Wilwood Thermlock FNSL4R Caliper, 1.25-Inch Pistons / 1.10-Inch Rotor Width / Type III

This anodized FNSL4R-ST uses four 1.25-inch Thermlock pistons and a nominal 1.10-inch rotor-width channel. The effective piston area is 2.46 square inches. 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: 120-12602. Component: Forged Narrow Superlite 4 Radial Mount caliper.
• Supply: one brake caliper, not a complete axle brake kit. Match the mating rotor, pads, bracket and connection hardware to the installation.
• 4 Thermlock pistons with 1.25-inch bore diameter. The specified effective area is 2.46 sq in.
• Hydraulic inlet thread: 1/8-27 NPT. Use a fitting with the correct thread and sealing seat.
• 5.98-inch radial mounting pattern, universal; mounting height 1.45 inches and hole size 0.39 inch.
• Type III anodize finish on a forged aluminum caliper body.
• Caliper weight: approximately 5.0 lb.
• Piston dust boots: not fitted.
• Brake pad profile 7416; select friction material for the actual operating conditions.
• The rotor channel is specified for 1.10-inch nominal width. Rotor outside diameter: 11.75 to 14.00 inches. Specified rotor-width limits: 1.00–1.10 inch.

Fitment & Compatibility

Verify the Thermlock piston construction and 7416 pad sweep when matching a replacement. The 5.98-inch radial bracket must locate the rotor correctly; this is the 1.25-inch-bore caliper, not the 1.12-inch-bore version.

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.