Width and Thermal Mass:

One of the primary goals with a brake disc is to put the mass of the disc where it counts. The area of the disc that is swept by the pads is where the most heat will enter the disc, and that area's design is critical in determining how heat will flow through and out of the disc. With the OEM discs, much of the disc's mass is located in the hat portion, near the hub of the car. Having a mass of hot iron in that area isn't particularly beneficial to lowering brake temps, and also adds wear and tear on your wheel bearings, etc. With an aftermarket two-piece disc, almost all of the disc's mass is located in the swept region, which is where it can absorb and radiate heat through the disc's vanes. Therefore, two discs of roughly the same overall dimensions on paper can have tremendously different capabilities to absorb and transfer brake energy into heat.

The CP3862 is 299mm x 32mm. By using a small diameter disc that is wider, we can gain the thermal mass we need without requiring large diameter wheels. We go from an OEM 24mm wide disc to a 32mm disc. We now have a beautiful wide air gap to flow a ton of air. We also maintain a lower moment of inertia. Essentially what that means is, a smaller diameter disc has its weight distributed more closely to the center axis around which it spins(hub), and is easier to accelerate than a larger diameter disc of equal mass.



OEM BRZ disc vs. AP Racing CP3862 Weight:

The weight difference between the AP Racing CP3862 and the OEM front disc is glaring. The CP3862 weighs in at svelte 12.2 lbs. with hat, while the OEM front disc is a portly 17 lbs., a difference of roughly 5 lbs. unsprung weight (a hat is not attached to the AP disc below, which adds roughly 1lb.)!

Vanes:

The discs we chose for our Sprint system have 60 directional vanes. As mentioned above, the wide air gap will flow a large volume of air, and the high vane count will provide a large heat sink. The increased directional vane count amplifies air speed through the disc, reduces air recirculation between vents, and also increases convective heat transfer and heat distribution. In other words, both air and heat move more quickly and evenly through the disc, creating increased stability under the extreme loads of racetrack use. The disc is less prone to coning, distortion, and cracking, while providing cooler running temperatures, less brake fade, reduced judder, and a longer service life.

J Hook Slot Design:

When you cut a slot or drill a hole in a disc you impact heat transfer. The area around the slot or hole acts as a cool spot when the disc heats up, which is not ideal. Ideally, heat is distributed uniformly around the disc so it can be hit with the cooling air that is pumping through the disc, radiate outwards away from the disc, etc. Cool spots create stress risers and increase the likelihood of the disc cracking. They also cause the face of the disc to distort unevenly, leading to uneven pad deposits, vibration, and judder. During exhaustive R&D testing, AP's J Hook design was found to create a constant pathway of evenly distorted material on the face of the disc. The hooks are spaced out as evenly as possible both around the circumference of the disc, as well as from the inside edge (where the hat attaches) to outer edge, with a slight overlap to promote even heat distribution/distortion. In addition to reducing cracking, the even heating of the disc also helps provide an even transfer layer of pad material on the disc when you bed them in.

Additionally, the J Hook slot pattern produces a greater number of leading edges for the pads to bite into vs. a traditional curved slot pattern. While this may lead to slightly more whirring or scraping noises from the discs when applying the brakes, the benefits of more even heat distribution, less propensity to crack, cleaner pad material transfer during bed-in, and more bite far outweigh any potential increase in NVH for the serious enthusiast.

Metallurgy:

AP Racing has been designing brake components for more than 50 years. They've had their components on cars that have won more than 600 grand prix's (Formula 1). On any given race weekend, AP J Hook discs can be found on 75% or more of the NASCAR Sprint Cup grid. AP has learned from these experiences, and have developed a proprietary iron alloy with extreme durability, designed specifically for what you intend to do with it (flog the hell out of it)

Price
One of the best aspects of the AP Racing CP3862 disc is that it is extremely inexpensive. The CP3862 iron replacement discs retail at only $158 each! Heavy, crack-prone OEM one-piece discs will likely cost 2/3 of that, and that won't have any of the benefits or last nearly as long. Due to how stout these discs are, our customers won't be replacing them very often, but when they do it will be very easy on the wallet.

Summary of Features and Benefits
Our Sprint Brake System will offer a wide array of benefits, while shaving roughly 8 lbs. of unsprung weight per corner on the FR-S/BRZ! With a retail price of approximately $2,099, it's going to be very tough finding another modification to the car that will offer more benefits per dollar.

Approximately 10 lbs. unsprung weight reduction from both front corners of the car. Incredible array of inexpensive brake pad options. These pads are far larger/thicker than stock, and will last a very long time on the FT86. You'll replace your pads a lot less often, saving money in the long-term
Mitigation of pad knockback due to 4lb. anti-knockback springs in the calipers
Caliper finish that is highly resistant to wear and deterioration under high heat track conditions
Stainless steel caliper hardware for a long caliper service life under frequent pad change conditions
High temperature, low drag seals that will hold up to track temps better than OEM components= less rebuilding and longer service life
No dust boots to burn up and make a big mess
Simple pad change with one bolt and no spring clips (no tapping out the pins as you would on an STI Brembo)
Extremely compact package for superior wheel fitment
Stainless steel pistons that keep heat out of your brake fluid to resist fluid fade during extended track sessions
Lifetime professional caliper rebuilding support by Essex (at a fee)- pull off your calipers, send them to us, we clean, inspect, and rebuild and return them
High airflow, heavy duty AP Racing J Hook brake discs that weigh 5 lbs. less than the OEM units despite their larger size, available at an extremely competitive replacement price ($158 each).
AP Racing J Hook slot design that gives more pad bite/feel, and distributes heat evenly throughout the disc
Disc metallurgy specifically designed to handle the temps typically seen on track offers a long service life
Highest quality, Spiegler stainless steel brake line with clear sheath that reduces compliance over OEM rubber design.
Much more attractive appearance vs. OEM FT86 brakes
Saves your OEM components in good condition, so you can reinstall them when you sell your car
Because of their quality and trusted brand name, AP Racing brake systems hold their value well in the used market, and you will get a considerable amount of money back out of them when you decide to part and sell your car

Available for the following vehicles:
• Scion FR-S, Subaru BRZ, Toyota 86