New Shimano GRX adds wide range 12-speed gearing, uses Microspline freehub

The Shimano GRX gravel groupset is updated to 12-speed gearing with new brakes, derailleurs, and ergonomics. Like the previous-generation GRX, this new version of Shimano GRX 12-speed takes the best of their road drivetrains and their MTB drivetrains to make what they say “hits the heart of the gravel bike market.”

As before, there is a choice of 1x and 2x drivetrain options. 1x cassettes are now shared with Shimano’s mountain bike drivetrains, while the 2x cassettes come from Shimano Ultegra and 105 drivetrains. In addition, Shimano has released a new gravel-specific wheelset that not only comes with market-competitive dimensions (width, depth) but are also reasonably lightweight for their price, too.

We’ve had the chance to put in a few good rides on the new 1x drivetrain; see our Shimano GRX review here.

Quick hits: 7 things to know about the new Shimano GRX

• Shimano GRX is now available with a 12-speed drivetrain option to replace the outgoing 11-speed mechanical drivetrains.
• 1x drivetrains are available with a 10-45t or 10-51t cassette options shared with 12-speed Shimano MTB. Available 1x chainrings range from 38T to 42T depending on crank choice.
• On that note, the cranks are the same between GRX 11 speed and 12 speed; only the chainrings are different.
• Existing 12-speed Shimano chains are compatible with the new GRX 12-speed
• A new Shimano GRX RX-820 lever has been redesigned at the lever body for greater comfort with flared drop bars.
• 1x drivetrains have the option for integrated dropper post compatibility as before.
• Complete groupsets are said to be available at launch, but Shimano is unsure about complete bikes with their drivetrain.

What’s new with Shimano GRX

Our first look at Shimano GRX 12 speed was at Unbound Gravel 2023, where Taylor Lideen was aboard a Pivot Vault with GRX 1x. We were initially surprised to see how little had changed visually, but the updates seemed to amount to a new derailleur, cassette, and chainring. It turns out there was a bit more to what’s going on under the hood of this latest generation of GRX.

The most obvious change for GRX 12-speed is with gearing. GRX is still available with 1x and 2x drivetrains, but there are more options now than before.

1x drivetrains receive the option of a 10-45t or a 10-51t cassette, both of which are shared with Shimano’s MTB groups. That means GRX uses the same 12-speed chains as every other 12-speed Shimano drivetrain from road or mountain. It also means, however, that using their new cassettes requires the use of a Shimano Microspline freehub.

Shimano’s road and gravel cassettes until this point have used some variation on their HG freehub, the original design of which dates back to 1978.

The Shimano GRX 2x cassette options have been updated as well. An 11-34t and a new 11-36t cassette are brought over from Shimano 105 and Ultegra drivetrains. These cassettes are compatible with Shimano HG road freehubs as well as their newer HG L2 freehub found on some of their new 12-speed wheels.

Chainring options still include a range of 38 to 42T 1x chainrings, and a choice of 48-31T or 46-30T 2x chainrings depending on what grade of crankset you go with. Chainrings are swappable between crank arms, allowing riders to keep their cranks and go between 1x and 2x according to their needs.

Matching the gearing is a set of three new derailleurs, two for 1x and one for 2x drivetrains. All derailleurs still use the Shadow RD+ clutch design that is serviceable for long-term durability. The GS derailleur is optimized for the 1x 10-45t cassette, while the SGS derailleur is optimized for the 1x 10-51t cassette. This 1x strategy falls in line with Shimano’s mountain bike derailleurs which are optimized for the cassette’s specific gearing profiles.

Shimano GRX 2x continues with one derailleur for both 11-34t and 11-36t cassettes. It shares the same cage lengths as the newly-released Shimano 105 mechanical drivetrain but adds Shimano’s clutch design. Both derailleurs use a cable pull unique to Shimano’s 12-speed mechanical drop bar lineup and are different from 11-speed and Shimano MTB.

Check out our Shimano GRX first ride review for more details on the differences between 1x derailleurs.

While GRX 11-speed levers were largely based on Ultegra 11-speed mechanical levers, this latest generation is updated according to the ways riders used the brake levers, namely with flared drop handlebars.

