AP Racing's Heavy Duty J Hook Racing Discs were specifically designed to handle racetrack abuse.  These are the same discs used on the fastest cars at the elite level of motorsports, including ALMS, NASCAR Sprint Cup, etc.  They provide increased cooling, less judder, fewer cracks, and an increased service life vs. competing discs.  When you run an AP disc, you can be confident that you're using the best parts available at any price point.

Feature: 70 directional vanes, 16.5mm air gap

Most aftermarket discs have 30 to 48 vanes.  Many times those vanes are straight, or non-directional, with a sub-optimal amount of space between disc faces.  After extensive CFD and thermal stress analysis, AP designed the Heavy Duty J Hook with 70 vanes and a wide 16.5mm air gap to increase airspeed and heat transfer, while reducing deflection and remaining reasonably lightweight.

Benefits

The increased directional vane count on the J Hook Heavy Duty Disc 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.

Feature: Exclusive AP Racing J Hook slot pattern

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.

Benefits
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 the slight increase in NVH for the serious enthusiast.

Feature: Complex metallurgy developed through 50+ years of experience

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). 

Benefits

Elite level teams choose AP Racing because they know the work has been done to provide the best available product at any price level.  The AP Heavy Duty J Hook is a direct derivative of AP's vast racing experience.  You can buy with confidence knowing that you're getting the best product available at any price point.  A note of caution however: the J Hook design is often imitated, and there are a number of lesser quality imitations on market.  Before purchasing, make sure you are getting an authentic AP Racing J Hook!

Feature: Reasonable replacement cost

Let's face it, no matter how good a brake disc is, it's still a consumable item.  They're no different than brake pads or gasoline.  You beat them up until they crack to pieces, then you throw them away.  If replacement iron is too expensive, you're always driving in fear, waiting to shell out big bucks for a new set.  Despite having the most expansive set of features on the market, the 325x32mm Heavy Duty J Hook's retail for a budget-friendly $249 each.

Benefits

Going to the track is expensive!   Event entrance fees, hotels, fuel, and tires all add up.  While you obviously want the best product available, you can't afford to pay a small fortune for something you're just going to destroy.  You can buy a cheap set of $150 discs for every event, have relentless heat issues, and find yourself constantly swapping them out.  Or, you can buy a high quality set that could potentially last you an entire season.  When you do the math, the long-term value of the AP J Hook's is tough to beat.  You'll enjoy all the benefits without breaking the bank, and you'll spend more time driving and less time wrenching.

Endurance testing at Essex- We know what you'll be doing to these discs, so we make sure they're up to the task.

Disc Bedding and Preparation

For an in-depth look at disc bedding, please visit the Essex Learning Center and watch our video entitled: How to Bed-in Brake Pads and Rotors.