Shimano RD-RX400 GRX 10-speed rear derailleur, Shadow+, for double
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Our price £46.74
Following a comprehensive research, testing and development process, bringing together global feedback from riders on trails, bridleways, pavement and paths at all levels of competitiveness, Shimano introduces a new component series known as GRX; the world’s first dedicated family of gravel/adventure components built for both fast riding and assured capability on loose surfaces.
GRX offers RX800, RX600 or RX400-series components with 1×11, 2×11 and 2×10 drivetrains and mechanical and Di2 electronic shifting options, allowing riders to tailor their mixed surface riding experience and explore beyond their usual limits to pursue a wide range of terrain.
Developing the series took Shimano’s development team well outside traditional confines to create a platform that addresses riders’ needs now and into the future. Be it gravel riding, modern adventure road riding, bikepacking, or fulfilling the needs of discerning cyclocross racers, SHIMANO GRX provides options ranging from gravel-tuned gearing ratios to custom ergonomics, from dropper post integration to gravel-specific GRX wheels with wider rim profiles.
Diving into the detail, GRX includes three crankset options – 1×11, 2×11 or 2×10-speed – plus front and rear derailleurs, disc brake calipers with an in-line brake lever option, and left and right STI hydraulic levers, coming in either Di2 shifting or mechanical shifting options.
These components employ Shimano’s class-leading drivetrain technologies from both the road and mountain bike side to deliver the hallmark shifting precision and stability for which the company is known. With GRX the net result is a smooth and quiet-running drivetrain that is specially tuned for the unique characteristics of gravel terrain, riding positions and gravel bicycle designs.
For simplicity, Shimano GRX recommends using Shimano MTB (Deore XT, SLX or Deore) or Road (Ultegra, 105, Tiagra) cassettes and chains that already exist in the Shimano lineup. In addition to the category-leading Shimano GRX 800 series, there are also more affordable 11-speed components, a 600-series crank and set of shifters, which can be mixed seamlessly with 800-series parts, and 10-speed cranksets, derailleurs and shifter/brakesets. This means that you can create everything from a light-weight racing-level GRX stead at the premium level to a leisure-riding GRX workhorse at the more economical level.
GRX Cranksets: 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.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. All front derailleurs provide Shimano’s legendary front shifting performance. Shimano Di2 FD’s can be perfectly adjusted using Shimano’s simple and integrated controls whilst mechanical FD’s bring an extremely light front shifting feeling with an ergonomic power curve, toggle link construction for more cable routing options and an integrated cable tension bolt for precise and easy adjustments.
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/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 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 1×11 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 1×11-specific RX800 and RX600-series left side hydraulic disc brake levers with no dropper or shift internals, including the 1×11 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) offer 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 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 to deliver powerful brake performance, taking features like one-way bleeding and ICE TECHNOLOGIES heat-dissipating finned brake pads and rotors to offer efficient cooling and long-lasting brake performance.
To complete the experience, Shimano tips its cap to the experimental spirit of gravel with two gravel/adventure-inspired 12mm E-THRU axle wheel sets (WH-RX570-TL-F12/R12). The 700c or 650b (non-Boost) tubeless-ready wheelsets offer 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.
Overall, with the multiple options and specifications available, GRX has a broad appeal and a broad message to riders of all disciplines.
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