Purpose-built for gravel and mixed-terrain riding, the Shimano GRX BL-RX610-L hydraulic brake lever and BR-RX400 rear disc brake caliper deliver consistent, powerful braking across demanding conditions. Designed around single-chainring drivetrains, this matched brakeset pairs a tactile, ergonomic lever with a proven two-piston flat mount caliper — factory pre-bled via Shimano's J-Kit system and ready to install straight out of the box.

Highlights

• GRX 12-speed dedicated brake lever: BL-RX610-L left-hand hydraulic lever for rear brake control — ideal for 1x gravel builds with a separate shifting setup.
• BR-RX400 two-piston flat mount caliper: proven GRX-grade hydraulic caliper for consistent, fade-resistant stopping power.
• Factory pre-bled J-Kit: SM-BH90-JK-SSR hose and caliper arrive pre-bled — no bleeding required on first installation.
• Reach Adjust: lever distance from the bar can be dialled in to suit any hand size without tools.
• ICE Technologies: three-layer clad rotor and pad technology dissipates heat efficiently for consistent feel on long descents.
• L05A-RF resin pads with fin: included pad compound provides excellent modulation and quieter operation in wet or muddy conditions.

Lever Detail

The BL-RX610-L is a standalone hydraulic brake lever — not a combined shifter — making it the natural companion for 1x gravel builds where bar space is reserved for a dropper remote or bar-end shifter. The textured hood and anti-slip lever surface maintain confident grip in wet or muddy gravel conditions. Clamp diameter is 23.8–24.2 mm to fit standard drop and flared gravel bars. Oil type is Shimano Mineral (not DOT fluid).

BR-RX400 Caliper

The BR-RX400 is a two-piston flat mount hydraulic caliper from Shimano's GRX gravel groupset. Its low-profile design integrates cleanly with modern flat mount frames and forks. The One-Way Bleeding system simplifies future maintenance — air can be purged quickly through a single port, getting you back on the road or trail faster. Includes L05A-RF resin pads with cooling fin as standard.

Compatibility & Fit

Designed for flat mount disc frames and forks. Compatible with Ø140 mm, Ø160 mm, and Ø180 mm rotors (adapter required for 180 mm — sold separately). Works with Shimano GRX-compatible rotors; rotor is sold separately. Uses Shimano Mineral Oil only — do not use DOT fluid. In Australian bicycle convention, the left-hand lever controls the rear brake. Compatible with GRX 12-speed drivetrains.