[Closed] RX800 11 speed rear mech / GRX600 1x compatibility

Will work fine

Cheers, Simon !

Shimano site always useful for compatibility info...

https://productinfo.shimano.com/#/com/?cid=C-453&acid=C-454

that compatibility chart is a little misleading in that it suggests that there is such a thing as a 1x specific mech and a 2x specific mech, or that 2x levers won't work with a 1x setup. It also doesn't show that the newer (4700 onwards) 10 speed RDs will work with 11spd levers and cassettes.

There is such a thing as specific 1x and 2x GRX mechs. 2x has a more traditional parallelogram orientation to track across closer spread cassettes (36T max) but has greater capacity to cope with the additional tooth difference up front. 1x has a parallelogram designed to work with wider spreads (up to 42T) but with a smaller capacity as it doesn't need to deal with front chainring differences.

Optimised maybe but not specific. You could run either mech with a single or double provided the capacity and range matched your gearing choice

They are specifically designed to work with each set up. The double would work perfectly on a 1x 11-34 cassette, but not perfectly on an 11-42. Few people would want to run 1x 11-34 outside CX racing. The 1x mech is unlikely to have sufficient capacity for a double due to its shorter cage.

The mechs are very different - not just cage length differences. Not sure how much more specific you want them to be. 810 double has a 40T capacity, and the 812 1x version only has a capacity of 31T as that’s all it needs for its purpose.

I want it to run on a cross bike 1x set-up

I know there is a specific GRX 810 rear mech but for a max 32T rear, they recommend a Medium cage - unable to find one, hence why I was asking about the RX option

There’s only one cage option - it’ll be bigger than you need but will work fine on 11-32. Either 800 or 810 would be best. 812 recommended only for 11-40/42T.