Wilwood Red XRS4R Four-Piston Brake Caliper, 1.12-Inch Bores and 1.10-Inch Rotor Width

This red Wilwood XRS4R caliper uses four equal 1.12-inch stainless pistons in a forged aluminum housing. The X-shaped center bridge and internal fluid passages belong to an individual radial-mount brake component, selected here for a nominal 1.10-inch rotor width. Wilwood Engineering was founded by Bill Wood in 1977 and is based in Camarillo, California. The company designs and manufactures disc brake systems and components, including calipers, brake rotors, master cylinders, valves, fittings and brake lines for motorsport, street-performance and specialized applications.

Technical Details

• Manufacturer part number: 120-17201-RD. Type: Forged XRS4R Radial Mount caliper.
• Piston arrangement: 4 stainless steel pistons; bore specification 1.12/1.12 inches. Effective piston area: 1.98 square inches.
• Rotor channel: 1.10-inch nominal width. Specified width limits: 1.00–1.10 inch; rotor outside diameter: 11.75–14.00 inches.
• Mounting: radial, 5.98-inch centers; orientation: universal. 0.39-inch holes; 1.45-inch mounting height.
• Hydraulic inlet thread: 1/8-27 NPT. Match the fitting thread and sealing arrangement to the brake hose.
• Caliper body: forged aluminum; finish: Red Powder Coat.
• Brake pad shape: 10416. Choose pad dimensions and friction material for the brake system.
• Component: one individual hydraulic brake caliper. Select the mating rotor, pads, mounting hardware and line connection to suit the complete brake assembly.
• Piston dust boots: no.
• Caliper component weight: approximately 5.1 lb.

Fitment & Compatibility

A 5.98-inch mounting pattern does not identify the vehicle on its own. Check bracket offset and pad sweep on an 11.75–14.00-inch rotor, then confirm hydraulic balance against the rest of the system.

PMB Performance has over 20 years of brake-component experience. Send the existing caliper identification, rotor measurements and mounting details for help comparing this configuration.