Originally Posted by
Sterkoff
This appears to be exactly the reply I needed to expand my thinking on this and send me in a useful direction. Thank you!
Originally Posted by
Sterkoff
Thinking about this further.. As a beginner, I think I should try to figure it out using the methods you recommend but perhaps the safest path forward would be to temporarily install everything using my existing 73x118 BB, see where outer vs middle ring location land comparatively and then purchase a new BB with the spindle length based on what will get me closest to cassette centerline? I am not in any hurry.
You're welcome.
Yes, testing the FC-M361 on the 118mm BB will give you some idea of what crankarm/chainring clearance will be at the chainstays. The 118mm BB is normally symmetrical (or close) and the 122 isn't. You can probably expect the rings to be about 3mm closer to the frame than the 'spec' #s posted earlier. The next common shorter size is 115mm and should be symmetrical (or close).
FYI, the radius of the chainring changes at about 2mm per tooth difference.
It's always hard to guess what is possible since frame chainstays all have different bends. Only by fitting and estimating will it be possible to see what could work.