Shimano 12s GRX RX820/RX822/RX610, cable pull actuation ratio 11s/12s compatibility

[DawnBat]

Will the GRX 12-speed rear derailleur work with a Shimano 12-speed mountain bike shifter?

Sorry, but the answer to that is a hard no. When we were setting up this drivetrain, I happened to have an XT shifter freshly pulled from another bike, so we tried it before hooking up the GRX levers. It took all of five shifts to realize that the pull ratio was off.

So the RX820 can't pull the M8120 RD. It's sad.
How about RX820 STI with old RX812 RD? Do they share the same pull ratio? At least 11s & 12s MTB shares the same pull ratio in some components.
RX812 is from M8000 series, it's really good enough for a 2x width range cassette combo. Such as 44-28/46-30 FC by 11-42/46 CS, It actually works well.

[satanas]

Somebody needs to try the RX820 shifter + M8120 RD with a Wolftooth Tanpan 11 pulley...

https://www.wolftoothcomponents.com/products/tanpan

...this might well work, assuming Shimano haven't been ba$tards and changed the 12 speed versus 11 speed shifter actuation ratio.

[req110]

Any thoughts on when GRX Di2 12s can arrive?

[jayjay]

Any thoughts on when GRX Di2 12s can arrive?

No idea, but I wouldn't hold my breath!

[UltraMaraFun]

Hi All

Is there anything stopping me ordering the 2 x 12 speed groupset, then just ordering the 10-45 cassette, swapping out my freehub to microspline and job done?
This would be an amazing range and with close ratios, or am I missing something to enable me to run this mullet(ish) style set up.

TIA

[DawnBat]

duplicate. sorry

[DawnBat]

Hi All

Is there anything stopping me ordering the 2 x 12 speed groupset, then just ordering the 10-45 cassette, swapping out my freehub to microspline and job done?
This would be an amazing range and with close ratios, or am I missing something to enable me to run this mullet(ish) style set up.

TIA

I'm planning the same thing, but the 2x RX820 RD (105 RD with switch) only compatible with 36t, and I think it can take 40 or 42t maxmium cassette if you tighten all the B-screw, just like RD r7000 mid cage, I'm not sure the cage length of new 12s 105 RD, it's new released. : /
And the 1x RD RX822 GS/SGS is the rebrand 1x M8100 GS/SGS (not M8120 SGS) under GRX series. Many ppl said the M8100 can't compatible with the 2x.
So I'm still waiting the compatibility report with RX812 on 12s STI and RX822 on 2x. RX812 is the rebrand M8000 GS, it can compatible with 2x or 3x FC and 46t CS, even 50/51/52 tooth by modifiction.
I'm not sure the pull ratio of 12s, I have 11s FD, RD and shifter. It's really annoyed.

[DawnBat]

duplicate. sorry

[pdlpsher1]

Hi All

Is there anything stopping me ordering the 2 x 12 speed groupset, then just ordering the 10-45 cassette, swapping out my freehub to microspline and job done?
This would be an amazing range and with close ratios, or am I missing something to enable me to run this mullet(ish) style set up.

TIA

You can put a Microspline freehub on your existing hub if your hub is a MTB hub. If you put a Microspline freehub on a road hub, then your end cap to end cap distance will end up 1.85mm too short. Microspline is for MTB hubs only. MTB hubs have wider hub flange spacing to take advantage of the fact that MTB cassettes overhangs inboard as compared to 'road' cassettes. There's a rumor that a 'road' version of the Microspline is in the works. But nothing has been confirmed by Shimano yet. The second issue is that no RDs can officially support a 2x crankset and a 10-45 cassette. Maybe with some heavy modifications one could make it work. Any volunteers?

[Upcountry]

Is there anything stopping me ordering the 2 x 12 speed groupset, then just ordering the 10-45 cassette, swapping out my freehub to microspline and job done?

I don't think there is a derailleur out there that would handle this, let alone with any kind of finesse. That's nearly 700% range! The cage would have to be able to handle something like a 52t capacity, which is way more than the pretty generous 41t capacity of the new GRX SGS rear.

[satanas]

The derailleur capacity doesn't really need to be able to handle the full theoretical range, assuming a modicum of operator skill and care. It's probably a good idea to have enough chain to (just) be able to shift into and out of big:big in case of an error, but if a few of the smallest cogs combined with the small ring lack tension it won't really matter since these aren't likely to be used and won't break anything if they are. (FWIW, there are S-Ride RDs out there that will officially handle 49T range.)

The Shimano 2x12 MTB RDs officially handle 10-45 + 10T at the front, with 38x28 rings in XTR and 36x26 in XT, however I'd be surprised if the capacity couldn't be stretched a bit. There's no way the 10-45 cassettes are "close ratio" though, unless you're comparing the lowest few gears to a 10-50 or larger MTB cassette. The largest cassette I'd be prepared to consider close ratio - in the midrange where it's most useful - is Ingrid's 44T11. After that you may as well just give up and use 1x and 10-51 or 10-52.

[DawnBat]

And it seems the rx820 shares the same design with rx812...
Maybe it's just the cage length difference.
rx812 can use the M8000 sgs cage to take on 46t cassette and use 2 by 16t tooth difference crankset simultaneously.
However we don't have 40/42 cassette at 12s, only 44t from sram, 45t from shimano and 46t from alixpress. : /

[ultimobici]

And it seems the rx820 shares the same design with rx812...
Maybe it's just the cage length difference.
rx812 can use the M8000 sgs cage to take on 46t cassette and use 2 by 16t tooth difference crankset simultaneously.
However we don't have 40/42 cassette at 12s, only 44t from sram, 45t from shimano and 46t from alixpress. : /

But it’s not. I cannot be unless the pull ratio of an 812 will work on 12 speed with just a change of lever.

As for capacity, how many times does it have to be stated? Cage length has nothing to do with capacity. It’s a combination of geometry and too jockey wheel location.


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[uilewuit]

Hi All

Is there anything stopping me ordering the 2 x 12 speed groupset, then just ordering the 10-45 cassette, swapping out my freehub to microspline and job done?
This would be an amazing range and with close ratios, or am I missing something to enable me to run this mullet(ish) style set up.

TIA

You can put a Microspline freehub on your existing hub if your hub is a MTB hub. If you put a Microspline freehub on a road hub, then your end cap to end cap distance will end up 1.85mm too short. Microspline is for MTB hubs only. MTB hubs have wider hub flange spacing to take advantage of the fact that MTB cassettes overhangs inboard as compared to 'road' cassettes. There's a rumor that a 'road' version of the Microspline is in the works. But nothing has been confirmed by Shimano yet. The second issue is that no RDs can officially support a 2x crankset and a 10-45 cassette. Maybe with some heavy modifications one could make it work. Any volunteers?

this confuses me, I was under the impression that microspline for road hubs was already a thing.
I assumed that's what this freehub body is for.
https://r2-bike.com/DT-SWISS-Freehub-Bo ... -Thru-Axle

[pdlpsher1]

I said it's not confirmed by Shimano. I didn't say it's not for sale. The availability of this freehub is quite an old news, dating back to 2022.