Shimano GRX RX825 Di2 Rear Derailleur

The Shimano GRX RX825 Di2 Rear Derailleur is the 12-speed electronic derailleur at the top of Shimano's GRX gravel groupset, built for 2x drivetrains that need to shift cleanly across rough, inconsistent terrain. It uses Shimano's Shadow RD+ design with a switchable clutch: flip it on and the derailleur cage holds steady over chatter and impacts, cutting chain slap and dropped chains on washboard and singletrack; flip it off and the wheel comes out easily for a quick tube change or transport.

As part of Shimano's Di2 system, the RX825 shifts wirelessly from the shift levers while staying wired to the battery, and it is the communication hub of the drivetrain, talking to compatible cycling computers and the E-TUBE PROJECT app for setup, firmware updates, and shift customization on the fly. It is built around 12-speed cassettes up to 34T or 36T, giving riders enough low-end range for loaded gravel climbs and technical grades without dropping to a 1x setup. At 310 grams, it adds minimal weight to a gravel build while carrying the same shifting precision Shimano's road Di2 derailleurs are known for, tuned instead for the wider gearing range and rougher use case gravel riding demands.