Shimano GRX 12 speed - what we got, vs. what was expected

Shimano has finally announced a long-awaited 12 speed version ("GRX RX820 series") of their GRX groupset. GRX had previously been stuck in 11 speed limbo, while Shimano's high-end road (Dura-Ace, Ultegra, 105) and MTB (XTR, XT, etc.) had all moved on to 12 speed already.

The GRX components are designed for off-road riding on bikes with drop handlebars - think cyclocross and gravel - and have been an industry favorite, but they were getting long in the tooth. Previously, I touched on what riders might want from the then-unreleased 12 speed GRX group. Release of a 12 speed version was inevitable, we just didn't know when.

Now that the cat is out of the bag, let's take a look at what we got, versus what was predicated or desired.

The new GRX will be 12 speed

Yes, that wasn't a tough prediction. 12 speed GRX prototypes were spotted being tested at the Unbound Gravel earlier this Summer, so expecting the new group to go 12 speed wasn't exactly a big risk.

GRX 12 speed is mechanical shifting only (for now)

Shimano did not release a 12 speed GRX Di2 version with electronic, wireless shifting modeled after the 12 speed Dura-Ace and Ultegra road groups, which are now Di2 only. This was unexpected.

Instead, for the time being, that updated 12 speed GRX group is mechanical shifting only. Didn't see that one coming...

Surely, there is also a 12 speed Di2 group in the hopper, which must not quite be ready yet. It would likely use the same brake calipers, cranksets, chains, and cassettes, but electronic Di2 shifter/brake levers and derailleurs. We actually saw this in reverse with the 12 speed 105 group, which first appeared on the market as Di2 only (to the horror of some traditionalists), but a mechanical version was later released. 

What about Microspline?

Something I wasn't anticipating was GRX 12 speed moving to the Microspline-style freehub body. 1st-gen GRX 11 speed was always more "road" than "MTB", and I thought it would continue to use the classic style, HG freehub body, as the 12 speed road groups do.

That turned out to be inaccurate, and 12 speed GRX now leverages the Microspline setup to offer a 10 tooth cog that wasn't possible on the 11 speed setups.

12 speed GRX will have bigger cassettes and a rear derailleur with more capacity

Survey says: true. SRAM was eating Shimano's lunch with 1x, single chainring, mega-range cassette for years. With a 12 speed GRX now compatible with 10-45 and 10-51 teeth options, that's no longer the case. There's no "GRX" cassette, the 12 speed GRX series uses Shimano's SLX, XT, and XTR mountain bike cassettes.

There's also an 11-36 option for 2x12 double chainring bikes, which is 2 teeth lower than the previous 34 tooth largest cog on GRX 11 speed. So, Shimano did in fact deliver the lower gears riders wanted, whether you ride a double or 1x, you now have lower gear options on GRX 12 speed. This is great for older, less fit riders, loaded touring, bikepacking, and very steep terrain. Or you can also continue to use an 11-34, 12 speed cassette if you prefer.

Another nice touch is the ability to swap rear derailleur cages between the various GRX 12 speed rear derailleurs. There are different options, depending on which cassette you choose. That wasn't possible with the old 11 speed gear, you needed an entirely new rear derailleur if you wanted to switch.

It's worth noting all those lower gears happen through the cassette and rear derailleur - the chainring ratios offered, 46-30T and 48-31T "subcompact" rings, remain the same, just updated with a shape for the 12 speed chains.

New GRX wheelset, "WH-RX880"

Somewhat predictably, there's a new GRX wheelset to go with the new 12 speed components. It uses the Microspline freehub to support those new MTB-style cassettes, 25mm width carbon rim to better support wider gravel tires, and is tubeless-ready.

What about mixing and matching 12 speed GRX with Shimano's MTB line?

Other than the cassettes previously mentioned, that's a no. Don't expect to sub in a 12 speed mountain bike rear derailleur with your GRX shifter, nor the reverse.

That's true of the 12 speed mechanical GRX, and also unlikely to change in the event a future 12 speed GRX Di2 group is released.

Silver components

Shimano created a GRX RX810 11 speed "Limited" group in polished silver aluminum instead of black that was offered for sale for a limited time. That option goes away with the "back to black" GRX 12 speed announced today. No silver parts on the horizon.

New crankset? Sort of

The new GRX 12 speed cranks appear identical to the old 11 speed models, just with new chainrings for 12 speed compatibilitly. So if you're already a GRX 11 speed owner looking to upgrade, there's a path on the crankset, by swapping out the rings. 

This also means that 3rd-party chainring manufacturers, like Wolf Tooth Components, will probably be quick to market with new aftermarket, 12 speed compatible chainrings that fit those same GRX cranks. Especially on the 1x side, this could create opportunities for even lower gearing than what Shimano offers.

There's also an RX-600 12 speed version, too

GRX 11 speed came in two series, a higher-end 800 and a lower-end 600. They were broadly compatible for interchanging parts.

In addition to the new 820-series 12 speed parts, the 600-series GRX is getting a bump to 12 speed as well. That means there is an economical option that some riders might prefer for dollar savings - on the crankset, for example.

Back to blog