Shimano GRX Di2 1×12 in the first test: The Japanese manufacturer's new gravel components were on display for the first time at Eurobike 2025. Velomotion did a few laps on the Orbea Terra and was impressed by the excellent performance of the new wireless rear derailleur.
The gravel community has been waiting for it for a long time – and it was on display at Eurobike 2025: After several years of offering an electronic GRX with a double chainring, Shimano finally released the 1x version of the successful gravel component group. And it offers some interesting new features.
New rear derailleur based on Deore XT
The rear derailleur of the GRX Di2, called the RD-RX827-SGS, isn't entirely new: except for the design, it's identical to the "Deore XT Di2" derailleur introduced a week earlier for the MTB segment. But that's just a side note, because more importantly, the device ushers in a revolution: For the first time, Shimano shifting systems are completely wireless. While the GRX Di2 2×12 (as with current road bike groupsets) already featured wireless brake and shift lever communication, these components still had a central power supply. The new GRX Di2 1×12 doesn't have a front derailleur that needs to be connected to a shared battery—so the battery can be installed directly in the rear derailleur, as has been the case for years with SRAM and, more recently, with Campagnolo.
It is mounted in a slot on the underside of the changer, which is closed by a flap. This is released with a small lever, then the battery can be removed for charging, which takes place every 700 to 1.000 km is required. The battery placement is well-designed and ensures that the rear derailleur appears comparatively compact.
Battery fully integrated into the rear derailleur
On the rear of the derailleur are the typical stop screws for limiting lateral travel. And, of course, the new derailleur is designed for traditional derailleur hanger mounting, rather than direct frame mounting like the models from its major competitor.
Optionally with pure brake handle on the left
The cockpit hasn't changed, at least not on the test bike: The distinctive, ergonomically very comfortable Di2 shifters of the GRX are also used on the 1x12 bike. This is interesting because there are now three buttons per lever, which can be assigned as desired. One disadvantage of the Di2 levers is still that the buttons integrated into the brake lever are close together, and it's difficult to always hit the right one when wearing gloves. Now you can configure the buttons à la SRAM – the right lever shifts up, the left down. With the additional buttons on the inside and top of the grip body, you can cycle through a bike computer or operate the rear derailleur.
But do you need two shifters for one rear derailleur? No, because Shimano now also offers a brake-only lever in the form of the GRX Di2. However, it costs just as little as the brake-shift lever, so you might as well choose the option with more features.
Curiously, the GRX rear derailleur is only available with a long cage, while the XTR and XT MTB derailleurs are also available in a medium-length version. The GRX Di2 is optimized for cassettes with a 10-tooth top sprocket, so there are currently two options: 10-51 and 10-45. The 9-45 cassette of the Shimano XTR is not approved. The 1x crankset of the GRX will, of course, continue to be offered only with 40 or 42 teeth – the resulting highest possible gear might not be long enough for racers.
Two cassettes, two chainrings
Interestingly, at least two bike manufacturers are not using the new GRX Di2 1x quite as intended: Canyon is fitting the Deore XT rear derailleur and 8-9 cassette to the new Grizl CF45; Cervélo is combining the GRX rear derailleur and 10-51 cassette with a 48-tooth WolfTooth chainring.
The precise gear shifts familiar from the GRX Di2 2×12 system are also available in the new 1x system. The electronic rear derailleur shifts the chain from one sprocket to the next lightning-fast and extremely quietly – even in the uphill gears with up to six teeth difference.
In addition to its perfect functionality, the system also offers a very clean look thanks to the elimination of cabling; it also makes converting from a mechanical shifting system more attractive. The costs are, of course, not insignificant: The GRX Di2 rear derailleur costs around €490; a set of Di2 shifters costs around €900. And of course, you need a wheelset with a MicroSpline freehub – the test bike was fitted with the GRX WH-RX880-TL, which weighs around 1.450 grams thanks to its carbon rims and has a recommended retail price of €1.650.
The new components should be available during the summer; complete bikes are also already in the starting blocks from several suppliers.