A new 12-speed Shimano GRX groupset has been spotted at Unbound 2023.
The pictured groupset is mechanical and built around a 10-45t XTR M9100 cassette. Thus far, we’ve only seen a 1x build.
The groupset was fitted to the bike of Shimano-sponsored Taylor Lideen, who rode Unbound XL this weekend – a brutal 350-mile version of the season’s biggest gravel race, starting the night before the 200-mile main event.
Here’s everything we know so far about 12-speed Shimano GRX – and some questions that are left unanswered.
Wide-range 10-45t cassette tells a larger story
The groupset pictured is paired with a 10-45t 12-speed XTR M9100 mountain bike cassette.
This signifies three big changes for Shimano GRX.
1) 12-speed takeover
The key change is the move to 12-speed from 11-speed.
This brings Shimano GRX in line with the brand’s road and mountain bike groupsets.
It also brings GRX closer to its competitors – SRAM’s gravel-specific XPLR groupsets have been 12-speed from the off, with Campagnolo going one step further at 13-speed for its radical Ekar groupset.
2) Bigger cassettes
The 10-45t cassette also tells us Shimano is increasing the capacity of its 1x GRX derailleurs.
Current GRX groupsets top out at 42t for a 1x setup.
The shift to a 10t small cog (more on that in a second) and 45t large cog will result in a significantly larger gear range (450 per cent vs 381 per cent) for 1x riders.
That brings Shimano closer to its rivals, who have more openly embraced 1x drivetrains for gravel riding.
SRAM XPLR uses a maximum 10-44t cassette, so Shimano betters its main rival by 1-tooth here. Campagnolo Ekar offers 9-36t, 9-42t and 10-44t cassette options.
Riders seeking even greater range also have the option of speccing a mullet drivetrain with SRAM, with the possibility of running a monstrous 10-52t dinner plate.
Micro Spline for gravel
Finally, speccing a mountain bike cassette confirms Shimano will use its Micro Spline freehub standard for the next generation of GRX.
Introduced on the brand’s 12-speed mountain bike groupsets, Micro Spline permits the use of a 10t small sprocket.
Shimano’s longstanding Hyperglide freehub standard – which the previous-generation GRX used – had a minimum 11t cog.
The XTR cassette also features Shimano’s Hyperglide+ technology, which would be a first for GRX.
Hyperglide+ sees the sprockets on the cassette formed to help smoothly guide the chain when shifting into a harder gear.
Like Micro Spline, this debuted on Shimano’s mountain bike groupsets but has since been ported over to the road with Dura-Ace R9200 and Ultegra R8100.
Subtly different calipers may give away naming conventions
The brake calipers have been updated in a similar fashion to Shimano’s latest road bike groupsets, shifting the bleed port to the outside face of the body.
Looking back now, we’ve realised the new design caliper actually quietly debuted with the release of Shimano’s handsome polished silver GRX Limited groupset.
The GRX Limited calipers are given the product code BR-RX820-LE.
Assuming the rest of the groupset follows Shimano’s typical naming conventions, 12-speed mechanical GRX will likely live under the RX820 family.
Is that you, M6100?
The new 12-speed Shimano GRX rear derailleur is visually very similar to the existing Deore M6100 mountain bike rear derailleur.
The overall shape is similar and, in keeping with Shimano’s 12-speed mountain bike groupsets, 12-speed GRX does away with the B-link.
This small alloy plate sat between the upper knuckle of the rear derailleur and the derailleur hanger.
Though rarely seen, this could be removed and replaced with a specially-designed direct-mount hanger on certain frames.
The B-link was present on the previous generation of GRX and is still seen on Shimano’s latest road groupsets.
The finish on the parallelogram plates is now more matte and the pulleys are slightly larger. The pulley cage has also been redesigned.
A clutch is still in place, though the switch to control this has a slightly different design, with a larger lever that sits behind the clutch itself.
Business as usual for cranks and shifters
At first glance, the crankset looks very similar, if not identical to the existing, GRX R810 crankset.
The key difference is, of course, a switch to 12-speed 1x chainring.
Though this retains Shimano’s familiar narrow-wide tooth pattern, we expect the design of this will have been modified to accommodate a narrower 12-speed chain.
The shifters look identical to the current design, though the internals will have been updated for the upgrade to 12-speed.
This will be the first mechanical 12-speed drop bar shifter from Shimano, which could be a more significant development than it appears at first glance.
Since the move to 10-speed, Shimano has used different cable pull ratios for its road and mountain bike groupsets.
This has meant it is not possible to create a so-called mullet setup with mechanical Shimano components.
A mullet drivetrain pairs drop-bar shifters with a mountain bike rear derailleur, offering a huge gear range for a 1x setup.
These setups have grown in popularity in recent years, notably with SRAM riders.
Could Shimano GRX 12-speed use the same cable pull ratio as the brand’s 12-speed mountain bike components, making a much-dreamed-about Shimano mullet drivetrain a possibility?
It’s impossible to tell from the photos but our fingers are crossed.
Di2? 2x?
While there’s lots to digest already, this early preview still leaves us with some key questions – principally, will Shimano continue to offer 2x and Di2 versions of GRX?
Given the popularity of its existing double-chainring gravel groupsets and Shimano’s commitment to 2x groupsets for road cycling, we think the former is almost a certainty.
Only Campagnolo, with its radical 13-speed Ekar groupset, has gone all-out committing to 1x groupsets alone for gravel bikes.
It’s almost a certainty that Shimano will also continue to offer a Di2 version of GRX.
Though Shimano hasn’t updated its Di2 electronic mountain bike groupsets for some time, it has continued to invest on the road side, bringing Di2 right down to its third-tier 105 level.
11-speed GRX was only available in a single top-tier Di2 option. Could we see Shimano follow its road bike groupsets and offer lower-priced Di2 options? We can’t wait to find out.
