Updated July 21, 2020
Shimano GRX is a component series designed for gravel and adventure riders, bikepackers and cyclocross racers, providing a wide spread of possible builds including 10-speed and 11-speed setups, 1x and 2x drivetrains, mechanical and electronic shifting, wide-range or close-range gears, and dropper post integration.
Shimano hasn’t exactly developed an entirely new groupset. Instead, it has combined key technologies and components from current road and mountain bike road groupsets and added some brand new parts. Even so, Shimano calls GRX the “world’s first dedicated gravel component group".
GRX is divided into three different levels:
• RX800 Shimano Ultegra level and 11-speed. You can get mechanical and electronic (Di2) setups.
• RX600 Shimano 105 level and mainly 11-speed (although there is a 10-speed RX600 chainset too). Shifting is mechanical only.
• RX400 Shimano Tiagra level and 10-speed. Shifting is mechanical only.
That's all simple enough, but things are complicated by the fact that you can't get every component at every level. You can't have a complete RX600 groupset because there's no such thing as an RX600 rear derailleur, for instance; if you want an 11-speed mechanical rear derailleur you need to go for RX800 level. In other words, you sometimes have to mix and match.
For this reason, it's easiest to decide first whether you want:
• 11-speed Di2
• 11-speed mechanical
• 10-speed mechanical
You can then look at the options available within each category. This is the way that Shimano structures everything on its website.
Not surprising given GRX's intended use, you get hydraulic disc brakes across the board.
Cassette and chain options come from current road (Ultegra, 105, Tiagra) and mountain bike (XT, SLX, Deore) groupsets.
Let’s look at GRX in detail, broken down into each component type.
There are three types of chainset to choose from: 1x11-speed, 2x11-speed, and 2x10-speed (there is no dedicated 1x10-speed chainset). Each has a chainline that has been shifted outwards by 2.5mm compared with existing road components for increased tyre and frame clearance.
The GRX 800 series chainset is available 2x with 48/31-tooth chainrings, and 1x with either a 42-tooth or 40-tooth chainring.
The GRX 600 series chainset is available 2x with 46/30-tooth chainrings, and 1x with a 40-tooth chainring.
There is no GRX 400 series chainset. Instead, there's a RX600 10-speed chainset with 46/30-tooth chainrings.
The key difference between the GRX 800 chainsets and the GRX 600 chainsets is that GRX 800 uses Shimano's Hollowtech II hollow crank arm technology to reduce the weight.
The single ring chainsets use Shimano’s Dynamic Chain Engagement tooth profile – tall teeth that are alternately thick and thin, specially shaped to prevent the chain bouncing off on rough terrain.
road.cc reviewer Mike Stead tested the GRX RX810 chainset (pictured above) with a 40-tooth chainring and said, "The combination of the [rear derailleur] clutch (see below) and alternating chainring tooth profile meant no matter what I tried, the chain stayed put and was almost totally silent."
You can have a GRX groupset with either a mechanical or electronic front derailleur.
Compared to regular road front derailleurs, the GRX front derailleurs have an additional 2.5mm outboard clearance to provide space for wider tyres, up to 42mm.
For this reason the front mech must be used with the matching GRX chainset (see above) which is similarly pushed outward from the frame by 2.5mm.
Both the RX810 mechanical front derailleur and the RX815 Di2 front derailleur (pictured above) have the capacity to accommodate a 17-tooth difference between chainring sizes (as found on a 48/31-tooth GRX chainset) while the RX400 10-speed front derailleur accommodates the 16-tooth difference between the RX600 chainset's 46/30-tooth chainrings.
Dave Arthur used the RX810-F front derailleur and said, "Front shifts [were performed] well despite that 17-tooth jump between the two rings and being asked to do so in adverse conditions and with a regularity that rolling terrain requires."
Mechanical and electronic GRX rear derailleurs are available. All of them use Shimano's Shadow RD+ technology which is designed to stabilise the chain on rough terrain by minimising unnecessary derailleur arm movement. The idea is that this provides more secure chain retention, reduces the amount that the chain slaps on the chainstays, ensures a quieter ride, and results in an uninterrupted shifting performance.
