What is Shimano GRX? Is it Better for Gravel?
Shimano’s new GRX drivetrain brings more options more riders
WHAT’S GOOD FOR GRAVEL IS GOOD FOR ALL
For the last few years many have chided Shimano for not playing a stronger hand in the gravel market. When they unveiled the Ultegra RX derailleur last year, along with a pretty soft-core gravel shoe, the gravel geeks (like us) just shrugged and asked, “Is that all you have to show?!” Isn’t that just like the bike industry?
And then when the component giant announced that they were rolling out a gravel-specific drivetrain, just as many people were shocked. Sure, we all recognized the meteoric growth of gravel, but was a dedicated drivetrain line really necessary? Could it be a thing? And if it did, what would it look like and offer, and what about it would make it gravel-specific?
Funny thing, but after getting time aboard Shimano’s 1x, 2x, mechanical and electronic versions of their new GRX drivetrain, it’s clear that this gravel-specific group could benefit the road purist just as much as the gravel explorers, as well as everyone in between.
WHAT IS GRX?
While Shimano touts the GRX as the world’s first gravel-specific component group, following both a deeper dive at a Shimano ride camp, along with many hours logged on our home trails, we came away with it as a line of components that further expands the drop-bar category in multiple directions. Sure, it was a ground-up design, but almost all of the components are compatible with existing gruppos. Instead of expanding their already-expansive road designations, the GRX insignia helps navigate what is now a vast offering of shifters, derailleurs, cranks and other small parts with the potential to commingle.
GRX is also the first non-mountain bike 1x drivetrain from Shimano. Though late to officially jump into the G-world, in typical Shimano fashion, the GRX parts were years in the R&D process, beginning with last year’s soft launch of the Ultegra RX rear derailleur acting only to whet our appetite of what was to come.
In actuality, the GRX line further expands the capabilities of Shimano’s road offerings while also minimizing the need to recruit from the mountain side. In the past, only Di2 was capable of utilizing the mountain bike derailleurs because of the difference in cable-pull ratio on the mechanical systems.
WHY IT’S BETTER FOR EVERYONE
With the addition of the GRX line, Shimano is no longer watering down the road gruppos to work off-road. Shimano realized that the hard-core road rider feared that their Dura-Ace and Ultegra drivetrains were being co-opted to accommodate circumstances that didn’t apply to their needs.
Now with the GRX line Shimano has made a clear distinction between technology intended for paved and unpaved roads. Better yet, it’s all inner compatible, so you can mix and match. The only exception is the new GRX front derailleur and 2x cranks have to be paired, meaning you can’t use an Ultegra crank with a GRX front derailleur or vice versa.
For the adventure rider, you can now have a mechanical shift system that offers a wide spread of gears without a widget that changes the pull ratio of your road shifter to a mountain derailleur. At the end of the day, the drop-bar market is expanding, and that can only be considered a good thing for all of cycling.
For people who thought their only wide-ratio option available was buying a mountain bike, even though they never intended to hit a trailhead, they now have drivetrain components designed with them in mind. Those long dirt roads that connect the east and west are more of an option than ever before, and GRX looks to fill the void.
THE MECHANICAL ADVANTAGE
GRX is offered in a few tiers on the mechanical side of things, starting with an entry-level, 400-series
10-speed group that offers many of the same advantages of its 11-speed counterpart but at a more affordable price point. Moving into 11-speed, there is the 600 series that offers a 1x 40t or 2x 46/30t crankset, as well as its
own dedicated levers that can be used on either 1x or 2x systems.
Finishing out the mechanical offerings are the 11-speed 800 series, which includes 2x and 1x levers, with the latter including a matching left lever that is a brake only. If your adventures might require a dropper post and you are using 1x, then there is a left lever that is designed specifically to actuate compatible posts.
There is a new GRX 800 series front derailleur that has a chain line that has been bumped out 2.5mm to make room for bigger tires. The wider chain line means it is also designed specifically for the GRX cranks.
The bigger differences are found with the rear derailleurs. There are two options—the 2x RX810 that is designed to accommodate cassettes between 11t to 34t and the 1x RX812 derailleur, which has a shorter cage length to fit either the 11-42 or 11-40 cassettes. This is big news, because as we mentioned above, this is the first 1x offering for drop bars from Shimano, as well as the first mechanical derailleur capable of accommodating those cassette sizes.
