Acknowledging the rapid rise of gravel and adventure riding, Shimano has unveiled not just one groupset but a whole new component family.
Coming under the new GRX moniker, the components have all been designed and built to cope with fast riding over loose terrain. Taking over from the older, cyclocross specific CX groupsets, Shimano has tuned all aspects of GRX to suit a wider audience and with it has provided a perfect way of mixing and matching components to suit individual rider needs, including full compatibility with existing road and mountain bike groupset parts.
The GRX cranksets are built for tackling different riding terrains and riding styles, all coming with a +2.5mm chainline for increased tire and frame clearance.
GRX single ring cranksets offer the simplicity of shifting only on the rear cassette (options include RX800/600 40T cassettes or the RX800 42T cassette) and are delivered with Shimano’s Dynamic Chain Engagement tooth profile on the front chainring to offer increased chain retention over bumpy ground. Meanwhile the GRX double chainring RX810 crankset employs a 17-tooth gap which, at 48-31T, is the company’s widest-ever gear ratio.
Together with the additional RX600-11/10 46-30T options, the double cranksets give big enough gear ratios for tackling the steepest climbs and pinning the steepest descents.
The Di2 (FD-RX815) or Mechanical (FD-RX810/RX400) front derailleurs are built with 2.5mm more outbound clearance for wider tires (up to 42mm) to cope with riding on rough roads. This means GRX front derailleurs must be combined with Shimano GRX +2.5mm cranksets. Both RX800-series mechanical and Di2 front derailleurs are built to accommodate Shimano’s widest 17T front chainring 48-31T gear ratio whilst the FD-RX400 10-speed derailleur accommodates the 16T chainrings found on the RX600 46-30T 10-speed cranksets. Shimano Di2 FD’s can be adjusted using Shimano’s simple and integrated controls whilst mechanical FD’s should the light front shifting feeling that Shimano is well known for as well as toggle link construction for more cable routing options and an integrated cable tension bolt for precise and easy adjustments.
Adopting the technology introduced in 2018’s RX rear derailleur, the GRX Di2 RDs (RD-RX815/RX817) or mechanical RDs (RD-RX810/RX812/RX600) are designed for silent, smooth and reliable shifting on rough terrain with a chain stabilizing system known as SHADOW RD+ to manage ‘chain chatter’, minimize unnecessary derailleur arm movement and provide uninterrupted shifting performance.
GRX comes with the choice of four derailleurs depending on which cassette and gear shifting operation you choose. Riders using an Ultegra, 105 or Tiagra level 11-30/34T cassette will need to use the short cage Di2 RD-RX815 or mechanical RD-RX810 rear derailleur, whilst riders choosing a Deore XT, SLX or Deore level 11-40/42 cassette will need to use the longer cage Di2 RD-RX817 or mechanical RD-RX812 RD, both of which come with a pull ratio similar to Shimano’s road derailleurs.
GRX shifting comes courtesy of dedicated gravel-specific ergonomic levers (Di2: ST-RX815 or Mechanical: ST-RX810/RX600/RX400, ST-RX810-LA) featuring an 18mm higher axis point, curved brake lever profile and anti-slip textured finish.
To integrate the use of dropper posts in gravel riding, Shimano created the GRX mechanical ST-RX810-LA left hydraulic disc brake lever that, when used with a 1x11 drivetrain, can control a dropper post whilst also keeping the cockpit tidy. The integrated cable pulling system has a 9mm lever throw to operate dropper posts with cable heads at the shift lever.
Shimano GRX also includes 1x11-specific RX800 and RX600-series left side hydraulic disc brake levers with no dropper or shift internals, including the 1x11 Di2 left-hand lever (ST-RX15), which comes with three buttons (two side buttons and a hood top button) for operating ancillary functions such as lights or 3rd party cycling computers.
GRX STI shift/brake lever weights: ST-RX815-L/R Di2: 565g, ST-RX810-LA Left side dropper post lever: TBDg, ST-RX600-L/R: 611g, ST-RX400-L/R (10-speed): 613g
Shimano GRX Braking systems
A primary concern of gravel riders is having enough brake power to control speed on steep and sudden descents. At the top tier of the GRX family, one variant of the RX800-series brake levers (ST-RX815) offer Shimano's mountain bike Servo Wave technology. This provides a stronger braking feeling with greater modulation options for more aggressive riding. If you prefer the RX810 non-Servo Wave version, or the RX600 and RX400-series levers, The Shimano says these will still provide an excellent level of disc brake stopping power, akin to Shimano Ultegra, 105 or Tiagra road disc brakes.
An additional braking option comes with an inline hydraulic sub-brake lever (BL-RX812-L/R) which connects to the main hydraulic line running to the front and/or the rear caliper. The sub-brake lever is designed to be mounted on the handlebar next to the stem offering options for braking when riding with hands on the tops.
The GRX calipers (BR-RX810/400) echo the design of Shimano’s flatmount road calipers, taking features like one-way bleeding and Ice Technologies' heat-dissipating finned brake pads and rotors.
Gravel-specific Wheelset
Shimano is offering with two gravel/adventure-inspired 12mm E-THRU axle wheel sets in the GRX range (WH-RX570-TL-F12/R12). The 700c or 650b (non-Boost) tubeless-ready wheelsets should offer, according to Shimano, an optimal balance between weight, stiffness and gravel durability, bringing a wider 21.6mm inner rim width (comparable with MTB XC wheels) and an off-set rim height of 22mm.
James Bracey's career has seen him move from geography teacher, to MBR writer, to Cycling Weekly's senior tech writer and video presenter. He possesses an in-depth knowledge of bicycle mechanics, as well as bike fit and coaching qualifications. Bracey enjoys all manner of cycling, from road to gravel and mountain biking.
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