Each rear derailleur has a stabiliser on/off switch that allows you to change the chain tension and minimise bounce.
The GRX derailleurs sit further underneath the cassette than traditional road derailleurs – they don't extend so far out when you're using the small sprockets. The idea is that this makes the derailleur less exposed and vulnerable to damage by things like undergrowth and rocks.
road.cc's Dave Arthur rode both mechanical and Di2 versions of GRX in atrocious conditions and said, "[The groupsets] kept changing gear with the usual metronomic precision that Shimano groupsets are known for. I suffered no mis-shifts at all, no grinding gears, no evidence that it couldn’t cope with grimy riding.
"The mechanical groupset worked beautifully [and] GRX Di2 is a clean shifting groupset that proved unflappable over three days of riding. I regularly asked the groupset to change gear in extreme circumstances, deliberately shifting under load and cross-chaining, but nothing I did invoked any reluctance.
"The proven clutch-style rear derailleur and Shimano’s patented chainring tooth design ensured the chain stayed in place over the roughest tracks. No chains were dropped. No noise from the chain slapping the chainstay."
If you're using a Shimano Ultegra or 105-level 11-30/34-tooth 11-speed cassette, you need to use the short cage Di2 RD-RX815 rear derailleur or a mechanical RD-RX810 rear derailleur (pictured above). If you're using a 10-speed system, you need the RD-RX400 which can cope with a maximum 36-tooth sprocket. It uses more steel and less aluminium than the RX800-level rear derailleurs, hence a higher weight.
Riders choosing an XT, SLX or Deore-level 11-40/42 cassette need to use the longer cage Di2 RD-RX817 (pictured above) or mechanical RD-RX812, both of which come with a pull ratio similar to Shimano’s road derailleurs.
Shimano offers dedicated GRX STI (combined shift and brake) levers, mechanical and electronic, which use what the brand calls a “gravel-specific ergonomic” lever design.
The hood shape is taller than normal to provide a more secure hand position on rough ground. The idea is that you can butt your hand up against the front end of the hood to stop it sliding over the top. There's a deeper scoop in the centre of the brake lever too, along with an anti-slip textured finish to provide a better grip.
Dave Arthur said, "The most successful aspect of the new groupset is the new hoods. Put your hands on the hoods and, provided you’re familiar with Shimano’s current groupsets, you’ll notice they’re quite different. The result is much-improved control, comfort and braking when riding down steep descents or slithering down a muddy path.
"Shimano has spent a lot of time studying the demands of riding a drop bar bike off-road on challenging terrain. A key change is the higher braking pivot which makes braking on the hoods easier. The lever has also been reshaped and is wider, and there are textured ribs on the hoods for more grip in slippery weather.
"The change is more pronounced on the Di2 shifters. Because the electronic gubbins takes up less space compared to the mechanical components, Shimano has had more freedom to produce a hood shape that feels fantastic in the hand. The top part of the hood curves back, letting you hook your hand into the hood for a more secure grip. It leads to an enhanced sense of control.
"Another reason the braking is improved on the ST-RX815 Di2 levers (above) is the addition of the company’s Servo Wave technology from its mountain bike brakes. This alters the lever feel with more progression. The first part of the lever travel is very light and the brakes respond instantly, with the progression leading to easier modulation of braking power as the terrain gets rowdier."
Shimano says that the level of stopping power provided by the non-Servo Wave RX810 (pictured below), RX600 and RX400 levers is akin to Ultegra, 105 and Tiagra disc brakes respectively.
Shimano offers a mechanical shift ST-RX810-LA left lever that, when used with a 1x11 drivetrain, can control a dropper seatpost. The integrated cable-pulling system is compatible with cable-operated dropper posts with a 9mm lever throw.
Shimano GRX also includes 1x11-specific BL-RX810 and BL-RX600-series left side hydraulic disc brake levers with no dropper or shift internals.
If you wanted a 1x system with RX600-level components, for example, you'd buy an ST-RX600-R right shifter and a BL-RX600-L left brake lever.
