On June 26th 2018, Shimano Inc filed for the GRX trademark name, and people have been guessing what this mysterious GRX name will encompass.
Today we can happily tell you to stop wondering, because after nearly a year we can finally spill the beans. The Shimano GRX is a world first dedicated gravel/adventure component series.
Following extensive market research as well as many hours of talking to riders from all sorts of backgrounds from different parts of the globe, Shimano believes the world is ready for a fast riding loose surface dedicated groupset. Developing the series took the company’s development team well outside traditional confines to create a platform that addresses riders’ needs, be it for gravel riding, modern adventures, road cycling, bikepacking or fulfilling the demands of cyclocross racing.
The GRX series offers 1x11, 2x11, and 2x10 speed drivetrains in either a mechanical or Di2 electronic shifting option, which Shimano say will allow riders to tailor their own riding experience based on what type of terrain they usually encounter. These will be partnered with front and rear derailleurs, disc brake callipers with an in-line brake lever option, as well as left and right STI hydraulic levers, in either Di2 or mechanical shifting option, surely there is something for everyone.
The GRX cranksets are built for tackling different riding terrains and come 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. GRX crankset weights:
1x11: FC-RX810-1: 655g, FC-RX600-1: 753g.
2x11: FC-RX810-2: 722g, FC-RX600-11: 816g, FC-RX600-10: 819g
GRX Front derailleurs (FD)
Complementing the cranksets, 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. GRX front derailleur weights:
FD-RX815-F: 131g, FD-RX810-F: 94g, FD-RX400: 95g
GRX Rear derailleurs (RD)
Adopting the technology introduced in 2018’s RX rear derailleur, the GRX Di2 RDs (RD-RX815/RX817) or mechanical RDs (RD-RX810/RX812) 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 rear derailleur weights:
Di2: RD-RX815/RD-RX817 288/322g.
Mechanical: RD-RX810/RD-RX812 251/264g.
GRX STI levers
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 which can be gripped with assurance over rough terrain.
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 computers.
GRX Braking systems
A primary concern of gravel riders is having enough brake power to control speed on steep and sudden descents. That’s why, at the top tier of the GRX family, one variant of the RX800-series brake levers (ST-RX815) offers Servo Wave technology coming from Shimano’s mountain bike brakes. 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, they still provide an excellent level of disc brake stopping power, akin to Ultegra, 105 or Tiagra road disc brakes respectively.
An additional braking option comes with the 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) echoes the design of Shimano’s flat mount road calipers to deliver powerful brake performance, with features like one-way bleeding and ICE TECHNOLOGIES heat-dissipating finned brake pads and rotors to offer efficient cooling and long-lasting brake performance.