put the BB back in the frame and install the crankset. Measure the distance between the chainring and chainstay. Muliply that distance by 2 and subtract 8mm(4mm each side) then get a symmetrical BB that much shorter than the current BB. Or you could just find out the correct BB length for that praticular crankset and get that size.
Edit: measure the distance between crankarm where the pedal mounts and the chainstay,not the chainring.
I can't mock it up. The BB is JIS, the Super Mighty cranks are ISO. If I tried to bolt it up it would ruin the crank (and supposedly stick out 4.5mm from where the last crank sat). I did try, I gave the nut a few turns and it didn't feel right so I stopped.
Edit: I suppose I could put the old Super Maxy back in, but would that directly relate to the Super Mighty?
I believe I now know what I need; 68mm shell, 125mm+ spindle, English thread, ISO taper. I'm out of my wheelhouse here, but I've searched pretty well and can't find anything worth using with those specs.