Rotor rub and squeal are the two complaints that follow disc brakes around on gravel bikes, and both usually trace back to tight pad clearance getting exaggerated by frame flex under load. The Shimano GRX BR-RX820 caliper addresses that directly with 10 percent more pad clearance than the previous GRX generation, which gives the rotor more room to move without contacting the pads during hard efforts or when a loaded bike torques the rear triangle. It's a small change on paper that pays off every time you stand on the pedals with a full frame bag.

This is the 2-piston flat-mount hydraulic caliper that anchors the 12-speed GRX RX820 groupset. The body is aluminum with resin pistons and a straight hose fitting, and it ships with L05A finned resin pads that use Shimano's Ice Technologies aluminum cooling fins to shed heat on long descents. Rotor compatibility runs from 140mm to 180mm, so you can spec it aggressively for loaded bikepacking or keep it light for dry-weather day rides.

Compatibility reaches well beyond the GRX ecosystem, which matters if you're mixing groupsets or upgrading piecemeal. The BR-RX820 pairs with every current Shimano hydraulic road and gravel lever we've checked—Dura-Ace ST-R9270, Ultegra ST-R8170, 105 ST-R7120 and ST-R7170, GRX ST-RX820 and ST-RX610, plus the older ST-R9120, R8020, R7020, RX810, and Tiagra ST-4720 levers. If you're rebuilding an older gravel bike and want current-generation braking without swapping shifters, this caliper drops in cleanly.... Read More