Wilwood Yellow XRS4R Radial Caliper, 0.95-Inch Rotor Width and Four 1.38-Inch Bores

This yellow Wilwood XRS4R is a hydraulic brake caliper for a nominal 0.95-inch-wide rotor. Its stainless piston arrangement is equal-bore, while the forged housing retains the open center bridge and internal passages characteristic of the XRS range. Bill Wood established Wilwood Engineering in 1977. Based in Camarillo, California, the company designs and manufactures disc brake systems for motorsport, street-performance and specialized use, including calipers, brake rotors, master cylinders, valves, fittings and brake lines.

Technical Details

• Manufacturer part number: 120-17204-Y. Type: Forged XRS4R Radial Mount caliper.
• Attachment geometry: radial mount with 5.98-inch centers; universal. 0.39-inch holes; 1.45-inch mounting height.
• Rotor dimensions: outside diameter 11.75–14.00 inches; nominal width 0.95 inch, with width limits of 0.89–0.99 inch.
• Pad fit uses shape 10416. Match the pad to the rotor and intended operating conditions.
• Bore sequence 1.38/1.38 inches across 4 pistons. Piston construction: stainless steel; specified effective area 3.00 square inches.
• 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 Yellow Powder Coat.
• Caliper component weight: approximately 5.0 lb.
• 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.

Fitment & Compatibility

Bracket offset and rotor diameter determine whether the pad follows the correct friction track. Use the listed width limits and mounting measurements together, without assuming a direct vehicle application from the finish or family name.

For help matching this caliper, contact PMB Performance with the brake-package details and rotor measurements. Our team has more than 20 years of experience with brake parts and fitment.