Both use an adjustable chain stabilizer to minimize chain slap, and there is a clutch switch used to turn the system off. Although the stabilizer and clutch systems were adopted from the mountain side, it uses its own GRX-specific tension. During Shimano’s extensive testing, they found that the specific demands—from bike styles and terrains—that gravel puts on the drivetrain required its own base-system tension.
Of course, no Shimano group of this magnitude would be complete without a Di2 option, and that would be found with the 800-series system. As with the mechanical versions, there are both 1x and 2x battery-operated derailleurs. However, when it comes to the hand controls, there are some big changes in design and ergonomics. Shimano used their Gravel Alliance test group as R&D partners, and one of their biggest points of feedback concerned the Di2 controls.
While the current road levers are small, sleek and pair well for pavement duties, on the rough-and-tumble gravel roads, Alliance riders didn’t feel they offered the ergonomic security needed, thus a new hood design that almost hooks your hand like an old-school mountain bike bar end. The top Di2 button that many use to control their computer screens or as additional shifters has been moved to the inside of the lever. This means you can almost pinch the button rather than having to release your grip to reach the top mount location.
THE ERGONOMIC CONTROLS
At first glance, the mechanical shifters don’t look all that different from their Ultegra cousins, and you would be correct. On the mechanical side of things, the body and function of the levers are nearly identical, but the hoods now have ridges that offer better grip, especially when wearing gloves. But the biggest difference is the lever blade, which is now more appropriately referred to as a paddle owing to its wide profile. The lever also has a new textured surface (borrowed from Shimano’s own fishing department) that now provides an improved level of security, especially over rough terrain. The levers have also been angled out a bit more from the perch than the Ultegra levers.
“For people who thought their only wide-ratio option available was buying a mountain bike, even though they never intended to hit a trailhead, they now have drivetrain components designed with them in mind.”
For the Di2 versions the changes have gone deeper. The new design has also moved the pivot point of the brake lever 18mm higher to provide increased leverage. This new pivot point seems to help in modulation and power. Like the mechanical versions, the Di2 controls also get the new hoods and wide, textured levers.
Definitely rating as all new are what Shimano is calling the two sub levers that sit inboard on the flats of the handlebars. While we’ve seen cable-pull versions of these for years, these micro-sized hydraulic levers are run inline and provide an added braking position.
For the 800 series, there is a 2x crank with a 48/31t, which, at a 17t delta, is the widest that Shimano has ever offered. The 800-series 1x crank is offered in 40 or 42 teeth, and both the 2x and 1x cranks utilize the same spider and arm so they can be interchanged. The 800-series cranks are almost 100 grams lighter, thanks to their use of Hollowtech II technology. The GRX cranks like the front derailleur sit 2.5mm wider at the rings. They utilize the same bottom brackets and spacing at the spindle, but do widen the Q-factor to 151mm.
The GRX brake calipers come in the 800 series and the 400 series. Both offer a front- and rear-specific design, meaning there are a total of four calipers. The main difference seems to be the finish color since they weigh and are priced the same. If you happen to have invested in a frameset that uses the older post-mount design instead of the now more popular flat-mount style, you can use the Shimano RS785 caliper with all the new GRX controls.
As with the Ultegra and Dura-Ace Di2, GRX also uses Shimano’s three-mode (full, semi, manual) Synchro shift, which automatically shifts either the front or rear derailleur to eliminate cross chaining.
We tested the GRX Di2 system in all the settings, and they all worked perfectly. We will say that if you are not ready for the front to shift on its own (full synchro), it can be a bit startling, as the front and rear simultaneously change. One thing that helped is we paired the Di2 system to our Garmin head unit, which when in full synchro will notify you that your next shift in that same direction will change the front position as well as the rear. The Garmin can also display a few other Di2-specific things, but that seemed to be the most useful, as well as the battery level.
THE GEARS AND SMALL BITS
Let the bike shops rejoice, as Shimano has not added to their already-extensive line of cassettes and chains. The GRX gruppo uses the existing road and mountain cassettes. Things to remember are that Shimano does offer cassettes that are outside the parameters of the GRX compatibility, so check with your specific setup.