Gravel bars with a 16 or 20-degree flare at the drop bars tended to turn out the brake levers, making them less comfortable for some at the hoods. This new RX820 lever is optimized for 16-degree flared bars. Further, the interface between the bar and hood is said to reduce pressure points to relax wrist angles.

Shimano has also made a bit deal of updating the ribbing heights for improved comfort without introducing pressure points. Previous hoods used a 0.5 mm ribbing, but the new hoods offer a 0.8 mm-tall textured ribbing along the levers.

Finally, Shimano has updated the brakes of the GRX RX820. The calipers themselves have been around for about a year or so, first seen on the polished alloy limited edition GRX group. However, according to Shimano, the new brake calipers offer 10 percent more pad clearance, resulting in less brake rub and easier brake setup.

There are also a pair of new brake rotors available shared with the rest of the Shimano road and mountain lineups. The brake rotors use an updated aluminum carrier that is said to make them more heat resistant. The result is less of that ting-ting-ting you might hear after heavier braking.

What hasn’t changed

GRX borrows quite a bit from other parts of Shimano’s lineup. As mentioned, cassettes come from road and MTB, chains, and brake rotors are shared across Shimano’s lineup. But there is a somewhat surprising amount that carries over from the previous generation of GRX.

The most obvious carryover is the cranks. GRX 820 and GRX 620 series cranks carry over from the previous GRX, with only the chainrings being updated for 12-speed compatibility. You’ll even see it on the cranks, as they’re now labeled GRX810/820.

GRX 620 12-speed shifters are fundamentally the same as the 11-speed version of the shifters, with only the hoods updated with ergonomic ribbing. According to Shimano, the new hoods for RX-620 are compatible with older 11-speed levers.

GRX RX-820 brake blade is carried over from GRX RX-810, including the scalloping and lever blade finish originally developed for Shimano’s fishing reels.

Shimano GRX RX400 10-speed carries on with a 2x drivetrain option. And like other gravel wheelsets, all GRX drivetrains feature a chain line optimized not for road but for wider gravel tires.

What’s the difference between GRX RX820, RX620, and RX400?

As before, Shimano GRX 800 series is the top tier of the Japanese brand’s gravel wheelset. While it shares derailleurs with RX620 12-speed, RX820 uses a lighter hollow alloy crankset and shifters. Further, the shifters themselves are most optimized for use with flared drop handlebars, and they use Shimano’s Servowave technology which improves the ability to more finely-control braking power.

Shimano GRX RX620 is also 12-speed, but it swaps levers for a simpler design. Further, the cranks are a solid forged alloy design that is heavier but equally capable. The brake calipers don’t receive the updated design, instead using the same brake calipers as GRX 10 speed.

Consumable components like brake rotors, cassettes, and chains are largely swappable across other 12-speed groups. GRX RX820 level groups tend to use Ultegra and Deore XT-level parts, while RX620 12-speed groupings tend to use 105 and SLX-level parts.

GRX 400 series components are largely for 10-speed drivetrains. Finishes and component materials are simplified to make them accessible to a wider range of riders. 10-speed GRX is only available with a 2x drivetrain.

Let’s talk Shimano WH-RX880 gravel wheelset

At the same time, Shimano has dropped a new wheelset charismatically dubbed the WH-RX880. It replaces Shimano’s GRX wheels as a wide-width carbon gravel wheelset.

RX880 wheels are one of Shimano’s first hubs to offer two different freehub options for Shimano’s road cassettes or their MTB cassettes alike with Microspline freehubs.

Quoted weights are 1394 to 1397 grams depending on freehub choice. The carbon rims offer a 25 mm inner width with a hooked bead and a 32 mm profile. Shimano says the rim is optimized for 32 mm to 50 mm tire clearances.

The RX880 hub uses a new Shimano straight pull hub. Like other top-end Shimano hubs, these still use a cup and cone bearing as opposed to a more common sealed hub bearing. And importantly, the new freehub designs aren’t currently interchangeable with other Shimano freehubs.

Component weights and prices

Shimano GRX isn’t necessarily a groupset with defined roles and components, which means the groupset you might find from a new bike won’t strictly adhere to one tier of component. That allows riders and bicycle manufacturers alike to mix and match components based on their needs. Listed below are the prices and weights of Shimano GRX 820-series and GRX 620-series components.