Shimano's new GRX Di2 takes 2x electronic shifting off-road
Shimano has done what many gravel riders dreamt of, bringing electronic shifting to ultra wide range gravel bike drivetrains.
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The Japanese brand’s new GRX RX825 Di2 combines the proven components of its GRX gravel drivetrain with the electronic bits of Di2. For gravel bike riders who want the topography-conquering ability of a 2x drivetrain, with the precision shifting of electronic gear selection, this GRX RX825 Di2 system could be ideal.
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‘Wired where required’
Like Shimano’s Di2 road drivetrain, the electronic GRX system isn’t fully wireless, but a hybrid set-up.
Primary battery power connects to the 2x system’s two derailleurs with tiny wires, and there’s a central port to recharge instead of removing batteries from the individual drivetrain components, like some other truly wireless drivetrains. Replaceable coin cell batteries serve the lever sensor electronics with an estimated operational endurance of three to four years.
2024 shimano grx di2 2x hero 2-2.jpg, by Liam Mercer
True to its purpose as an off-road touring and adventure drivetrain, Shimano’s industrial designers have given the GRX RX815 Di2 levers a ribbed anti-slip surface treatment. The brake levers are shaped to integrate seamlessly with wide, flared, gravel bike handlebar geometries. To reduce hand strain when rolling large distances on challenging off-road routes, the GRX Di2 levers are rounded in shape with more surface area, created to reduce point load issues into a rider’s palms.
2024 shimano grx di2 2x hood inner-2.jpg, by Liam Mercer
Electronics within the GRX Di2 system have other benefits besides effortlessly crisp shifting. Accessory shift buttons allow gravel riders to trigger additional functions without moving their hands. A third Di2 button is positioned inside the hood, where it can be repurposed as an alternative shifter for either derailleur, as a scrolling trigger for your cycling computer, lap timer button or light switch. Perhaps there might be a wireless dropper post in the works from Shimano's component brand PRO too.
What are your gearing choices?
The appeal of a 2x drivetrain is gearing spread and Shimano’s new electronic gravel set-up has many options. Up front riders can choose two crankset options, either the 48/31t RX820 crank or the 46/30t RX610 crank for steeper terrain. Compatible cassette choices are an 11-36t HG710 or 11-34t, available in three grades: R9200, R8100, R7100.
2024 shimano grx di2 2x front mech-2.jpg, by Liam Mercer
To ensure chain security when rolling across rougher gravel bike routes, the RD-RX825 rear derailleur features Shadow+ chain tension technology, proven on Shimano’s mountain bike drivetrains.
With its simple clutch system, riders can be confident in their chain remaining on-gear when rolling over the roughest terrain. When the rear wheel requires removal to fix a puncture, for some DIY servicing or bike transport, it’s easy to remove, with the chain slackening immediately when the Shadow+ lever is disengaged. Shimano’s RD-RX825 derailleur weighs only 310g.
2024 shimano grx di2 2x mech-2.jpg, by Liam Mercer
The front derailleur is a rarity in off-road riding, making the electronic shifting FD-RX825 so novel. It weighs only 142g and features, unlike a road bike front derailleur, features a +2.5mm chain line, to account for the trends towards wider gravel bike tyres. Shimano’s reference drivetrain to wheel clearance was modelled on a 25mm internal diameter gravel bike wheel rim.
2024 shimano grx di2 2x brake cali-2.jpg, by Liam Mercer
For 2x drivetrain believers who value the benefits of generous gearing spread with tiny steps in between, Shimano’s GRX RX825 Di2 will have real-world appeal. But what does a 2x electronic drivetrain for rugged gravel and drop bar adventure riding cost?
The integrated RX825 shifters and brakes are £400 a side, with a front mech pricing at £185 and the rear derailleur at £325. If you want to purchase the shifters only, they are £300 a side. Batteries are a consideration with any electronically assisted drivetrain, and the GRX RX825 Di2’s 3-port internal battery costs £175.
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