Shimano ST-R8170 Left Lever w/BR-R8170 Rear Disc Brake

Precision braking and lightning-fast wireless shifting in one integrated package — the Shimano Ultegra Di2 ST-R8170 left lever and BR-R8170 rear disc brake caliper deliver road-race-level control for every rider, in every condition.

Highlights

• Wireless Di2 electronic shifting: 2x12-speed compatibility with no cables between shifters — clean cockpit, instant response.
• Servo Wave hydraulic disc braking: variable mechanical leverage delivers rapid initial pad engagement followed by smooth, progressive braking power.
• Flat-mount BR-R8170 rear caliper: two-piston hydraulic design with 10% wider pad-to-rotor clearance for quieter, cleaner braking.
• 16.4 mm reach adjust: dial in lever position to suit any hand size without the need for tools.
• Long-life CR1632 battery: up to 1.5–2 years between battery changes per lever, with easy coin-cell replacement.
• One-Way Bleeding system: quick, clean hydraulic servicing with minimal mess.
• Customisable shift modes: Manual, Full Synchro-Shift, and Semi Synchro-Shift programmable via the E-Tube Project app.
• Satellite shifter compatible: supports SW-RS801 series satellite shifters for TT/aero bar setups.

Lever Design & Ergonomics

The ST-R8170 hood features an all-new profile with a raised peak that curves gently inward, giving your palm a more secure resting position on long climbs and technical descents. Three programmable switches per lever let you assign functions to suit your riding style via the Shimano E-Tube Project app. Reach adjust lets you position the lever blade up to 16.4 mm closer to the bar for confident single-finger braking from the drops or hoods — no tools required.

Braking Performance

The BR-R8170 flat-mount caliper pairs Servo Wave technology with a two-piston design, varying the mechanical leverage ratio across the lever stroke. Initial pull rapidly brings the pads to the rotor; braking power then builds in a smooth, controllable curve — no sudden grab or lock-up. The 10% wider pad-to-rotor clearance compared to the previous generation reduces noise from minor rotor flex, making this the quietest Ultegra disc brake system to date. Easy Hose Joint (J-Kit) simplifies hose installation at the bench or on the road.

Compatibility & Fit

This is the left lever (rear brake in Australian drop-bar convention) combined with the rear brake caliper. Compatible with Shimano Ultegra R8100 and Dura-Ace R9200 Di2 groupsets. Works with FD-R9250, FD-R8150 front derailleurs and RD-R9250, RD-R8150 rear derailleurs. The BR-R8170 caliper is flat-mount and accepts 140 mm or 160 mm rotors. Compatible brake hoses: SM-BH90-JK-SSR (not included). Uses Shimano mineral oil — do not use DOT fluid. Compatible brake pads: L04C, L03A (resin). Rotor and hose sold separately.