AP Racing 372x34mm Replacement Ring

AP Racing replacement 372x34mm J Hook rotor discs are used in many of the AP Racing brake kits. These replacement rotor ring measures 372mm x 34mm and features 72 directional cooling vanes. The AP Racing 13.05.10052 and 13.05.10053 rotor rings are directional, curved vane, heat treated and stress relieved. These are the exact AP Racing  rotor rings as CP7177-350GC and CP7177-351GC with the USA AP 13.05.10052 and 13.05.10053 part numbers. Same rings, different part part numbers.

AP Racing J Hook Competition Disc Replacement Ring 372x34mm Details:

• Manufacturer: AP Racing
• Manufacturer US part number right: AP-13.05.10052
• AP Racing part number right: CP7177-350GC
• Manufacturer US part number left: AP-13.05.10053
• AP Racing part number left: CP7177-351GC
• Slotted face: Yes
• Diameter: 372mm (11.65")
• Thickness: 34mm (1.34")
• Hardware included: No
• Torque specs for this disc and hardware assembly: 124 lb-in

Iron Disc Benefits

So what can AP Racing J Hook iron discs do for a car previously equipped with carbon ceramic discs?

• Increased airflow and slower heat transfer to other brake components- AP Racing J Hook discs have a unique, high-count vane design that promotes airflow, heat evacuation, and rapid cooling. They don't rely on a large surface area to cool via radiation. The iron discs will move more air than your carbon ceramic's, and as a result they won't heat your brake pads, caliper pistons, and brake fluid up as quickly. You'll be able to run longer sessions without brake fade, and you'll enjoy the confidence that comes along with them. They'll also make any brake ducts that you have on the car more effective and useful.
• Huge range of compatible brake pad compounds- Iron discs will open up a much greater range of available brake pads. You'll be able to achieve a different feel, and tailor your brake setup depending on your needs and environment, whether that is running an AutoX or the most demanding racetrack in your area. You'll also likely be paying less per brake pad set than you were previously, and your pads will last longer.
• Inexpensive spare discs- You'll no longer have to spend thousands of dollars when it's time to replace your discs. AP Racing J Hook's typically only cost $400-600 per iron disc ring, so you won't have to stress about anything happening to them. They're inexpensive enough that you can always keep a spare set on hand, so you won't have to worry about any brake-related downtime when you're out at the track.
• Durability- Iron discs can take a beating. You can stash your spares in your race trailer, and you won't have to worry about handling them, covering them, dinging them, or chipping them when changing your wheels.

As you can see, although iron discs do come with a slight weight penalty, they're still the smart choice if you run your car hard on the racetrack. They're the obvious solution that has been proven countless times on tracks around the world, at all levels of motorsport.

Among iron disc choices, there are none better than AP Racing J Hooks. AP Racing J Hook Discs are the epitome of endurance racing components. They will hold up extremely well to any abuse you plan to throw at them. These discs have been proven time and again in professional racing, winning many races and championships (SRO, IMSA, WEC, Rolex, etc.).

Two-piece Floating Design with Aluminum Hat

As is the case with most metal, iron brake discs grow substantially when heated. As it is heated, a disc expands radially, increasing in diameter and circumference. One-piece disc designs run into problems when this occurs. Look at the picture below and imagine the disc is being heated on the track. As the disc expands, the outer edges of the disc are pulling away from the center of the disc, but there are no built-in provisions to allow for that expansion. The edges of the disc therefore pull, lift, and distort, which is called coning. Now imagine that disc vertical on the car, running in your caliper. Coning directly impacts the brake pads’ contact with the disc, leading to uneven wear and tapering, and even a long brake pedal.

Two-piece discs on the other hand, compensate for the expansion of the disc as it heats. This is accomplished by building ‘float’ into either the disc itself, or the disc hat/bell. In this case, the float is in the disc. If you look closely at the picture below, you can see that the mounting holes for the hat attachment bobbins are not round. They are an oblong shape. These channels allow the hat mounting hardware to slide as the disc is heated and expands, allowing the disc to run true in the caliper without distortion. That means less distortion, stress cracks, and pad taper.