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 at every speed and in every condition.

Highlights

• Wireless Di2 electronic shifting with 2x12-speed compatibility — no cables between shifters
• Servo Wave hydraulic disc braking for progressive, predictable power throughout the lever stroke
• Flat-mount BR-R8170 rear caliper with 10% wider pad spacing for quieter, cleaner braking
• Reach adjust mechanism with up to 16.4 mm of adjustment for a perfect lever-to-grip fit
• One-Way Bleeding system for quick, mess-free servicing
• CR1632 coin-cell battery with up to 1.5–2 years of life between changes
• Customisable shift modes (Manual, Full Synchro-Shift, Semi Synchro-Shift) via the E-Tube Project app

Lever Design & Ergonomics

The ST-R8170 hood sits taller with a raised peak that curves gently inward, giving your palm a more secure grip on long climbs and technical descents. The carbon-fibre-reinforced polymer hood body keeps weight minimal while the aluminium brake lever provides a solid, direct feel under hard braking. Reach adjust lets you dial in lever position to suit any hand size without tools.

Braking Performance

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

Compatibility & Fit

This kit is the left lever (rear brake in Australian/standard drop-bar setup) combined with the rear brake caliper. Compatible with Shimano Ultegra R8100 and Dura-Ace R9200 Di2 groupsets. Front derailleurs: FD-R9250, FD-R8150. Rear derailleurs: RD-R9250, RD-R8150. Brake hoses: SM-BH90-J-SSR, SM-BH90-JK-SSR (not included). Caliper is flat-mount and accepts a 160 mm rotor. Mineral oil hydraulic fluid — do not use DOT fluid. Rotor and hose sold separately.