[Closed] GRX gearing with Ultegra shifters?

I'm running GRX mechs with 105 shifters and am planning on mixing and matching again on the next gravel bike.

As I recall, the only combo which doesn't work is GRX front mechs and standard chainsets.

GRX and 105 mix here too. No issues.

GRX 1x11 is funny. It's a weird cable pull that isn't shared by either road or MTB shifters. So that won't play well with others, though other forms of GRX are more chummy.

GRX shifters 1X11 with XT Di2 drive chain here. Worked a treat for the past year.

GRX 1×11 is funny.

Thanks - should add I am looking at 2x11 on the gravel to make is as bikepacking/allround friendly as possible.

Sounds like it might be worth a try and I can maybe change the shifters in due course when the world is less mad!

GRX 1×11 is funny. It’s a weird cable pull that isn’t shared by either road or MTB shifters. So that won’t play well with others, though other forms of GRX are more chummy.

Really?

Genuinely curious, I was running GRX 1x11 for long enough with 105 shifters. It usually worked fine but did seem awfully fussy, I put it down more to the long cage and a soft derailleur hanger which meant near monthly adjustments with the hanger tool...

Really?

In retrospect I may have misremembered the issue.

I knew that my GRX 1x11 setup meant that I could only use the one type of rear mech (IIRC the RD-812). But perhaps that's because it's the only roadie cable pull ratio with a big enough range to cover the GRX cassette (IIRC 11-42). The cable pull ratio means the brifters aren't compatible with MTB rear mechs.

FWIW I have no issues at all with shifting on my all GRX 1x11 setup.

Re GRX 1x11 is funny, I don’t think it’s the cable pull that’s weird it’s something like Shimano state the rear derailleur path over the cassettes is different so the 1x11 is for the larger cassettes and the 2x11 for the (relatively) smaller cassettes with 34t (maybe 36t) max recommended for the 2x11. However Shimano are always conservative with their compatibility recommendations and I’m sure I’ve seen YouTube videos using 40t cassettes with the 2x11 rear derailleur without problems and larger still with Wolftooth adapters. Hope this makes sense.

I knew that my GRX 1×11 setup meant that I could only use the one type of rear mech (IIRC the RD-812).

Ah yes, I came across that, had to upsize mech in order to run bigger cassette, although I think Scotroutes gets away with an Ultegra RX and big cassette...

smaller cassettes with 34t (maybe 36t) max recommended for the 2×11.

However there isn't anything on the Shimano website that suggests the 810 series Front-D can't be run with the larger 40t rear cassette & Rear-D. Or am I missing something re chainlines etc?

https://bike.shimano.com/en-EU/product/component/grx-11-speed/FD-RX810-F.html

If it can only be run with 34t, for now I am probably only looking at a new GRX front mech and 48/31 crankset, as I already have a 34t rear cassette with my current set up.

I’ve tried to find out where I read the reasons for the different derailleurs but can’t find it now. However there is lots of anecdotal evidence from various forums and YouTube videos that you can run larger cassettes with GRX 2x11 rear derailleurs. Another option o consider I suppose is the smaller chainrings on the GRX FC-RX600-11 crankset 46/30t but it’s only one tooth difference on the smaller ring.

I'm currently running 50/34 and 11-40 with an Ultegra RX800 rear mech. Works perfectly despite what Shimano say.

I might consider reducing chainring size via a different chainset or the Absolute Black chainrings.

GRX 1×11 is funny. It’s a weird cable pull

No it's not, it has exactly the same cable pull as GRX 2x11, 105 and Ultegra 11 speed. I've just swapped from a 810 grx mech set up 2x to a GRX812 mech set up 1x to allow me to run a 42t cassette.

The difference is in the mech tooth capacity, the 810 has a published max tooth count (cassette) of 34t but it will run a 36t if your hanger allows for clearance, it does however have the ability to run with a 30/46 front set up with ease.

The 812 rear mech will run a published 42t cassette, but can't deal with the chain capacity to run a double.

GRX 1×11 is funny. It’s a weird cable pull

You may be thinking of the GRX400 10-speed groupset, which is mostly incompatible with other 10-speed Shimano rear mechs shifters bar the latest Tiagra I think, as it uses the same pull ratio as 11-speed.

Thanks all. Looks like it will be much easier and cheaper to get lowers gears than I expected. Will get some GRX shifters in due course (as I think the shape makes a lot of sense on the gravel bike).

Nothing weird about the cable pull ratios of any GRX mechs compared to similar era road mechs.

They're a bit more expensive, but Sugino OX cranks are pretty good and you can get them down to 44/30. Which is what I've been running for the last 5 years with Red eTap HRD with no problems.

Managed to source a XT 11-40 cassette locally and with only some adjustment of the B tension on my Ultegra long cage, from a short spin round the block appears to work very well. Bought a new chain but old one only had 700 miles on it and so far it doesn’t seem it’s needed.

Gives me 34-40 and already feels a big difference. We’ll see how the old HR finds it.

Thanks ever knowledgeable STW

Oh ye of little faith...

😂

Mega lol

I'm running very old 105 hydraulic shifters with deore calipers and a grx rear mech and an XT chainset with 11-46 cassette & KMC chain. All works perfectly together

As for tooth capacity I'm running the 1x 800 series rear mech with a 11-51 cassette and 40t chainring

GRX with Ultegra Shifters & Hope RX4 Calipers here - work perfectly.