Just finished my first retro build (will do a thread soon), a '90 marin palisades 1x8 rat. Built it up with M730 to M739 XT parts plus existing good bits and some new parts.
I used a 122.5mm BB as recommended by Shelton brown for the M730 crank arms I used. However as I only have one chainring and it's in the outer position, I'm thinking the front chain line distance is too large. I measured it today and it's about 55mm from centre of seat tube to centre of chain. I've had the chain come off once when shifting quickly through the cassette (from 11t towards 32t) and my thought is that this could be the long chain line distance coupled with the small diameter 34t outer chainring?
Should I get a shorter bb?
I used a 122.5mm BB as recommended by Shelton brown for the M730 crank arms I used. However as I only have one chainring and it's in the outer position, I'm thinking the front chain line distance is too large. I measured it today and it's about 55mm from centre of seat tube to centre of chain. I've had the chain come off once when shifting quickly through the cassette (from 11t towards 32t) and my thought is that this could be the long chain line distance coupled with the small diameter 34t outer chainring?
Should I get a shorter bb?