Hi Jay, here's my take on the GRX RX-810 derailer - it solved all my shifting and hard pedaling problems though it's not rapid rise.
On my Charlie I've used the Nexave RD-C600 Rapid rise and XT rapid rise derailers with this up to this point and they just skipped gears every time I pushed real hard with my 46/30 double and 11-40t cassette. This GRX RX810 is simply solid in comparison - I can't make it skip gears even if I try by pedaling hard as I can uphill while in too high a gear. I'm not sure if it's the clutch or a stronger spring (since it seems just as solid without the clutch switched on). I miss the rapid rise function, but solid shifting and pedaling were not possible for me with other derailers where 45t of chain wrap capacity is needed. The RX810 says it maxes out at 34t low on the cassette, but I'm running it on a 40t cassette with plenty of room to adjust the b-screw still. It also says it has max 40t wrap capacity but clearly can exceed that without issues.
My Charlie has the following drivetrain setup:
Rear derailer: RX810
Front derailer: Shimano Claris double R2000 (IIRC on the model number - the one Will recommended in a Riv email at some point)
Cassette: 11-40t 10 speed Sunrace
Crankset: IRD Compact 46/30t 172.5mm (like the IRD Defiant and VO double, but a variant from Boulder Bicycle that is cheaper)
Shifters: Silver2 thumbies with the range limiting washer filed off
Wheels: SP PV-8 hub in front, VO casette silver hub in back; 32h, DT Swiss Competition double butted spokes, VO Voyager rims, Rene Herse Snoqualmie Pass (44x700) endurance tires.
The only down side I can think of is that I need to push a bit harder with my fingers when shifting - maybe I could back the d-ring screw out a little and solve this, but without a drop of blue loctite I figure a little extra tightness is fine.
There is not much extra range on the shifter but it has enough so there's extra on both the high and low sides of the cassette.
Abe
