Shimano GRX Di2 RD-RX825

12-Speed Di2 Precision. Integrated Chain Control.

The engineering centerpiece of the Shimano GRX RD-RX825 Derailleur is its integrated Shadow RD+ chain stabilizer. Featuring a convenient ON/OFF switch, the mechanical clutch applies firm tension to the derailleur cage to prevent chain bounce and chainring drops over technical surfaces. Built as the central hub of Shimano’s wireless Di2 system, the RD-RX825 houses the system’s charging port, LED status indicator, and wireless transmitter. Sending instant, precise signals to the front derailleur and shift levers without needing an external junction box.

Why the GRX RD-RX825 Belongs on Your Gravel Bike:

• 12Speed Di2 Electronic Precision: Delivers instantaneous, hyper-accurate shifts across 11-34T or 11-36T 12Speed cassettes with zero shift cables to stretch, wear, or contaminate with trail mud.

• Integrated Shadow RD+ Chain Stabilizer: Engageable clutch mechanism keeps the chain taut over severe chatter, practically eliminating chain slap and drive-side chainstay damage.

• Central Wireless & Charging Hub: Features an integrated magnetic charging port and wireless connectivity (Bluetooth LE / ANT+), allowing seamless pairing with the E-TUBE PROJECT app for custom button mapping and firmware updates.

• Low-Profile Shadow Architecture: Keeps the derailleur body tucked tightly under the chainstay and cassette, protecting it from flying gravel, trail debris, and side impacts.

• Durable Alloy Construction: Built with high-strength aluminum link arms and a rigid pulley cage designed to withstand severe gravel racing and bikepacking conditions.

Technical Specifications:

• Series: Shimano GRX RX820 / RX825 Di2 Series

• Drivetrain Speed: 12Speed Electronic

• Cassette Capacity: 11-34T to 11-36T

• Maximum Front Difference: 17T (Optimized for GRX 48/31T and 46/30T 2x Cranksets)

• Chain Stabilization: Shadow RD+ Mechanical Clutch (With ON/OFF Switch)

• Connectivity: Wireless Di2 Protocol / Bluetooth LE / ANT+

• System Charging: Magnetic EW-EC300 Charging Port

The Alegro Perspective: In the service bay, the RX825 derailleur is the beating heart of modern 12Speed Di2 gravel setups. Putting the charging port and wireless transmitter directly into the rear derailleur simplifies frame routing immensely no more buried junction boxes inside the seatpost or downtube. When you flip the Shadow RD+ clutch switch ON, the drivetrain becomes completely silent on rough gravel descents. It’s rock-solid, ultra-fast, and built to handle the worst weather and mud you can throw at it.

Instant Electronic Shifting. Total Chain Security. Master Modern Gravel with Shimano.