The Shimano GRX ST-RX610 dual control lever pairs smooth 2x12-speed mechanical shifting with the controlled power of the BR-RX400 2-piston hydraulic disc brake in a single pre-plumbed kit. Designed for gravel and mixed-terrain riding, the left-hand lever handles front shifting and rear braking, giving you confident control whether you're hammering dirt roads or navigating technical descents.

Highlights

• Gravel-tuned ergonomics: Lever and bracket geometry shaped specifically for drop-bar gravel riding, keeping your hands comfortable over long days in the saddle.
• Reach adjust: 13.3 mm of reach adjustment via a 2.5 mm hex key lets you dial in lever position for any hand size or riding style.
• Anti-slip surfaces: Textured hood and anti-slip brake lever coating give you secure grip on rough terrain, even in wet conditions.
• Optislick inner cable: Low-friction cable coating reduces shift effort and keeps front derailleur response crisp.
• 2-piston flat mount caliper: The BR-RX400 delivers progressive, powerful braking with a low-profile flat mount design and Shimano's ICE technology for effective heat management.
• Pre-plumbed J-kit: Lever and caliper arrive connected via a 1700 mm SM-BH90-JK-SSR hose with straight joint — ready for installation with minimal setup.
• Mineral oil hydraulics: Shimano mineral oil is non-corrosive and stable across a wide temperature range, making maintenance straightforward.

Shifting & Braking

The ST-RX610 uses a mechanical shifting mechanism driving 2x12-speed drivetrains via an OT-SP41 outer casing and Optislick inner cable. The brake circuit is fully hydraulic, actuating the BR-RX400 caliper with a straight hose joint for a clean, direct lever feel. Free stroke adjustment is available on the lever to further refine brake feel.

Design & Build

The composite lever body keeps weight low while the aluminium brake lever adds stiffness exactly where braking loads are highest. The closed clamp fits standard 23.8–24.2 mm handlebar diameters. Funnel bleeding at the lever simplifies hydraulic maintenance. The BR-RX400 caliper uses resin pads (L05A-RF with cooling fins) and a one-way bleeding system, and is compatible with SM-RT64 rotors.

Compatibility & Fit

Designed for 2x12-speed GRX drivetrains. Compatible front derailleurs include FD-RX820 and FD-R7100. Compatible rear derailleurs include RD-RX820, RD-RX822, and RD-R7100. Cranksets: FC-RX610-2, FC-RX820-2, and select Shimano road 12-speed cranks. Cassettes: CS-R8101-12, CS-R7101-12, CS-HG710-12. Brake caliper mount: flat mount. Rotor compatibility: SM-RT64 and other Shimano flat mount-compatible rotors (rotor and adapter sold separately). Brake fluid: Shimano mineral oil only. Handlebar clamp: 23.8–24.2 mm. Hose: SM-BH90-JK-SSR (1700 mm, included). This is the left-hand lever; it controls the front derailleur (shifting) and, in Australian configuration, the rear brake.