SHIMANO GRX DI2 RD-RX825 REAR DERRAILLEUR 2 X 12 36T MAX

Experience the benchmark in mixed-terrain electronic shifting with the Shimano GRX Di2 RD-RX825 Rear Derailleur. Engineered specifically for modern 2x12-speed gravel drivetrains, this premium component pairs seamlessly with Shimano's wireless dual-control levers while wiring directly into a central internal seatpost battery. This smart architecture ensures rock-solid electronic reliability, hyper-fast shifting execution, and an incredibly clean cockpit layout.

Built to conquer demanding off-road terrain, the RD-RX825 features Shimano’s race-proven Shadow RD+ adjustable chain stabilizer clutch. With a simple flip of the external on/off switch, the clutch applies heavy spring tension to the derailleur cage, completely eliminating disruptive chain slap and preventing chain drops over corrugated roads or singletrack sections. It is optimized to work flawlessly with 11-34T and 11-36T 12-speed cassettes, offering gravel racers and adventure riders a wide gear range with tight, cadence-matching steps to tackle sustained outback climbs or fast bitumen pacelines.

Key Features

• Semi-Wireless Di2 Connectivity: Receives wireless signals from the cockpit shifters while drawing long-lasting, stable power from a central internal battery.

• Shadow RD+ Stabilizer Clutch: Features a gravel-tuned, adjustable internal clutch mechanism that minimizes chain bounce and ensures crisp, silent tracking.

• Integrated Charging and Functionality: Features an onboard charging port, an LED status indicator, and a multi-function button for quick pairing and micro-adjustments.

• Hyperglide+ Gearing Architecture: Engineered for seamless shifting under maximum pedalling loads, matching perfectly with 11-34T and 11-36T 12-speed cassettes.

• E-Tube App Customisation: Fully compatible with the E-Tube Project app, allowing riders to adjust shifting speeds, customize button layouts, and activate Synchronized shifting.

Specifications

• Position on Bicycle: Rear drivetrain

• Drivetrain Compatibility: 2x12-speed systems

• Maximum Low Sprocket: 36T

• Minimum Low Sprocket: 34T

• Top Sprocket Max/Min: 11T / 11T

• Total Capacity: 40T

• Maximum Front Difference: 17T

• Weight: 310g

• Charging Port: Yes (Compatible with EW-EC300 cable)

• Connectivity Unit: Integrated Bluetooth LE & ANT private

✅ Why This Product IS For You

• Dedicated 2x Gravel Racers: Perfect if you love the tight gear jumps and efficient cadence control of a double chainring setup but want flawless, electronic precision.

• Rough Terrain Enthusiasts: Ideal for riders navigating severe gravel corrugations, rocky fire roads, and mild singletrack who require maximum chain security.

• Set-and-Forget Di2 Fans: Great if you want an electronic system with immense battery longevity, requiring fewer charging cycles than competitor wireless systems.

❌ Why This Product May NOT Be For You

• Dedicated 1x Single-Ring Setups: This model is strictly optimized with a 40T total capacity for 2x drivetrains; it cannot clear the massive 45T or 51T cassettes used on 1x12 gravel setups.

• Desire a Fully Wireless Install: Because it must be physically wired to an internal seatpost battery, it requires internal frame cable routing and cannot be mounted as a standalone wireless unit.

BFC PRO TIP

When it comes time to wash your bike or change a rear tyre, remember to flip the gold Shadow RD+ clutch switch to the "OFF" position first. This instantly releases the high spring tension on the derailleur cage, making it incredibly easy to pull the cage back and slide the rear wheel out without fighting the chain. Just remember to flip it back to "ON" before you roll out, or you'll be greeted by an incredibly noisy chain on your first gravel sector!