Also guess I need a 42 inner ring? Or can I run a 39?
You might get away with a 39T, but the recommended maximum gap is 16T, so a 40T would be safe. Make sure your RD has enough capacity if you're going to exploit the maximum difference up front.
Thanks.
@skinny started
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You might get away with a 39T, but the recommended maximum gap is 16T, so a 40T would be safe. Make sure your RD has enough capacity if you're going to exploit the maximum difference up front.