Wilwood Left HM4 Rear Hydraulic / Mechanical Brake Caliper, Clear Finish

This left-hand HM4 caliper combines a hydraulic piston with mechanical brake actuation in a cast aluminum floating assembly. The 1.00-inch bore and nominal 0.19-inch rotor-width channel define this utility-oriented rear version. Bill Wood established Wilwood Engineering in 1977. Based in Camarillo, California, the company designs and manufactures disc brake systems, from calipers and brake rotors to master cylinders, valves, fittings and brake lines for motorsport, street-performance and specialized use.

Technical Details

• Manufacturer part number: 120-11026. 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.
• Construction and surface: cast aluminum housing finished in clear anodize.
• Bore configuration 1.00 inches across 1 piston; piston material: stainless steel. Hydraulic effective area: 0.79 square inches.
• Pad fit is type 6407. Match the pad dimensions and compound to the rotor and intended braking conditions.
• Caliper weight: approximately 2.7 lb.
• Piston dust boots: included.
• Bracket interface: 3.00-inch floating centers with 0.67-inch holes; orientation: left hand.
• Nominal rotor width 0.19 inch; compatible outside diameter from 6.00 through 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

Verify the left-hand actuator clearance and complete release of the mechanism. The bracket needs 3.00-inch mounting centers, and rotor diameter must remain within the specified 6.00–11.20-inch envelope.

With 20+ years of experience, PMB Performance can help compare the actual brake hardware. Supply the caliper number, rotor dimensions and mounting measurements when asking about compatibility.