Wilwood Right Rear HM4 Hydra-Mechanical Caliper, 1.00-Inch Piston / 0.19-Inch Rotor Width

The right-hand HM4 is a hydra-mechanical rear caliper for a properly matched utility-vehicle brake system. Its clear-anodized cast aluminum body houses one 1.00-inch stainless piston and works over a nominal 0.19-inch rotor width. Founded in 1977 by Bill Wood, Camarillo, California-based Wilwood Engineering designs and manufactures disc braking systems. Its motorsport, street-performance and specialized range covers calipers, brake rotors, master cylinders, valves, fittings and brake lines, selected as parts of a complete system.

Technical Details

• Manufacturer part number: 120-11025. Component: HM4 Hydra-Mechanical caliper.
• Supply: one brake caliper, not a complete axle brake kit. Match the mating rotor, pads, bracket and connection hardware to the installation.
• Brake pad profile 6407; select friction material for the actual operating conditions.
• 3.00-inch floating mounting pattern, right hand; hole size 0.67 inch.
• clear anodize finish on a cast aluminum caliper body.
• Caliper weight: approximately 2.7 lb.
• 1 stainless steel piston with 1.00-inch bore diameter. The specified effective area is 0.79 sq in.
• Piston dust boots: included.
• The rotor channel is specified for 0.19-inch nominal width. Rotor outside diameter: 6.00 to 11.20 inches. Specified rotor-width limits: 0.15–0.19 inch.
• Hydraulic inlet thread: M10 x 1.00. Use a fitting with the correct thread and sealing seat.

Fitment & Compatibility

Check the floating bracket's 3.00-inch centers, mechanical linkage and M10 x 1.00 inlet. A utility-vehicle application must be confirmed by the complete mounting and actuation dimensions rather than the HM series name alone.

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