Originally Posted by
tFUnK
I've gone 32t on a RD rated for 28t max, but that's not the same as going from 36t to 40t. That said, if running 1x, an extender like the WT should get it to clear the large cog, and since it's 1x you won't run into chain wrap capacity issues. I do this with a RD rated for 32t and run an extender to clear my 40t cassette.
That's exactly the kind of information I needed. Thanks very much. If you made the jump from 32 to 40 with a WT device, I believe I can go from 36 to 42 with a similar gizmo. I'd be satisfied with 11-40, but Shimano seems to skip the 40 in 10 speed, leaving the next choice to be 42 or 46, if I go with the Shimano brand, which I prefer.