The Shimano GRX ST-RX400 is a left-hand dual control lever purpose-built for gravel and mixed-terrain riding. It integrates 2-speed front derailleur shifting with hydraulic disc braking into a single ergonomic unit, giving gravel riders confident, responsive control on everything from sealed roads to rough dirt tracks.

Highlights

• Gravel-specific hood geometry: A raised hood profile keeps hands from sliding forward on rough terrain, reducing fatigue on long days in the saddle.
• Hydraulic disc braking: Runs on Shimano mineral oil for powerful, modulated braking with low lever effort — even in wet and muddy conditions.
• Anti-slip brake lever texture: Textured lever surface improves grip when hands are wet or gloved, maintaining control on unpaved descents.
• Reach adjust: Tool-based reach adjustment lets riders dial in the distance from bar to lever to suit their hand size and preference.
• Smooth, light shifting: Compatible with GRX 10-speed front derailleurs for positive, low-effort gear changes across the full cassette range.
• Includes Optislick cable & OT-SP41 housing: Ships with Shimano's low-friction shift cable and housing for crisp, consistent front shifting out of the box.

Gravel-Ready Design

The GRX groupset was engineered from the ground up for off-road and mixed-surface riding. The ST-RX400 lever reflects this with an ergonomic hood shape that naturally positions the wrist for long gravel rides, and a rotary brake axle positioned higher than equivalent road levers, which improves braking leverage and feel when riding on the hoods.

Hydraulic Brake System

The ST-RX400 integrates a hydraulic master cylinder directly into the lever body, operating on Shimano mineral oil. This delivers consistent brake feel that doesn't degrade with heat or repeated use. The lever pairs with Shimano flat-mount disc brake calipers including the BR-RX400, and is also compatible with Shimano road hydraulic calipers from the Tiagra, 105, Ultegra, and Dura-Ace ranges.

Compatibility & Fit

This is the left-hand lever controlling the front derailleur (2-speed / front shifting) and the rear brake (Australian convention: left lever = rear brake). Designed for 2x10-speed GRX drivetrains. Compatible front derailleurs include the FD-RX400 (GRX) and FD-4700 (Tiagra). Compatible rear derailleurs include the RD-RX400 and RD-4700. Handlebar clamp diameter: 23.8–24.2 mm (standard drop bar). Brake hose and caliper are not included — system requires professional hydraulic bleed during installation.