Wilwood 120-16683 Forged Narrow Superlite Radial Mount Disc Brake Caliper - FNSL4R 4R

The Wilwood Forged Narrow Superlite 4R (FNSL4R) is a high-performance 4-piston disc brake caliper engineered for extreme braking demands across a broad range of competition and sports driving applications. The radial mounting design simplifies adaptation and offers two planes of adjustment for precise disc alignment, making installation and setup straightforward even in complex brake configurations.

At the heart of the FNSL4R's performance advantage is its stress-flow forged aluminum alloy body. Each caliper body is forged from premium-grade aluminum billets, a process that re-aligns the metal's internal grain structure to follow the contour of the caliper body — eliminating the stress points and grain interruptions that result from traditional billet machining. The result is one of the strongest, most durable aluminum caliper bodies available, starting at just 4.9 lbs, optimized through computer-aided solid modeling and FEA (Finite Element Analysis) stress analysis.

Key Features:

• Radial mount design — provides two planes of alignment adjustment over the rotor for precise fitment
• Stress-flow forged aluminum body — premium-grade alloy construction for maximum strength with minimal weight
• 4-piston configuration — delivers consistent, powerful clamping force across the brake pad surface
• One-piece stainless steel pistons (standard) — selected for low heat transfer and superior corrosion resistance
• Thermlock piston upgrade available — multi-part piston design creates a thermal barrier to reduce heat transfer to the caliper body, seals, and brake fluid, minimizing heat-induced pedal fade
• SRS (Stainless Rotor Saver) bridge plates — eliminate bridge wear from pad gouging, reduce pad rattle, and dampen harmonic vibrations that contribute to brake squeal
• Dual two-piece bleed screws — one on each end with internal fluid crossovers, protected from track debris and physical damage
• High-temperature square-faced bore seals — maximize sealing area and provide controlled piston retraction upon brake release
• Universal right/left hand mount — usable as either a front or rear caliper
• Compatible with the full range of Wilwood brake pad compounds for street, autocross, road racing, and other performance applications

The FNSL4R is engineered to deliver big stopping power in a compact, lightweight package. Whether used on the track or street, this caliper is built to withstand extreme heat cycles and demanding environments while maintaining consistent, fade-resistant braking performance.