Wilwood XRS4R Red Radial Brake Caliper, 1.38-Inch Pistons / 1.00–1.10-Inch Rotor-Width Limits

A red powder-coated XRS4R housing carries this Wilwood caliper's four 1.38-inch stainless pistons. With a 1.10-inch nominal rotor width and 5.98-inch radial centers, it is a dimensionally specified component for an engineered brake assembly. From its base in Camarillo, California, Wilwood Engineering designs and manufactures disc brake systems and components. Bill Wood founded the company in 1977; its motorsport, street-performance and specialized range includes calipers, brake rotors, master cylinders, valves, fittings and brake lines.

Technical Details

• Manufacturer part number: 120-17205-RD. Type: Forged XRS4R Radial Mount caliper.
• Construction and surface: forged aluminum, finished in Red Powder Coat.
• Bore sequence 1.38/1.38 inches across 4 pistons. Piston construction: stainless steel; specified effective area 3.00 square inches.
• Attachment geometry: radial mount with 5.98-inch centers; universal. 0.39-inch holes; 1.45-inch mounting height.
• Component: one individual hydraulic brake caliper. Select the mating rotor, pads, mounting hardware and line connection to suit the complete brake assembly.
• Rotor dimensions: outside diameter 11.75–14.00 inches; nominal width 1.10 inch, with width limits of 1.00–1.10 inch.
• Pad fit uses shape 10416. Match the pad to the rotor and intended operating conditions.
• Caliper component weight: approximately 5.1 lb.
• Hydraulic inlet thread: 1/8-27 NPT. Match the fitting thread and sealing arrangement to the brake hose.
• Piston dust boots: no.

Fitment & Compatibility

Compare the 3.00-square-inch piston area with the existing hydraulic design before changing caliper size. The rotor's width and diameter, bracket offset and bleed-screw orientation must all suit the installation.

PMB Performance brings over 20 years of experience to brake-component selection. Share the installed caliper, rotor size and mounting arrangement so the relevant dimensions can be compared.