The Wilwood Forged Superlite Internal Radial-Mount Calipers with Thermlock Pistons is the benchmark in asphalt short track, late model, modified and open wheel competition. It also enjoys prominence in a variety of road-race, rally and sport driving applications.
 
Thermlock® pistons in the ST models block heat transfer from the pads and reduce temperatures in the caliper, fluid, and seals by up to 25% over standard stainless steel pistons. Featuring a wear resistant Type III hard anodize finish, these are the go-to calipers for all types sustained hard braking on dirt and asphalt ovals and a wide range of off-road, rally and road course applications.
 
The new FSL4R model series is the latest innovation to this Superlite family of calipers. It has been redesigned with internal fluid ports that eliminate the external fluid cross-over tubes. The transfer tube has been replaced with two additional bleed screw assemblies which allow symmetrical piston bore models to be mounted either right or left in a leading or trailing position. Differential bore models still require left hand and right hand orientation, but no leading or trailing configuration is necessary.The most noteworthy feature of all the FSL4R caliper models is the exceptional strength and reduced weight of the forging. With assembled weights just at 4.4 pounds, the caliper body design in itself is a product of computer generated solid modeling and stress analysis technology. Each caliper features closed end bridges with a radial transition down to the main body and piston bore housings. The elimination of machined steps and sharp shoulders in this critical area provides a measurable increase in overall body strength and resistance to deflection under load. Every FSL4R body is stress-flow forged from a premium grade aluminum alloy billet.
 
Calipers are for 1.25" Rotors.