The inline hydraulic sub-brake lever (BL-RX812, pictured above) is an interesting option. It attaches to the top section of your handlebar and connects to the main hydraulic line running to the front and/or the rear caliper to give you a second braking position.
We can certainly see many situations when this would be useful – cyclocross and the cobbled classics, for instance. If you use the Di2 system and fit satellite shifters, you'll be able to change gear with your hands on the tops too.
|ST-RX810-LA (dropper post lever)||263g||£179.99||£151.00|
|BL-RX810-L (L-side only)||222g||£179.99||£137.00|
|BL-RX600-L (L-side only)||227g||£159.99||£121.00|
You can also buy STI levers and brake calipers in sets. See below for details on those.
The flat mount brake calipers (BR-RX810 pictured) are the same design as the current road calipers – but with GRX logos – so they come with features like one-way bleeding and Shimano's Ice Technologies heat-dissipating finned brake pads and rotors. This helps keep them cool, maintaining the braking performance.
Dave Arthur said, "The brakes coped with demanding high-speed descents and awkward low-speed tight downhills. The flat mount calipers and rotors are carried over from Ultegra with the same caliper design and rotor sizes, and as such the braking performance was familiar, powerful and consistent."
|Model||Weight (f/r)||RRP (f/r)||Typical price|
As well as buying the GRX STI levers and brake calipers separately (details above), you can buy them as sets (ST-RX810/BR-RX810 pictured above).
|Model (lever/caliper)||10/11-spd||Di2/mechanical||Weight||RRP||Typical price|
Two sets of tubeless-ready wheels round out the GRX range: a 700C option (pictured) and a 650B option. Each has a rim with a 21.6mm internal width and 22mm depth, and the hubs are 12mm thru-axle.
|Model||Weight (f/r)||RRP (f/r)||Typical price|
We’re impressed by what Shimano has delivered. It was a long time coming but Shimano now has a well-considered range of options that should keep most gravel and adventure riders happy.
Dave Arthur said, "It’s just a shame Shimano wasn’t a little braver in offering a game-changing groupset to serve as a serious riposte to its rivals and offer the low and wide-range gearing that many people flocking to gravel bikes want."
That said, GRX is still very good equipment and the range will suit the majority of those speccing their own gravel/ adventure bikes, as well as giving bike brands plenty of options when it comes to building new models.
GRX provides sensible gearing for Shimano-equipped bikes – so hopefully no more roadie compact (50/34-tooth) chainsets on gravel and adventure bikes. The decision to offer three ranges covering both 10-speed and 11-speed ensures it is an accessible proposition too.
"Overall, the experience is one of trust," said Mike Stead, talking about using GRX 600 in particular, "It shifts with typical Shimano 105-or-better accuracy, and the chain won't fall off unless you do something spectacular. Your hands stay put on the hoods, and your fingers are able to brake and shift even when cold, wet and muddy. When something wears out you'll have a load of options for replacement. If your needs change, it's likely you'll find a compatible alternative for a component at a decent price."
"It's affordable, easily upgradeable, works with many other Shimano components, and most of all works out on the road or trail to deliver a flawless shifting and braking experience in the worst of weather or trail conditions."
"No doubt we'll see wider-range rear mechs and 1x chainrings appear, further broadening the scope of terrain and luggage you can tackle without upgrading an entire groupset. It's this typically Shimano system-thinking that makes GRX a good investment."
Get more info from Shimano's website.
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Mat has been in cycling media since 1996, on titles including BikeRadar, Total Bike, Total Mountain Bike, What Mountain Bike and Mountain Biking UK, and he has been editor of 220 Triathlon and Cycling Plus. Mat has been road.cc technical editor for over a decade, testing bikes, fettling the latest kit, and trying out the most up-to-the-minute clothing. We send him off around the world to get all the news from launches and shows too. He has won his category in Ironman UK 70.3 and finished on the podium in both marathons he has run. Mat is a Cambridge graduate who did a post-grad in magazine journalism, and he is a winner of the Cycling Media Award for Specialist Online Writer. Now pushing 50, he's riding road and gravel bikes most days for fun and fitness rather than training for competitions.