Wilwood 120-12602 FNSL4R Forged Billet Rear Disc Brake Caliper

The Wilwood FNSL4R/ST forged billet disc brake caliper delivers championship-proven performance for demanding racing and high-performance street applications. Featuring four Thermlock® pistons, this rear caliper is specifically designed to provide matched rear braking bias when paired with Aero6/ST or other larger piston front calipers.

Advanced Forged Construction:

Weighing just 4.9 pounds, the FNSL4R caliper body is stress-flow forged from premium grade aluminum alloy billets using computer-generated solid modeling and FEA stress analysis technology. The stress-flow forging process re-aligns the metal's internal grain structure to flow within the contour of the caliper body, eliminating the stresses and grain interruptions that occur when machining straight block billets. This manufacturing method produces an exceptionally strong and durable caliper body that outperforms conventionally machined alternatives.

Thermlock® Piston Technology:

Each caliper is equipped with Wilwood's exclusive Thermlock pistons, which feature a multi-part design that creates a highly efficient thermal barrier. This advanced piston construction significantly reduces heat transfer from the brake pads to the caliper body, seals, and brake fluid. The result is cooler operating temperatures, extended component service life, and reduced risk of heat-induced brake fade.

Key Features:

• Stress-flow forged aluminum alloy body for maximum strength and durability
• Four Thermlock® pistons with advanced thermal barrier technology
• Available in multiple piston bore sizes for front or rear brake applications
• SRS bridge plates eliminate pad gouging and extend caliper service life
• Spring-loaded SRS plates eliminate pad rattle and reduce brake squeal
• Two-piece bleed screws on each end for reliable brake bleeding
• Internal fluid crossovers protect against track debris damage
• High-temperature square-faced bore seals provide maximum sealing area
• Controlled piston retraction on brake release
• Compatible with full range of Wilwood brake pad compounds
• Lightweight design at 4.9 pounds

The FNSL4R caliper's combination of advanced materials, precision engineering, and race-proven design makes it an ideal choice for serious motorsports competitors and performance enthusiasts seeking superior braking performance and reliability.