Originally Posted by TimothyH

I don't know about GRX compatibility but an 11-42 cassette will work with 7000 and 8000 series GS rear derailleurs if 46/30 rings are used up front. I'm running this exact setup now.

A 1.85 mm spacer is required behind the mountain bike cassette so that it fits a road freehub. An entire 116 link chain is needed. No Wolftooth is used. Low gear with 38 mm tires is 19.5 inches.

I was running an 11/36 cassette with Ultegra 50/36 compact road cranks. That was fine for racing but not for bikepacking where the bike has 25 to 35 lb extra gear.

Even apart from bikepacking, my legs are happier now. North Georgia is very rugged terrain and every ride has climbs 10% or more. I regularly do climbs up to 16%. Sometimes I'll be climbing for an hour straight. The lower gearing of the 11/42 cassette allows me to use the middle range of gears where I would have been in the lowest gear grinding it out with the previous or stock setup.

There are at least two others I ride with in North Georgia who run gravel bikes with 11-42 XT cassettes and 46/30 rings. On just completed Dirty Kanza with this setup.

Stability at low speeds isn't an issue. On the contrary. 45 minutes into a 1.5 hour long climb and the lower gears are a Godsend.


-Tim-