AP Racing by Essex Rear Radi-CAL Brake Kit for Porsche 991.2 GT3 Cup - 380mm J-Hook

The AP Racing by Essex Radi-CAL Competition Brake Kit (Rear) is an elite-level braking solution specifically designed for the Porsche 911 GT3 Cup (991.2). This kit replaces the factory rear brakes with a system engineered for the extreme thermal loads of professional motorsport, offering superior cooling, weight savings, and consistent pedal feel.

Motorsport-Grade Performance

At the core of this kit is the AP Racing CP9449 Radi-CAL four-piston caliper. The Radi-CAL design is a major departure from traditional symmetric calipers; its asymmetrical shape is computationally optimized to be stiffer and lighter while improving airflow. This results in significantly less caliper "flex" under high pressure, providing the driver with more precise modulation and a firmer pedal.

Advanced Thermal Management

The kit utilizes 380mm x 28mm AP Racing J-Hook rotors. These heavy-duty racing discs feature a high vane count for rapid heat dissipation and the proprietary J-Hook groove pattern, which provides a clean pad surface and better "bite" without the cracking risks associated with traditional drilled rotors. The floating mounting system allows the disc to expand and contract freely under extreme heat, preventing coning and vibration.

Key Performance Features

• Radi-CAL Design: Asymmetrical caliper body increases stiffness and reduces weight for better unsprung mass.

• J-Hook Racing Rotors: 380mm discs provide massive thermal capacity and superior pad outgassing.

• Ventilated Stainless Steel Pistons: Reduces heat transfer from the pads to the brake fluid, preventing pedal fade during long stints.

• Fully Rebuildable: Calipers feature high-temperature seals and are designed for easy servicing in a racing environment.

• Weight Reduction: Significant weight savings over OEM components, improving suspension response and overall agility.

This part also goes by the following cross reference.

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