As per title, going from 2×10 (38 tooth outer) to 3×10 (24-34-42).shimano, how many additonal chain links do i need on my new chain over the original?

I’d go for one extra inner and one extra outer plate. Logic being half of 42 minus half of 38. Might be worth measuring it properly tho.

Well the general measure is to wrap chain around the 2 largest gears. Assuming rear stays the same you would need to account for 4 extra teeth so 4 links more

The chain only wraps round half the ring hence I reckon you only need to account for 2 extra teeth. Not saying I’m right but that’s my opinion.

Also going from 36 max to 34 max on rear… xt clutch mech if that makes a difference.

@ Lazy Mike

Hmm, makes sense when you put it like that. ❓

Easy to check since the chain will be split anyway!