The Shimano GRX Di2 electronic gravel drivetrain is going 12-speed with new three-button shifters and new derailleurs. Like other Di2 systems, this one uses a central battery to power the front and rear derailleurs, while the shifters are powered separately and communicate wirelessly. Shimano is pitching the new 12-speed GRX Di2 system as a 2×12 system, though presumably, it could be set up 1×12 using an existing RX820-1 or RX610-1 12-speed crankset.
The biggest change from 11-speed GRX Di2 seems to be at the levers. The new shift levers feature three buttons per side, and buyers can customize what each button does. In addition to controlling shifts, the buttons can be set up to turn on a light or switch screens on a GPS unit. A firmware update to both 12- and 11-speed GRX Di2 groups adds the ability to use a single button to toggle the front derailleur back and forth rather than needing to have separate buttons for shifting up and down.
In addition to the changes under the hood(s), the shape of the Shimano GRX 12-speed shifters is said to be more round and optimized for flared bars. The weight of two shifters is 415g, though it’s not clear if that includes the two coin-cell batteries that are meant to last about 3.5-4 years.
The rear derailleur for the 12-speed GRX Di2 drivetrain gets an extra click over the 11-speed version and features the same Shadow RD+ clutch. The charge port for the system is located on the rear derailleur, which weighs 310g.
Finally, there’s a new 12-speed-specific GRX Di2 front derailleur that is said to weigh 142g. With the Shimano E-TUBE PROJECT Cyclist app, users can configure the front derailleur to shift in concert with the rear in Synchronized and Semi-Synchronized shift modes.
Shimano announced their 12-speed GRX gravel groupset in August of last year. The brand currently offers a 12-speed eMTB electronic drivetrain, but the electronic drivetrain for non-electric mountain bikes is still limited to 11 speeds and is due for an update.
