AP Racing J Hook Competition Brake Disc/Rotor Replacement Ring. Does not include rotor hat or hardware/bobbins. Save costs by replacing the friction ring instead of the whole rotor assembly.
(325x32mm / 12.81"x1.25")
Vehicle Side: Left
Weight: 14.93 lbs
Cooling Vanes: 70
AP Racing P/N: CP3870-139GC
*Torque specs for this disc and hardware assembly: 124 lb-in*
AP Racing J Hook discs were developed for endurance racing. Proven through various sports car series throughout the USA including ALMS, Rolex, Grand Am, and more.
Superior cooling and airflow over OEM discs. The internal directional vanes have a shape that is optimized to help promote smooth airflow. Please note that rotors are designed for the left and right sides of the vehicle and must be installed accordingly otherwise proper cooling can not be achieved.
AP Racing Discs also have far more internal cooling vanes, which promote heat transfer and airspeed through the disc. Compared to OEM discs, where oftentimes there may only be 48 vanes, 60+ vane discs are less prone to coning, distortion, and cracking, while providing less brake fade, reduced judder, more even pad contact, and longer service life.
The proprietary J Hook Slot pattern reduces cool spots across the disc often seen with straight slotted discs. Slotted discs also improve brake pad bite/torque and feel over OEM smooth-plain faced discs. Slotted rotors also significantly reduce the potential for the rotors to crack under stress, as cross-drilled rotors create mini stress risers and uneven cooling, which weakens the rotors.
The J Hook design takes it a step further over traditional straight slotted rotors, ensuring the cooling across the rotor is even more uniform, improving the performance of the rotors and increasing their overall life.
J Hook discs also mount up to a floating hat assembly which further improves brake cooling and allows the friction ring to expand independent from the hat, eliminating distortion.