Wilwood 120-11782-Y FNSL4R Forged Narrow Superlite 4R Radial Mount Disc Brake Caliper - Yellow

The Wilwood 120-11782-Y FNSL4R Forged Narrow Superlite 4R is a high-performance, radial-mount 4-piston disc brake caliper finished in Yellow anodize. Featuring dual 1.12" piston bores and designed for use with a 1.10" disc, this caliper is engineered for competition and high-performance street driving applications. Radial mounting provides two planes of adjustment for precise alignment over the rotor, simplifying adaptation across a wide range of vehicle builds.

Stress-Flow Forged Aluminum Construction:

Starting at just 4.9 lbs, the FNSL4R body is the result of computer-generated solid modeling and FEA stress analysis. Each caliper body is stress-flow forged from premium-grade aluminum alloy billets — a process that re-aligns the metal's internal grain structure to follow the contour of the caliper body. This eliminates the structural interruptions caused by traditional billet machining, resulting in the strongest possible aluminum caliper body.

Key Features:

• Radial mounting with two planes of adjustment for accurate disc alignment
• Stress-flow forged premium aluminum alloy body — lightweight at 4.9 lbs starting weight
• 1.12" / 1.12" dual piston bores for balanced braking force; compatible with 1.10" disc thickness
• One-piece stainless steel pistons standard — chosen for low heat transfer and corrosion resistance
• Upgradeable to Wilwood's Thermlock pistons for enhanced thermal barrier performance
• SRS bridge plates eliminate bridge wear from pad gouging and extend caliper service life
• Spring-loaded SRS plate action eliminates pad rattle and dampens harmonic vibrations that cause brake squeal
• Dual end bleed screws with internal fluid crossovers protect against track debris damage
• High-temperature, square-face bore seals maximize sealing area and provide controlled piston retraction on release
• Compatible with the full range of Wilwood brake pad compounds for any competition or performance driving application
• Yellow anodized finish for high-visibility, corrosion-resistant appearance
• Usable as a front or rear caliper

The FNSL4R's Thermlock piston upgrade option creates a multi-layer thermal barrier that significantly reduces heat transfer from the brake pads into the caliper body, seals, and fluid — translating to longer component life and reduced risk of heat-induced brake fade under sustained hard use.