I’ve just bought some 11sp Ultegra levers to use 1x on my frankenbastard.
Running those, SLX cranks, and MTB BB on a Charge Plug.
I’m looking at rear mech and cassette options and am a bit confused, so:
1/ Am I correct that there’s only 1 11speed GRX mechanical rear mech (with 2 cage lengths)? The GRX 812?
And the only difference between this and the RX800 is a slightly larger capacity and slightly less weight? I’d be looking at the 812 as I’m going 1x
2/ cassettes: this one does puzzle me: a few things I’ve read say they can take both road and MTB blocks. I thought the spacing was different?
If they can take MTB, that means no issue running an xD driver for the smaller 11th, right?

Cheers!

Two mechanical mechs – one with bigger capacity for double up front and a parallelogram designed for tighter spreads (Max 34T cassette) and one with smaller capacity for 1x compatible up to 42T (though I’ve seen it work on 46T – may depend on how close hanger orientation is to Shimano’s spec).
Road and MTB sprocket spacing for MTB/road is the same, but MTB ones have narrower base and a dished big sprocket. So narrower at base but same at width at tooth height. XD 10-42 should work fine to give equivalent of 11-46 spread.

Ah, that clears it up, thanks very much!

Chainstays limit the maximum chainring size, so I’m thinking by running a 10t I’ll get a slightly higher top end 🙂

No worries. Sounds like a sensible approach.

View this post on Instagram

Purists and brand evangelists look away now. #sramforce 12 speed chain, #sramxg1150 11 speed cassette, #shimanogrx812 derailleur and classic #duraace7900 10 speed crank and narrow-wide chainring. Because #gravgrav #diyfs

A post shared by Thom (@thomthebike) on Feb 7, 2020 at 8:36am PST

Grx rd 812 works fine with 10-42 xg1150 cassette.

Cheers all.

Right, rear mech choice time.

Grx 812 is not cheap.
105 is, but obviously no clutch.
105 with eBay link extender is would seem fine for me. Bike is only used for road and towpath commuting, and will be fitted with a NW ring. Would I be daft to go 105 for less than half the cost of a true GRX mech?

Will grx 11spd 1x shifters work with apex mech and 10-42 cassette?

105 is, but obviously no clutch.
105 with eBay link extender is would seem fine for me. Bike is only used for road and towpath commuting, and will be fitted with a NW ring. Would I be daft to go 105 for less than half the cost of a true GRX mech?

Seems to me that you’ve no need of a clutch. I’m using an Ultegra rear mech on my #gradventourer and not having any problems, on or off road. That’s on a 11-40T cassette and a 50/34 compact crankset. And no extended link

Cheers, kind of confirms what I thought.
Was going to stick the single front ring on today after getting home to try it, but realised the old cranks were square taper, not HT, doh!
After doing my commute today in the big ring on the current chainset, I actually think a 36 will be fine, (it’s very flat)
It’s making sure I’ve got clearance for a large enough ring that’s the issue!