You are reading a single comment by @hippy and its replies.
Click here to read the full conversation.
-
maths
Yes, but I wanted the maths... AND the chainline of whatever mess I've bought.
Chainline is 52mm if this is to be believed:
https://bike.shimano.com/en-NA/products/components/pdp.P-FC-M8100-1.html
hippy
Yes, it's called maths. The pitch circle radius of a roller chain sprocket is very close to Pitch×Z/2π, then add 4mm to get the top of the teeth
(12.7×38/2π) +4=80.8mm, so your stays need to be 2×(chainline-4mm*) apart at a point 81mm from the BB centre
*half the ring thickness + clearance for flex