Shimano Ultegra BR-R8170 Hydraulic Disc Brake Caliper - Rear, Flat Mount

Ultegra Stopping Power for Your Rear Flat Mount

The BR-R8170 is the rear caliper from Shimano's 12-speed Ultegra R8100 group, and it's the one we reach for when a road bike needs a fresh rear brake that matches the rest of an Ultegra build. It's a 2-piston, flat-mount hydraulic caliper running Shimano mineral oil, designed to pair with the Ultegra ST-R8170 Di2 shift/brake levers. Paired with those levers, you get the quick initial bite and smooth, controllable modulation the R8100 brakes are known for, so you can feather your speed into a tight corner or haul it down hard on a wet descent.

Shimano gave this generation 10% more pad clearance, which means less rotor rub and a noticeably quieter brake, even after a long, hot descent. It's also easier to work on. The one-way bleed design has a separate bleed port, so you can bleed the brake without taking the caliper off the frame. The caliper works with Shimano's ICE TECHNOLOGIES finned pads and rotors (RT-MT800 or RT-CL800 recommended) to manage heat and keep braking consistent. It's set up for 140 or 160mm rotors and comes with finned resin pads and 25mm rear mounting bolts.

Please note that this is the rear caliper only. The brake lever, hose and rotor are sold separately.

Whether you're replacing a worn or corroded rear caliper, finishing an Ultegra R8100 Di2 build, or upgrading the rear brake on your endurance or race bike, the BR-R8170 delivers quiet, consistent Ultegra-level braking.

Shimano was founded in 1921 by Shozaburo Shimano in Sakai, Japan, and the company is still based there today. More than a century later, it's one of the biggest names in cycling components. Ultegra sits just below Dura-Ace in Shimano's road lineup and brings much of that race-level performance to riders who log serious miles.