I currently run a GRX (812) set up on my Fearless Warlock.
I recently swapped to an Ultegra 11/34 cassette as living where I do doesn't require anything more!
Shifting is fine but I'm sure I read that the GRX mech isn't designed for such a small cassette.
I had considered an Ultegra RX mech but they seem fairly rare.
Soooooo do I keep things as they are and cross fingers and toes that everything continues to play ball or try an dfind an Ultegra RX rear mech?
11-34 isn't small. It will be fine. Maybe shorten chain if needed.
GRX810 mech is specifically for 2x with 11-32/34.
I had a Classified 2x hub set up with 1x ring and the Classified 11-34 cassette - should have worked with the 810, but didn't. 812 with B-tension wound out worked great.
So, if 2x, RD-RX810 is the answer, if 1x, stick with the 812 and back off your B-tension in order for guide pulley to track more closely across the cassette.
I’d stick it’s the GRX. It’s worked fine with that cassette on 2X
The RX812 Mech is intended for 1x11 (11-42+ basically) while the RX810 version is for 2x11 with a ~11-36 or 11-34 cassette (Allegedly it'll do up to 11-40, but not according to shimano).
I only have one mate who's using the Ultegra RX mech (on 2x11), It came on his bike, He likes it and sees no reason to change, but if he were needing a replacement rear mech He'd probably go for a GRX RX810 just to have some broader cassette options and 11-34 is the top of it's (published) range.
Having said all of that, there's no real reason why the RX812 won't work with a smaller cassette, an 11-34 is hardly stretching it's capacity, just adjust it to suit.
I thought Ultegra RX was the forerunner of GRX 800. Did I get that wrong?
I have an Ultegra RX rear mech from 2019, and I don’t remember GRX then.
I thought Ultegra RX was the forerunner of GRX 800. Did I get that wrong?
No you are correct, it was a bit of an in-between group and aimed more at CX racing than Gravel, basically it's just a long cage Ultegra mech with a clutch, it's not really designed to stretch to wider cassettes, the GRX mechs were all fresh tooling...
