Wilwood – Forged Superlite 4 Radial Mount Brake Caliper (FSL4R / FSL4R-ST)

Wilwood – Forged Superlite 4 Radial Mount Brake Caliper (FSL4R / FSL4R-ST)

The Wilwood Forged Superlite 4 Radial Mount Brake Caliper (FSL4R) is engineered for sustained high-temperature braking across dirt and asphalt ovals, road course, rally, and off-road applications. Featuring differential bore pistons, the FSL4R compensates for leading-edge mechanical loading and temperature differences across the pad face, significantly reducing pad taper wear during long green-flag runs.

ST models are equipped with Thermlock® pistons, which block heat transfer from the pads and reduce temperatures in the caliper, fluid, and seals by up to 25% compared to standard stainless steel pistons—making them ideal for extreme braking environments.

The FSL4R design eliminates external fluid cross-over tubes by using internal fluid ports, replacing the transfer tube with dual bleed screw assemblies. This allows the caliper to be used in left-hand or right-hand configurations without requiring leading or trailing orientation.

With an assembled weight of just 4.4 lbs, the FSL4R combines exceptional strength and reduced mass thanks to its stress-flow forged aluminum construction, computer-modeled geometry, and closed-end bridge design that resists deflection under load.

Features & Benefits

• Differential bore pistons – Reduces pad taper wear in sustained high-heat use
• Thermlock® pistons (ST models) – Up to 25% reduction in caliper, fluid, and seal temperatures
• Forged aluminum construction – Superior strength with minimal weight
• Ultra-lightweight design – Approx. 4.4 lbs assembled
• Internal fluid ports – Eliminates external crossover tubes
• Dual bleed screw assemblies – Left or right mounting without leading/trailing setup
• Closed-end bridge design – Increased rigidity and reduced caliper deflection
• Type III hard anodized finish – Wear-resistant aluminum-oxide ceramic coating
• Versatile applications – Dirt, asphalt, road course, rally, and off-road racing

Caliper Details

• Caliper Type: Forged Superlite 4 Radial Mount (FSL4R / FSL4R-ST)
• Mount Style: Radial mount
• Weight: Approx. 4.4 lbs assembled
• Pistons: Differential bore (Thermlock® optional on ST models)
• Finish: Type III hard anodized
• Material: Stress-flow forged premium aluminum alloy