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https://www.reddit.com/r/gravelcycling/comments/e6luiw/ultegra_rx_vs_grx_rear_deraileur_what_gives/
42T
https://bike.shimano.com/en-US/product/component/grx-11-speed/RD-RX812.html34T
https://bike.shimano.com/en-US/product/component/grx-11-speed/RD-RX810.htmlShimano GRX RD-RX815 Di2 rear derailleur is a combination of the Shimano Ultegra RX rear derailleur and a Shimano mountain bike rear derailleur. It features a slim Shadow profile and clutch mechanism but has a slightly stronger clutch compared to Ultegra RX. It is also very slightly heavier than Ultegra RX, but the overall quality matches that of Shimano Ultegra. The Shimano GRX RD-RX812 rear derailleur is 1x-specific
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Thanks, i saw the diff capacities on the two GRX derailleurs; I'm not looking to drop the front mech so I think the 812 doesn't officially work...
Tempted to try the 810 because what's the worst that can happen Vs buying a normal ultegra?
That said I should probably make sure I have a frame to put it on first, hopefully the mason is still useable despite its troubles
...so the next Q is whether the GRX would be more resistant to knocks!
Shimano blurb suggests it's further swung under the cassette so should be safer. In theory....