Wilwood Anodized XRS4R Caliper, 0.81-Inch Rotor Width and 1.38-Inch Stainless Pistons

The nominal 0.81-inch rotor channel distinguishes this anodized Wilwood XRS4R from wider versions of the same caliper. Four 1.38-inch stainless pistons operate in a forged housing, with internal fluid routing and radial mounting for a separately engineered brake package. 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: 120-17203. Type: Forged XRS4R Radial Mount caliper.
• 4-piston hydraulic layout with 1.38/1.38-inch bores and 3.00 sq in of effective area; piston type: stainless steel.
• Hydraulic inlet thread: 1/8-27 NPT. Match the fitting thread and sealing arrangement to the brake hose.
• 5.98-inch-center radial attachment, universal orientation. 0.39-inch holes; 1.45-inch mounting height.
• Type III Anodize finish on a forged aluminum body.
• Nominal rotor width 0.81 inch; compatible width range 0.75–0.84 inch. Rotor diameter specification: 11.75–14.00 inches.
• Caliper component weight: approximately 4.9 lb.
• Compatible pad profile 10416; confirm thickness and compound for the installation.
• Piston dust boots: no.
• Component: one individual hydraulic brake caliper. Select the mating rotor, pads, mounting hardware and line connection to suit the complete brake assembly.

Fitment & Compatibility

Use the 0.75–0.84-inch specified width limits to check the rotor rather than substituting a wider XRS variant. Confirm pad sweep, bracket height and clearance to the inner wheel barrel before installation.

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.