Shimano GRX is now an integral part of the gravel scene. Last year a GRX with 12 speeds and cable was introduced, now the 12-speed Di2 version follows. In addition to an additional sprocket, the most important changes are a revised hood design that harmonizes better with flared handlebars, additional button functions 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 hardwired connection between the battery and the front and rear derailleurs. Although we recently saw a patent for a fully wireless 13-speed Shimano groupset, it’s now at least clear that this wasn’t a new GRX.
For simplicity, the new components have been broken down into their constituent parts.
The hoods look very similar, but are slightly larger and are intended to fit the flared handlebars better (Image credit: Shimano)
Hoods
At first glance, it’s hard to tell the difference between the new hoods and the old Di2 hoods on the 11-speed groupset. The 11-speed groupset has been generally popular in our experience, and it seems Shimano has seen little point in redesigning something that people like.
The same ribs are present on the hood covers to improve grip on rough terrain and the ‘onion’ still features the characteristic, almost hook-shaped rear tip, but the diameter is larger to create a smoother transition from handlebar to gear lever and reduce pressure points.
The anti-slip coating on the lever also remains and the lever still bends out more than on street levers to work better with flared bars. The thumb button on the top inside of the knob shield is still there to serve as a satellite switch or to control computer screens. As with the cable group, the hoods are designed to be flat when mounted on flared bars.
A novel addition to the hoods is a battery level indicator on top of the front shift knob, so you can easily see when you need to replace the coin cell batteries that power the shift levers.
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The chain set and cassettes are taken over by the 12-speed cable group (Image credit: Shimano)
Chain set and gear ratios
The gearing is now 2×12, but since this groupset has the same cranksets that come with the cable-actuated 12-speed GRX, it stands to reason that the 1x crankset currently offered to cable users would be compatible with the Di2 version, but this is not mentioned in the press material.
The 12-speed Di2 chainset is the same as the 12-speed cable model, with the same 48/31 tooth configuration as the current 11-speed model, and is also available with the smaller 46/30 chainset from the 12 -compartment cable GRX compatible. The new chainset itself looks similar to the current 11-speed model, but more material has been carved out of the outer chainring.
Cassette options are either 11-36t or 11-34t depending on whether the customer wants a wider bandwidth or a smaller spacing. These are the same parts as the cable group.
The derailleur loses the silver front plate and has an additional cutout on the inner plate, but is otherwise identical (Image credit: Shimano)
Front derailleur
The front derailleur also bears a striking resemblance to its predecessor. The chainline remains 2.5mm longer than on the road, resulting in slightly improved clearance. The front of the main motor unit is no longer silver, but completely black, and the inner plate has an additional cutout to save a few grams.
The rear derailleur is now all black, features a larger return and has more cutouts to save weight, while eliminating the parallelogram cutouts. (Image credit: Shimano)
Rear derailleur
Strangely, the rear derailleur seems to have more material in it. The central outer parallelogram plate is no longer milled but solid. The whole thing is now completely black and features the same shadow setup as before, with a switch for the clutch to make it easier to remove the wheel.
The lower cage bends more toward the rear halfway along, 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, in keeping with the rest of the Di2 family.
The previous rear derailleur had a maximum capacity of 42 teeth and although this is not listed, it is not assumed that this has changed.
The brakes have also been adopted from the 12-speed cable group, which brings a 10% larger pad clearance to the electronic system to reduce pad friction (Image credit: Shimano)
Brakes
The brakes are identical to those on the 12-speed cable group. This is an improvement over the current 11-speed group, as the GRX BB-R820 calipers feature Shimano’s ‘Servo Wave’ braking technology, which places the brake pads further apart and absorbs more of the pad movement on the initial lever stroke. This should reduce brake pad rub – something that is more common when riding off-road – and improve modulation.
Satellite shifters are now supported, along with a system where a button can be programmed to turn the derailleur on and off (Image credit: Shimano)
Button function and satellite shift lever
This latest version of GRX Di2 is now compatible with satellite switches, either on the handlebar or at the bar end for gravel riders who use TT bars. In addition, the buttons on this groupset are now more programmable than ever before.
Shimano’s E-Tube app allows riders to 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 lights.
Deore XT pedals in gravel outfit (Image credit: Shimano)
Pedals
Not new in terms of hardware, but new in terms of looks; the new GRX Di2 also coincides with a GRX edition of the PD-M8100 pedals, just like 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 listed below. We will update as more information becomes available.
