Shimano GRX 12spd Drivetrain [Rider Review]

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Gravel is here to stay. For those who gravel ride know that it's a growing sub-genre of mountain biking or maybe road riding? A lot of companies are releasing Gravel specific products that meet the demand for harsh all-road riding, but still being lightweight. See what our customer thinks of Shimano's GRX Drivetrain.

Overview

For the better part of two years, my Scott Scale hardtail has been working double time. Not just has it been my bike of choice for the XC races like the Lutsen 99er and Leadville 100, it’s also filling the role of my gravel bike. I’ve taken on gravel races and rides of 200+ miles with flat bars while surrounded by folks with drops (and been called crazy while doing so). While I do feel like I’ve been missing out on the aero and ergonomic benefits of drop bars the one thing that I’ve never questioned is my choice of the Shimano XTR drivetrain.

When I first rode Shimano’s 12 speed 1x drivetrain I immediately knew that I wanted the same wide range and shifting performance of Hyperglide+ technology with dropped handlebars. I considered the SRAM AXS “mullet” but as someone who rides off the beaten path, finds myself bike packing on weekends, and forgets to charge my phone, bike computer, etc. I knew I couldn’t rely on any electronics to keep my bike moving. I watched with envy as my friends equipped their mountain bikes with drop bars and their gravel bikes with wide range cassettes made possible by SRAM’s AXS technology yet I refused to go the way of electronic shifting and patiently waited for Shimano’s response. After waiting all year though the rumors and leaks the 12 speed gravel drivetrain was finally released and I immediately ordered a set of shifters and the matching rear derailleur for my mountain bike and I am happy to report that Shimano’s 12 speed GRX drivetrain was absolutely worth the wait!

Installation

Putting drop bars on my hardtail was actually pretty easy but I made things a little more complicated for myself to make swapping between the drop and flat bars easier in the future. I grabbed a flared drop bar and a shorter stem from my parts bin and ordered a pair of the new GRX brake levers/shifters and the new GRX rear derailleur from Worldwide Cyclery. The shift housing from the flat bar configuration wasn’t long enough for the drop bar shifter so I used an inline barrel adjuster to connect the existing shift housing to a short extension so I didn’t have to replace the whole shift housing though the frame. I used a similar brake like extension for the rear brake hose and 3D printed a cover that mimics the XT hose grommet and gives the existing grommet on the brake line a place to rest so it’s not bouncing around.

I used my existing XT M8100 brake caliper in the rear but decided to get a new brake caliper and hose for the front brake. This way when I swap the handle bars I can swap the front brake caliper out instead of bleeding it. The rear break will need bleed every time I swap the bars but I guess I’ll have to live with that. Lastly, the simple part, I installed the GRX 822 rear derailleur in place of the XTR rear derailleur. Paired with my existing Shimano 10-51 cassette and chain the conversion to drop bars was complete.

A brief review.

Simply put, GRX 820 brings the shifting performance you know and love from Shimano’s mountain bike line up to drop bars. The shifting is responsive, light, and brake lever/shifter has the excellent build quality we’ve come to expect from Shimano. Even under pedaling load the RX-RD822 rear derailleur quickly and cleanly shifts across the entire range of your choice of 10-45 or 10-51 12 speed cassette. The chain stabilizer, or clutch, shared with its mountain bike rear derailleur brothers, keeps things tight, and ensures chain retention when paired with a narrow wide chain ring. Just like the mountain bike rear derailleurs, a lever on the derailleur can disengage the clutch making shifting even quicker and cleaner on roads that don’t warrant the chain tensioner and makes removing the wheel a lot easier when working on the bike on and off the trail.

Brake performance is also excellent. My levers are paired to M8100 2 piston calipers so I can’t speak to the entire GRX system, only the levers. The GRX 820 brake levers utilize Shimano’s “servo-wave” technology and overall I’m very happy with the modulation and overall braking power.

Ergonomics are good. The levers seem identical to the previous generation of GRX RX-810 brake levers and very similar to the pair of Ultegra R-8020 calipers on my road bike.

Compatibility and upgrade path to 12 speed.

In my research and after my build I can address some questions you may have about the GRX system.

All 12-speed road levers are compatible with the GRX 822 rear derailleur. Currently there are three options. The 105 R7120, the GRX 610, and the GRX 820 series. Only the latter utilizing Shimano’s servo wave brake technology. There are short and long cage version of the GRX 822 rear derailleur for use with the 10-45 and 10-51 cassettes respectively. The road shifters use a different derailleur pull ratio than their mountain bike counterparts so there will be no mixing of mountain rear derailleurs with GRX shifters or visa-versa.

All cassette options from Shimano for the 1x GRX 820 drivetrain use the Micro Spline Freehub standard so if you’re looking to upgrade your existing drivetrain make sure that a Micro Spline Freehub is available for your wheelset.

Just like the mountain bike drivetrains shifting performance is the best when paired with a Shimano 12 speed chain. If you’re upgrading an existing gravel bike you can use the previous generation of GRX 810 cranks but will need to get a chainring that’s compatible with Shimano 12 speed chains. You can get one from Shimano or if you want an oval Wolftooth now makes round and oval GRX chainrings in their Drop-Stop-ST tooth profile that’s specifically designed for use with Shimano 12 speed chains. For folk converting their mountain bike to drop bars you can use any of the Shimano 12 speed mountain bike cranks from the Deore line though XTR or any crank that have a Shimano 12 speed compatible chain ring.

Final Thoughts

Overall, I am really pleased with this upgrade to my bike. I’ve added the ability to swap between drop and flat bars with relative ease without sacrificing any performance or gear range. One bike for any and every upcoming adventure. Looking to 2024 I’ve got my sights on drop bars at the Rule of Three and all bikepacking adventures and flat bars for more traditional mountain bike races like the Lutsen 99er and Chequamegon Fat Tire Festival.