The Shimano GRX Di2 RD-RX825 brings flagship electronic precision to the gravel world, pairing instant wireless shifting with SHADOW RD+ chain stabilisation so you can charge rough terrain with complete confidence in your drivetrain.

Highlights

• 12-speed Di2 electronic shifting — instantaneous, repeatable actuation every time
• SHADOW RD+ clutch system quietens chain slap on rough gravel and trails
• Built-in wireless connectivity hub — communicates with levers, compatible computers, and E-TUBE PROJECT via smartphone
• Integrated charge port (EW-EC300) and LED status indicator for battery monitoring
• ON/OFF switch for SHADOW RD+ tension — disengage for easy rear wheel removal
• Supports Full Synchronised and Semi-Synchronised shift modes for effortless front/rear coordination
• Supports cassettes from 11-34T up to 11-36T (36T max low sprocket)

Electronic Architecture

Acting as the communication hub of the GRX Di2 system, the RD-RX825 wirelessly coordinates with the ST-RX825 shift levers and pairs with compatible Garmin, Wahoo, and other ANT+/Bluetooth cycle computers via E-TUBE PORT. The integrated charge port accepts the EW-EC300 charger and an EW-SD300 port connects to the BT-DN300 internal battery, while the multi-function button allows on-the-fly adjustment of synchronised shift modes.

SHADOW RD+ Technology

Shimano's SHADOW RD+ clutch applies additional friction to the derailleur pivot, dramatically reducing chain bounce on gravel, cobbles, and rough descents. The external ON/OFF switch lets you flip the clutch off in seconds for wheel changes — no tools, no fuss. When engaged, the mechanism is lighter and more efficient than traditional roller-type chain devices, preserving drivetrain feel while keeping the chain locked down.

Compatibility & Fit

The RD-RX825 is designed for 2×12-speed GRX Di2 drivetrains. It accepts cassettes with an 11T minimum sprocket and up to a 36T maximum low sprocket, with a 40T total capacity and 17T maximum front difference. Recommended cassettes include the CS-R8101-12 (11-34T) and CS-HG710-12 (11-36T). Compatible shifters include the ST-RX825, ST-R9250, and ST-R9270. Use with Shimano 12-speed chains CN-M9100, CN-M8100, or CN-M7100. Direct-attachment (conventional) mount.