Shimano Dura-Ace Di2 BR-RS9170 Flat Mount Hydraulic Disc Brake

The Shimano Dura-Ace BR-RS9170 Flat Mount Hydraulic Disc Brake is Shimano's flagship road disc caliper — smaller and lighter than its predecessors, yet engineered to shed heat faster and stop harder. The dual-piston design has been refined for a sharper balance of braking power and modulation, with pistons that self-adjust and retreat farther from the rotor to prevent rub caused by minor frame flex or imperfect wheel seating.

The lower-profile caliper sits tighter behind the fork and stays, reducing its wind footprint without compromising feel. Chamfered pad edges guide rotors in cleanly, and the gravity-bleed system makes maintenance straightforward — open the valve and the fluid does the work. These calipers mount via Shimano's flat mount standard and are sold individually; specify front or rear at checkout. Hydraulic hose and fluid are not included with the caliper alone — if you purchase compatible levers separately, hose and fluid are typically included with those. Rotors are sold separately; Shimano's SM-RT900 is the recommended pairing, available in 140mm and 160mm.

Shimano Dura-Ace BR-RS9170 Specs at a Glance

• Mount standard: Flat mount
• Piston configuration: Two-piston hydraulic
• Weight: Approx. 256g per caliper (515g per pair)
• Rotor compatibility: 140mm or 160mm (sold separately)
• Available as: Front or Rear (sold individually)