Wilwood Right FSLI4-ST Caliper, 0.81-Inch Rotor Width / 1.88/1.75-Inch Thermlock Pistons

This right-hand Forged Superlite Internal 4 ST combines unequal 1.88/1.75-inch bores with Thermlock pistons. The insulated piston construction limits heat transfer into the fluid and seals, and internal passages carry fluid between the two caliper halves. With a range spanning calipers, brake rotors, master cylinders, valves, fittings and brake lines, Wilwood Engineering designs and manufactures complete disc braking systems and their components. Bill Wood founded the Camarillo, California-based company in 1977 for a market now covering motorsport, street-performance and specialized applications.

Technical Details

• Manufacturer part number: 120-13155. Component: Forged Superlite Internal 4 ST caliper.
• Supply: one brake caliper, not a complete axle brake kit. Match the mating rotor, pads, bracket and connection hardware to the installation.
• Rotor compatibility: nominal width 0.81 inch; diameter 11.75–13.06 inches. Specified rotor-width limits: 0.75–0.84 inch.
• Hydraulic inlet thread: 1/8-27 NPT. Use a fitting with the correct thread and sealing seat.
• Caliper weight: approximately 5.2 lb.
• Pistons: 4 Thermlock; bore specification: 1.88/1.75 inches. Effective piston area: 5.18 sq in.
• Mounting: lug, 3.50-inch centers; right hand orientation. Mount holes: 0.45 inch; height: 2.85 inches.
• Compatible brake pad shape: 7420; choose the required compound for the brake system.
• Body: forged aluminum; finish: Type III anodize.
• Piston dust boots: not fitted.

Fitment & Compatibility

Use the 3.50-inch lug centers and 2.85-inch mount height to compare the attachment geometry. Check an 11.75–13.06-inch rotor diameter, 0.81-inch nominal width and type 7420 pad cavity before adapting it to a brake assembly.

PMB Performance brings more than 20 years of experience to brake-part selection. Include the existing caliper, rotor and mounting details when requesting help with this assembly.