As a guideline, never exceed the low sprocket max (easy gear), and make sure to calculate that you don’t exceed the rear-derailleur total capacity. The rear-derailleur total capacity is calculated by taking the difference between the front chainrings (48 - 31 = 17) and the difference in the cassette (34 - 11 = 23), then add them together (17 + 23 = 40). Forty is the max for the longer 2x derailleur and 31 is the max for the shorter 1x version (calculated by the difference in just the rear cogs). Got that?
Overall, the cross-compatibility here is one of our favorite features since it seems that every new item lately needs its own new set of tools and small parts.
THE 1X RIDE
When we first were browsing over the GRX 1x offering, we were slightly disappointed. It didn’t seem to address some of our issues like the lack of a 10t rear cog, and it didn’t seem to add anything that we couldn’t do with a mountain derailleur. But we were not looking hard enough, and what it added was the capability to run 1x on a much more realistic budget. In the past it was Di2 or nothing since the pull ratio was different, and let’s be honest, Di2 can be a budget-buster for many of us.
Our 1x mechanical drivetrain is simple and offers our golden requirement of a 1:1 ratio on the easy side. Shifts are crisp and spot-on all the way through the 11-40 cassette. Gear gaps are big on a cassette like this and can make it hard to match your preferred cadence to the speed of a group. This can leave you spinning too fast or too slow to hold the pace. This was not a problem on the unpaved roads.
“We love the simplicity of a 1x system, but it’s hard to beat the tight gears and wide range of
For us, the biggest drawback to the 1x system is the tall sprocket being limited to an 11t cog. For many this might not be a problem, but here in SoCal we have a lot of extended descents that exceed the max gear of our 40×11 and even a 42×11. As an example, with the 40×11 at 100 cadence, the top speed is about 30 mph, while the 42×11 is only a nominal 2-mph faster.
On our 1x test bike we have the left lever that only functions as a brake lever. The overall feeling of the new brake-lever blade is secure and solid. One finger is all we needed for slowing in most situations. The new hood ridges were nice with gloves, but when barehanded, they caused some discomfort when we didn’t change positions for a while. The new brake-lever texture seems to offer a bit more finger traction when your hands are wet as well, but not so much that it’s abrasive.
THAT 2X EXPERIENCE
We didn’t get as much time on the 2x system as we did on the 1x, but we definitely felt that the GRX gruppo shined brighter with a front derailleur. Sure, our 2x is also using the new Di2 800-series components, but what actually stood out was the gear range with minimal gaps. One reason that the 1x has made a huge impression is because bikes had a hard time fitting the front mech around the larger gravel tires. With the 2.5mm offset, this is now less of an issue. The tighter 11-34 cassette on our test bike offered much tighter gears, making group rides, solo rides and even singletrack fun with the correct gear just a shift away.
The 48/31 crankset offers a lower ratio than our relished 1:1 ratio and easier than our 1x, but with a much larger top gear. It’s even larger than you would get on a 1x system that uses a 10t cog. Since Shimano seems to be the front mech masters, we weren’t surprised that even with a huge 17t delta the chain never skipped a beat on front shifts. As we’ve always come to expect from Shimano, the Di2 worked without any problems. The electronic system still won’t let you cross-chain in the small ring and the small cog, but it’s rare that we find ourselves there with the delta gap so big.
The new ergonomics of the Di2 controls are exceptional. The new shape makes for long periods in the same position comfortable, but same as the mechanical, the ridges on the hoods are best for those who wear gloves. Also, the same as the mechanical versions the brake-blade texture and shaping only add to the experience.
Thanks to the new pivot position, the added leverage helped with modulation; however, since Shimano’s disc brakes have always worked so well, it was hard for some to tell any difference. The Di2 shift buttons are large, and in addition to a difference in texture, one button is concave while the other is convex.
Overall, the new Shimano GRX family of components looks to expand the drop-bar market for even more styles of riding. Of course, for both rider preference and cost considerations, the ability to choose 1x or 2x on either mechanical or Di2 is a huge benefit.
While there are some details that we think could be improved, what GRX brings to the market supersedes any faults. We love the simplicity of a 1x system, but it’s hard to beat the tight gears and wide range of the 2x. At the end of the day, the GRX line offers more options for more riding styles without taking anything away from existing systems. Mix and match is the name of the game, and Shimano now offers the most expansive drop-bar component lineup.
Photos: Kevin Fickling/Shimano