The Shimano 105 Di2 left lever and rear disc brake set brings electronic shifting and powerful hydraulic braking to road riders who demand precision without the Dura-Ace or Ultegra price tag. This pre-bled J-kit includes the ST-R7170 left STI lever paired with the BR-R7170 flat mount rear calliper and a 1700mm pre-bled SM-BH90 hose — everything you need for the left/rear brake circuit, ready to install.

Highlights

• Di2 electronic shifting: Semi-wireless 2x12-speed Di2 system delivers crisp, precise front derailleur actuation from the left lever blade.
• Hydraulic disc braking: Mineral oil hydraulic system provides consistent, powerful stopping with excellent modulation in all weather conditions.
• Pre-bled J-kit convenience: Lever, calliper, and 1700mm hose arrive factory-bled — no bleeding required out of the box, saving workshop time on a new build.
• Reach adjust: Lever blade reach can be dialled in to suit different hand sizes and riding preferences without tools.
• 22mm ceramic pistons: Dual ceramic pistons in the BR-R7170 calliper deliver strong, progressive braking power with minimal fade.
• ICE Technologies compatibility: Designed to pair with Shimano ICE Technologies rotors for superior heat management on long descents.
• Auto pad adjust: Calliper automatically compensates for pad wear, maintaining consistent lever feel throughout the pad life.
• One-way bleeding: Simplified one-way bleed port on the BR-R7170 makes maintenance cleaner and faster than traditional bleed systems.

ST-R7170 Lever

The ST-R7170 left STI lever combines the brake lever and Di2 electronic shift control into a single ergonomic unit. The carbon composite hood body is shaped with a raised hood peak and extended hood length for improved hand support whether you are riding on the hoods, in the drops, or climbing. Two CR1632 coin-cell batteries power the lever with an estimated 3.5–4 year battery life. Reach adjustment allows the lever blade to be positioned closer to or further from the handlebar to suit the rider's hand size. The lever is compatible with full and semi-synchronised shifting modes via E-TUBE PROJECT software.

BR-R7170 Calliper

The BR-R7170 is Shimano's 105-series flat mount hydraulic disc brake calliper. Dual 22mm ceramic pistons provide confident braking power across varied terrain and conditions. Increased pad-to-rotor clearance reduces the likelihood of rotor rub, while the L05A resin pads with cooling fins help manage heat during sustained braking. The simplified one-way bleed port allows maintenance without removing the calliper from the frame. This set is configured for the rear with a 1700mm pre-bled SM-BH90-JK-SSR hose.

Compatibility & Fit

Part of the Shimano 105 R7100 Di2 groupset. Left lever controls the front derailleur in a 2x12-speed Di2 system — compatible with FD-R7150 front derailleur (Di2). Brake calliper uses flat mount (no adapter included for this rear configuration). Compatible with 140mm and 160mm rotors; adapters required for 160mm on some frame mounts. Brake fluid: Shimano mineral oil only (do not use DOT fluid). Hose length: 1700mm (rear). Resin L05A pads with fins included. Not compatible with mechanical (cable) shifting.