Shimano GRX is now a well-established part of the gravel scene, and while last year saw the launch of a wired 12-speed GRX, we are now seeing the launch of a 12-speed Di2 version. The main changes, in addition to the addition of an extra cog, are a revised hood design to better suit flared bars, and added button functionality and the ability to use satellite switches.
Like Dura-Ace, Ultegra and 105, the new GRX Di2 (RX825 in Shimano coding) is semi-wireless, with wireless controls on the hoods, but a wired connection between the battery and the front and rear derailleurs. Although we recently saw a patent for a fully wireless Shimano 13-speed groupset, at least it’s now clear that this wasn’t a new GRX.
For convenience, the new components have been broken down into their component parts.
The caps are very similar, but are slightly larger and are intended to better fit flared bars (Image credit: Shimano)
Cut
At first glance it would be difficult to find the differences between the new hoods and the old Di2 hoods from the 11-speed groupset. The 11-speed hoods have been universally popular in our experience, and it seems like Shimano has little appetite for overhauling something that people like.
The same ribs are present on the bonnet covers for improved grip on rough terrain, and the ‘pommel’ still has that characteristic almost hooked flap at the rear. However, it has a larger diameter, to create a smoother transition from handlebar to shifter and reduce pressure points.
The anti-slip coating on the lever also remains, and the lever still flexes more than road levers, to work better with flared bars. The thumb button on the top inside of the pommel peak is still there, to work as a satellite shifter or to control computer screens. According to the cable groupset, the hoods are designed to be flat when mounted on flared bars.
A new addition to the engine covers is a battery level indicator light on top of the front shift lever, making it easy to see when to replace the coin cell batteries that power the shift levers.
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The crankset and cassettes are taken from the 12sp cable groupset (Image credit: Shimano)
Crankset and gear ratios
The gearing is now 2×12, but since this groupset shares the cranksets that come with the cable-driven 12sp GRX, it stands to reason that the current 1x crankset offered to cable users would be compatible with the Di2 version. However, this is not mentioned in the press material.
The 12sp Di2 crankset is the same as the 12sp cable model, with the same 48/31 tooth setup that the current 11sp offers, and is also compatible with the smaller 46/30 crankset of the 12sp cable-driven GRX. The new chainset itself is similar to the current 11spd model, but more material has been incorporated from the outer chainring.
Cassette options include an 11-36t option or an 11-34t option, depending on whether customers want longer range or shorter distance. These are the same parts as on the cable groupset.
The front derailleur loses the silver front panel and has an additional cutout on the inner plate, but is otherwise identical (Image credit: Shimano)
Front derailleur
The front derailleur again bears a striking resemblance to its predecessor. The chainline remains 2.5mm wider than on the road, for slightly better clearance. The front-facing panel of the main motor unit is no longer silver, but all black, and the inner plate has an extra cutout to shed some grams.
Now all black, the rear derailleur steps further back and has more recesses to help shed weight, while losing the parallelogram recesses (Image credit: Shimano)
Rear derailleur
Oddly enough, the rear derailleur appears to have added material. The central parallelogram outer plate is no longer machined, but is now solid. The whole thing is now all black and features the same Shadow setup as before, with a clutch switch to make wheel removal easier.
The lower cage buckles more drastically to the rear mid-length, has larger cutouts, and appears to have a larger lower jockey wheel, again with larger cutouts in it. The charging port also remains on the back of the rear derailleur, as with the rest of the Di2 family.
The previous rear derailleur had a maximum capacity of 42 tonnes, and although not listed this is not expected to have changed.
The brakes are also carried over from the 12sp cable group, creating a 10% increase in brake pad spacing in the electronic system to help reduce brake pad rubbing (Image credit: Shimano)
Brakes
The brakes are identical to those of the 12sp cable groupset. This marks an upgrade over the current 11sp, as the GRX BB-R820 calipers feature Shimano’s ‘Servo Wave’ braking technology, which places the brake pads wider and takes up more of the pad travel on the first lever stroke. This should reduce brake pad friction – something more common in off-road driving – and improve modulation.
Satellite shifters are now supported, along with a one-button system that can be programmed to both engage and disengage the front derailleur (Image credit: Shimano)
Button functionality and satellite shifters
This latest version of GRX Di2 is now compatible with satellite shifters, both on the handlebar and on the handlebar end, for those gravel riders using TT handlebars. But even more: the buttons on this groupset are now more programmable than ever.
Using Shimano’s E-Tube app, riders can assign a single button to shift the front derailleur in either direction, freeing up a button for other functions such as controlling computer screens, lap functions or compatible lighting.
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 coincides with a GRX edition of the PD-M8100 pedals, the same as the Deore XT model from Shimano’s MTB line, but with gravel-inspired graphics.
Prices and weights
Prices and weights, where information has been provided, are set out below. As more information becomes available, we will update this.
