Wilwood XRS4R Anodized Four-Piston Caliper for 0.95-Inch-Wide Brake Rotors

This anodized Wilwood XRS4R is built around a nominal 0.95-inch rotor-width channel. The four 1.38-inch bores, internal fluid passages and forged X-bridge body make it a distinct intermediate-width configuration within the radial-mount range. 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: 120-17204. Type: Forged XRS4R Radial Mount caliper.
• Bore sequence 1.38/1.38 inches across 4 pistons. Piston construction: stainless steel; specified effective area 3.00 square inches.
• Rotor dimensions: outside diameter 11.75–14.00 inches; nominal width 0.95 inch, with width limits of 0.89–0.99 inch.
• Attachment geometry: radial mount with 5.98-inch centers; 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.
• Construction and surface: forged aluminum, finished in Type III Anodize.
• Pad fit uses shape 10416. Match the pad to the rotor and intended operating conditions.
• 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 5.0 lb.

Fitment & Compatibility

Confirm a rotor between 0.89 and 0.99 inch wide, then check hat offset and the 11.75–14.00-inch diameter envelope. Pad alignment and wheel clearance still depend on the bracket used.

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.