Wilwood 120-17204-BK Forged XRS4R Radial Mount 4-Piston Caliper 1.38 In x .950 In Rotor Black

The Wilwood Forged XRS4R Radial Mount 4-Piston Caliper (120-17204-BK) delivers race-proven stopping power in a lightweight, high-strength forged aluminum body finished in durable black powder coat. Engineered as part of Wilwood's XRS (Next Evolution Street) caliper line, the XRS4R is purpose-built for demanding street performance and track-day applications where consistent, fade-resistant braking is essential.

This caliper features a radial (axial) mount design that provides a more rigid, direct connection to the upright or spindle compared to traditional lug-mount calipers, reducing flex and improving pedal feel. The four-piston configuration uses dual opposing pistons on each side for even pad wear and uniform clamping force across the rotor face. It is sized for a 1.38-inch piston bore and compatible with rotors up to .950 inches wide.

Key Features:

• Forged aluminum caliper body for maximum strength-to-weight ratio
• Radial (axial) mount design for increased rigidity and improved pedal response
• Four-piston opposed configuration for even pad contact and consistent clamping force
• 1.38 in piston bore x .950 in rotor width compatibility
• High-temperature seals for reliable performance under extended heat cycles
• Stainless steel pistons for corrosion resistance and long service life
• Black powder coat finish for a clean, aggressive appearance
• Designed for seamless integration with Wilwood XRS rotor and bracket systems

The Wilwood 120-17204-BK is an ideal upgrade for enthusiasts building a high-performance street or motorsport brake system. Its forged construction and race-derived geometry make it a direct step up from stock OEM calipers, offering superior thermal capacity, reduced unsprung weight, and the consistent feel demanded by performance drivers.