Shimano is going all-in on gravel, launching a full line of GRX drivetrains with a wide range of interesting options for the off-road crowd.
The new GRX line covers Di2 plus three levels of mechanical shifting, plus 1x and 2x drivetrain options. There’s also a new, wider GRX wheelset to work better with higher-volume tires. Along with all the expected drivetrain parts, all redesigned for the demands of gravel road, there’s a few innovative new features. A drop-bar dropper post option for 1x drivetrains, and the first inline hydraulic brake levers will surely attract the attention of the gravel crowd.
GRX: Three tiers, many options
Shimano’s jumping into gravel with both feet. Instead of releasing a top level drivetrain and following up with more budget friendly options, three levels of GRX arrive at the same time.
The top end is, following Shimano’s numbered series naming convention, RX810. The 11-speed drivetrain can be run as a 1x or 2x system. This top level is further split between Di2 and mechanical series, which share components such as cranks and brake calipers.
Next is RX600, which is also available as 1×11 or 2×11. RX600 is a mechanical only series. Last, there is the 2×10 speed, mechanical RX400 drivetrain. All three series use hydraulic disc brakes.
GRX rear derailleur: five options cover all bases
To hit the balance between efficiency and reliability required for mix-terrain riding, all GRX rear derailleurs use Shimano’s Shadow RD+ Stabilization. Turn the stabilization on when you’re off road for added security, then disengage when you return to tarmac.
To cover the diverse gearing ranges being demanded by gravel riders, 11-speed GRX rear derailleurs come in a long- or short-cage version. The short cage derailleurs cover a cassette range from 11-30 to 11-34. The long-cage versions cover from 11-40 to 11-42 cassettes. A single mechanical RX400 series rear derailleur covers 1×10 cassettes in a range from 11-32 to 11-36.
Shimano’s GRX rear derailleurs are compatible with existing Di2 / mechanical Dual Control levers. In a second nod to simplicity and cross-compatibility, all Shimano GRX drivetrains use existing chains and cassettes from Shimano’s road and mountain line-up.
Levers and hoods redesigned for off-road demands
For the top-tier Di2 lever, Shimano has relocated the braking axis to provide more leverage, compared to the existing 9170 Di2/Hydro road levers. The new position is supposed to make it more comfortable to brake from the hoods. The mechanical GRX lines use the same shift/brake body as existing hydro lever road options.
All GRX shifters/levers, get an updated lever blade, which has been curves slightly to make it more comfortable to access from a wider variety of hand positions. The lever blade and hood have been textured to provide more grip over rough terrain, including a surface coating on the lever blades borrowed from the fishing side of Shimano that provides more grip in the wet.
GRX series cranks and chainrings
Two new RX series cranks will be offered. The RX810 series cranks and the RX600. Both cranks shift the chainline outboard by 2.5 mm. This improves frame and tire clearance for larger volume tires. It also means GRX cranks can only be used with GRX front derailleurs.
RX810 series cranks will come in 40 or 42-tooth chainring options for 1x drivetrains. For the 2x system, Shimano pushed a big 17-tooth jump between chainrings, its widest ever, for a 48-31 gearing. GRX 800 series cranks are available in 170, 172.5 and 175 mm options.
RX600 gets more length options, adding a 165 mm length, and different gearing. The 1×11 crank only comes in a 40-tooth ring, and 2x comes with 46-30 chainrings.
RX400 series uses the same RX600 series crank, but with 10-speed specific chainrings.
Front derailleurs: double chainrings and gravel specific chainline
Three GRX front derailleurs will be offered. 2×11 gets a mechanical and Di2 option, plus a 2×10 version. To accommodate the larger-volume tires that have become popular in gravel riding, Shimano has moved the chainline out 2.5 mm for its gravel groupset. This means that GRX cranks must be used with GRX front derailleurs.
Inline brake option and dropper post lever compatibility
For 1x mechanical systems, Shimano has even more options. In place of the standard lever, you can get a 1x specific left lever that is just a dedicated brake lever. There’s no shifting internals on the dedicated brake lever, but Shimano has built in some side-to-side play to keep the lever safe in a crash.
If you’d rather get rad than get light, both the GRX 600 and 810 1×11 series offer the option to run a left lever that functions as a dropper post lever instead of a shifter. This drop bar dropper post lever will work with internally and externally routed posts, so long as the cable head attaches at the lever end, not the post end. There’s no dropper post lever option for Di2 or 2×10 speed GRX. The dropper lever will be sold as a stand alone component, so you can switch between the different options. Or, if you’re not concerned about having matching levers and really want a dropper and Di2, mis-match it with a right side electronic lever on a 1x, drivetrain, though Shimano may object purely on stylistic grounds.
All GRX drivetrains will have the option to run an inline brake lever for the hydraulic disc brakes. This adds control in more hand positions while riding, since you can brake while riding on the tops instead of having to reach for the hoods or drops. Use that freedom to change up your hand position for comfort on long rides, or drop your seat and throw sick whips while on the tops, it’s up to you.
GRX wheels get wide to go off road.
Shimano has generally been on the conservative side when it comes to the internal width of their rims, until now. The GRX gravel wheelset goes all in off road. All rims are a 21.6 mm internal width and tubeless compatible. You also have the option to run 700c or 650b wheels. The GRX wheelset is 100 x 12 mm up front, and 142 x 12 mm in the back. The gravel road wheelset retails for US $420, possibly in a nod to the more relaxed attitudes of the gravel road crowd.
Shimano GRX Di2
Shimano 11-speed mechanical GRX
Shimano's 2x10 gravel option
Not all of Shimano’s GRX range will drop at the same time. Mechanical 1×11 and 2×11 systems arrive first, with expected delivery being in July. GRX Di2 1×11 and 2×11 arrives in August. The dropper post lever and sub-levers are expected in September.