GRX rear mech compatibility with road shifters.

[iandusud]

This isn't answering your original question but if you're looking for lower gears and have 5700 10speed levers at the moment I would suggest that you stick with what you have and use a triple chainset along with an 11-36 cassette. If you use a GS rear mech it although it is only rated to 32 largest sprocket it will probably cope with 36 and it will definitely cope with 36 if you fit a hanger extender. On our tandem we run a triple with 26 39 50 chainrings and 11-36 on the rear using a Tiagra 4700gs rear mech with hanger extender. The rear mech doesn't have enough capacity for the system but in practice this is not a problem. I run the chain long enough so that I can run 50/36. This means that if I'm on the small chainring the chain with be slack on the smaller sprockets which is not a problem and in practice I only ever use the small chainring on the 4 or five largest sprockets. If you run a double chainset you will have a big jump between in gears changing chainrings. A triple will also give you a better chainline more of the time.

[ElCani]

This isn't answering your original question but if you're looking for lower gears and have 5700 10speed levers at the moment I would suggest that you stick with what you have and use a triple chainset along with an 11-36 cassette. If you use a GS rear mech it although it is only rated to 32 largest sprocket it will probably cope with 36 and it will definitely cope with 36 if you fit a hanger extender. On our tandem we run a triple with 26 39 50 chainrings and 11-36 on the rear using a Tiagra 4700gs rear mech with hanger extender. The rear mech doesn't have enough capacity for the system but in practice this is not a problem. I run the chain long enough so that I can run 50/36. This means that if I'm on the small chainring the chain with be slack on the smaller sprockets which is not a problem and in practice I only ever use the small chainring on the 4 or five largest sprockets. If you run a double chainset you will have a big jump between in gears changing chainrings. A triple will also give you a better chainline more of the time.

Don’t forget that to do this would require a new LH shifter, assuming the current one is a double.

[Barry and Janet wil]

Thanks for all of the tips guys.
The plan is R7000 RH shifter, existing LH operates the 22-34-46 chainrings. An R7000 rear derailer and a hanger extender when the 11-36 is fitted. I'll normally have 11-30 fitted as that's fine for our Lincolnshire hills.
Once again, thanks folks.

I'm a trendy consumer. Just look at my SM-G950F using hovercraft full of eels.

[iandusud]

Thanks for all of the tips guys.
The plan is R7000 RH shifter, existing LH operates the 22-34-46 chainrings. An R7000 rear derailer and a hanger extender when the 11-36 is fitted. I'll normally have 11-30 fitted as that's fine for our Lincolnshire hills.
Once again, thanks folks.

I'm a trendy consumer. Just look at my SM-G950F using hovercraft full of eels.

Sounds like a good set up to me. 22/30 should be low enough for anything for an unloaded tandem. 22/36 would be great for loaded touring. I would suggest that you might get away without the hanger extender with the 36 depending on the geometry of your existing hanger. Shimano are very conservative with their specs for rear derailleurs. I have a road bike running a 32 sprocket with a short Ultegra rear mech designed for max 28. However if you do fit the 11-36 don't forget to carefully check the chain length. You will probably need a longer chain.

Ian