Originally Posted by
Loose_head
Using the capacity formula, the biggest cassette is 11 - 36 to get 41t, is that correct?
Yes.
So I can't go more than the official spec and stay 2x?
The official spec also has a max cog size limit of 36T, so it's not like you dodge the issue even if you go 1x.
That said, plenty of people violate these specs without that much trouble. I know a few people running 11-42 cassettes on GRX400 or GRX810 derailleurs with 16-tooth front differences. If you exceed the max cog rating, you'll potentially want to get a Wolf Tooth RoadLink DM. You'll also need to use a longer chain, or else shifting into the big-big region of the drivetrain may damage the bike (note that because you're exceeding chain wrap, this will likely make the chain go slack in the small-small region, so you'll have extra reason to avoid small-small cross-chaining).