The ST-RX825 is Shimano's top-tier GRX Di2 wireless dual-control lever, combining electronic front shifting with hydraulic disc braking in a single ergonomic unit. This J-kit pairs the left-hand lever with the BR-RX820 rear caliper — everything you need to complete the rear brake circuit on a 2x12-speed GRX Di2 gravel build.

Highlights

• Wireless Di2 shifting: no shift cables, for a clean cockpit and reliable electronic front gear changes.
• SERVO WAVE braking: reduces idle lever travel so pads engage sooner, delivering rapid power and precise modulation on gravel and dirt descents.
• Three programmable Di2 buttons: two shift paddles plus a thumb-side button — all configurable via the E-TUBE Project Cyclist app to match your preferred shift mapping.
• Gravel-optimised hood shape: raised horns, ribbed texture, and anti-slip coating work equally well with traditional drops or flared gravel bars.
• CR1632 coin cell batteries: approximately 3.5–4 year lifespan with low maintenance overhead.
• CFRP lever housing: carbon fibre reinforced plastic keeps weight low without sacrificing stiffness.
• BR-RX820 2-piston caliper: 10% wider pad clearance versus previous GRX for reduced brake noise and consistent power.
• ONE WAY BLEEDING system: simplified mineral oil bleed procedure for clean, quick field maintenance.
• Flat mount rear: compatible with 140 mm and 160 mm rotors (adapters sold separately for 160 mm).

ST-RX825 Lever Technology

Shimano's SERVO WAVE mechanism shortens the idle portion of lever travel so brake pad engagement happens earlier in the stroke — you spend more of the lever's range generating actual braking force. The lever body is designed with a gravel-first profile: the raised hood horn and ergonomic ribbing provide a secure grip across varied terrain and weather, and the clamp band diameter of 23.8–24.2 mm fits standard drop-bar clamp sections. An EW-SD300 wired port and a satellite shifter port allow connection to sprint levers or bar-end buttons for further cockpit customisation.

BR-RX820 Rear Caliper

The BR-RX820 is a two-piston hydraulic disc caliper engineered for GRX gravel use. Its 10% wider pad clearance compared to the previous generation reduces pad rub and brake noise on rough terrain. Shimano's ONE WAY BLEEDING port simplifies the bleed process — less mess, less time, and a more consistent result in the field. The caliper ships with L05A-RF finned resin pads for improved heat dissipation, and is also compatible with K05S-RX resin and L04C-MF metal-fin pads for more demanding conditions. The pre-fitted SM-BH90-JK-SSR brake hose is 1700 mm in length, suited to the rear circuit of most gravel and road frames.

Compatibility & Fit

This is the left-hand lever — in Australian setup the left lever operates the rear brake. The ST-RX825 is designed exclusively for Shimano 2x12-speed Di2 GRX groupsets. Compatible front derailleurs: FD-RX825, FD-R9250, FD-R8150, FD-R7150. Compatible rear derailleurs: RD-RX825, RD-R9250, RD-R8150, RD-R7150. Compatible calipers include BR-RX820, BR-RX400, BR-R9270, BR-R8170, and BR-R7170. Brake fluid: Shimano mineral oil only — do not use DOT fluid. Caliper mount: flat mount rear (25 mm frame mount, no adapter required).