Shimano GRX is now a very well established part of the gravel scene and while last year saw the launch of the cable 12 speed GRX, we are now seeing the launch of the 12 speed Di2 version. The main changes, apart from the addition of another cog, are a redesigned bonnet to better fit the widened bars and added button functionality as well as the ability to use the satellite shifter.
Like Dura-Ace, Ultegra and 105, the new GRX Di2 (Shimano-coded RX825) is semi-wireless, with wireless controls on the hoods but a hard connection between the battery and the front and rear derailleurs. While we recently saw a patent for a fully wireless, 13-speed Shimano drivetrain, it’s at least clear now that it wasn’t the new GRX.
For convenience, the new components have been divided into individual components.
The hoods look very similar but are slightly larger and are intended to better fit the flared bars (Image credit: Shimano)
Hood
At first glance, you’d be hard-pressed to find any differences between the new hoods and the old Di2 from the 11-speed setup. 11-speed hoods have been universally popular in our experience, and Shimano doesn’t seem to have seen any point in rebuilding something people like.
The same ribs exist on the hood covers for better grip on rough terrain, and the “lump” still has that characteristic, almost curved rear peak. However, it has a larger diameter to create a smoother transition from the rod to the shifter and reduce pressure points.
The anti-slip coating on the lever also remains, and the lever still breaks more than road levers to work better with the extended bars. The thumb button on the top inside of the headset is still available to act as a satellite scroller or to control computer screens. According to the cable kit, the housings are designed to be flat when mounted on extended bars.
A new addition to the hoods is a battery status light on top of the front shifter knob, so you can easily see when the coin cell batteries that power the shifter need to be replaced.
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The chainset and cassettes are carried over from the 12sp cable group (Image credit: Shimano)
Chain and gear ratios
Shifting is now 2×12, but as this kit shares the cranks supplied with the cable operated 12sp GRX, it stands to reason that the current 1x crank on offer for cable users will be compatible with the Di2 version. However, this is not mentioned in the press material.
The 12sp Di2 chainset is the same as the 12sp cable model, with the same 48/31 tooth setup offered by the current 11sp, and is compatible with the smaller 46/30 chainset from the 12sp cable operated GRX. The new chainset itself looks similar to the current 11spd model, but more material is made from the outer chainring.
Cartridge options are either 11-36t or 11-34t, depending on whether customers want more range or tighter spacing. These are the same parts as on the cable kit.
The front derailleur loses the silver front panel and has an extra cutout on the inner plate, but is otherwise identical (Image credit: Shimano)
Front derailleur
The front derailleur is again strikingly similar to its predecessor. The chainline remains 2.5mm wider than on the road for slightly improved clearance. The front panel of the main motor unit is no longer silver, but all black, and the inner plate has an additional cutout to shed a few grams.
Now all black, the rear derailleur kicks up further and has more cutouts to reduce weight, losing the parallelogram cutouts (Image credit: Shimano)
Rear derailleur
Strangely, the rear derailleur seems to have added material. The outer plate of the central parallelepiped is no longer machined, but is now solid. The whole thing is now all black and has the same Shadow setup as before, with a clutch switch that makes removing the wheel easier.
The lower cage bends more drastically halfway through its length, has larger cutouts, and appears to have a larger bottom support wheel, again with larger cutouts. The charging port also remains on the back of the rear derailleur, in line with the rest of the Di2 family.
The previous derailleur has a maximum capacity of 42t and although not listed, this is not expected to change.
The brakes are also carried over from the 12sp cable group, bringing a 10% wider pad gap to the electronic system to help reduce pad wear. (Image credit: Shimano)
Brakes
The brakes are identical to the brakes on the 12sp cable kit. This marks an improvement over the current 11sp, as the GRX BB-R820 calipers feature Shimano’s ‘Servo Wave’ brake technology, which places the pads further apart and takes up more of the pad’s movement on the initial lift of the lever. This should reduce pad chafing – something more common in off-road driving – and improve modulation.
Satellite shifts are now supported along with a system where one button can be programmed to shift the derailleur in and out. (Image credit: Shimano)
Functionality of buttons and satellite sorting
This latest iteration of the GRX Di2 is now compatible with satellite shifters, either on the bar or at the end of the bar for those gravel riders who use TT bars. More than that, the buttons on this groupset are now more programmable than ever.
Using the Shimano E-Tube app, riders can assign a single button to shift the derailleur in either direction, freeing up the button for other functions such as controlling computer screens, bike functions or compatible lights.
Deore XT pedals, dressed in a gravel outfit (Image credit: Shimano)
Pedals
Not new in terms of hardware, but new in terms of visuals; the new GRX Di2 also matches the GRX edition PD-M8100 pedals, the same as the Deore XT model from Shimano’s MTB range, but with gravel-inspired graphics.
Prices and weights
Prices and weights, where information has been provided, are listed below. We will update as more information becomes available.
