New AP Racing Sinusoidal "Wave" Vane Technology Makes its Production Car Debut on the 992 GT3

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 (ALMS, Rolex, Grand Am, etc.). On the front 2-piece discs for the 992 GT3, we are introducing a new internal vane technology from our motorsports experience. It is called the Sinusoidal Vane, which AP sometimes refers to internally as the 'Wave' Vane for obvious reasons as you’ll see below. This tech is something that has helped AP Racing brake systems win championships in international GT racing, as well as multiple NASCAR Cup championships here in North America. As one of the most desirable track weapons on the planet, we wanted the 992 GT3 to be the first production car application for this technology in North America. Just as AP Racing's Radi-CAL calipers set a new benchmark for caliper stability, cooling, and durability, the Sinusoidal Vanes have done the same for iron racing discs.

The concept for this disc design originated in NASCAR Cup. Up until the debut of the Next Gen car (for which AP/Essex are supplying the spec brake package), we were cramming our brake systems inside tiny 15” wheels. Trying to squeeze adequate brake thermal mass into a wheel that small is incredibly challenging, particularly when you have a 1,000 HP and 3,000 pounds mashing on them every few seconds from 200 mph…for hours on end! In a wheel that small, there isn’t anywhere for the heat to go, and the durability of every component is crucial. We were constantly looking for ways to provide the Cup teams with increased durability, stability, and cooling, and that’s what led AP to this technology.

 

Benefits of the Wave Vane disc technology vs. traditional curved vanes:

• Increased thermal stability- Wild temperature swings are what causes discs to crack. When you stand on the brakes for an approaching corner, your disc temperatures skyrocket and the iron expands. As you travel down the subsequent straight, the discs are blasted with cooling air. The longer the straight and the higher the speed, the greater the temperature drop, and the further the iron contracts. This expansion and contraction cycle places a huge amount of stress on the iron and is what causes them to eventually crack. That’s why tracks with relatively slow corners at the end of high-speed straights, followed by another long straight, decimate brake discs (think Watkins Glen or Road America). In an ideal world, once you brought your discs up to race temps, you would keep them at a constant temperature for the entire session. The Sinusoidal Vane brings the discs closer to that goal by decreasing the difference between the maximum and minimum disc temperature by as much as 35%. That means a less dramatic temperature swing and greater crack resistance and durability.
• Reduced maximum disc temperatures by 10%+: Not only are temperature swings less intense with the Wave Vane, the maximum temperatures reached are substantially lower. For example, in one NASCAR test the Wave Vane discs showed a peak temp of 1328F and a minimum temp of 1085F (delta of 243F), while the traditional curved vanes maxed out at 1490F and a min of 1121F (delta of 369F). Not only was the difference between min and max more subdued, the max temperature reached by the Wave Vane disc was 162F lower!
• Increased cooling surface area- Each of the internal Wave Vanes has a larger cooling surface area vs. a traditional curved vane.
• Greater support for the disc face- A disc’s internal vane structure provides the support lattice behind the disc face. Having many internal vanes impacts airspeed and heat transfer through the disc, reduces air re-circulation between vanes, and reduces deflection at the disc face. In practical terms, a disc with a high number of vanes is more thermally stable, maintains more even contact with the brake pads (which reduces uneven pad deposits/judder), and is less prone to distortion. In summary, the Wave Vane design provides even greater support for the disc face than AP’s standard curved vane designs.
• Reduced weight- The Wave Vane design provides a slight unsprung weight reduction vs. a similar disc with curved internal vanes.

In summary, this new disc technology continues AP Racing’s perpetual quest for faster, lighter, stronger, and more durable brake components.

 

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.

 

Mounting Hardware and Anti-Knockback Spring Clips

If you look closely at the mounting hardware we use on our Competition Discs, you’ll notice a few details that are often overlooked in lesser products. These components are specially made for their intended purpose. These are not cheap bolts found at your local big box store. They are custom made in the USA for Essex and AP Racing, and they are the exact same components we use on professional racing products.

In order to help control the lateral motion of the disc, which pushes the pistons back into the caliper, we use an anti-knockback spring clip on every other disc attachment point (on a ten bolt disc there are five spring clips, while on a twelve bolt disc there are six). These spring clips help keep the disc hat and iron ring in alignment, while still allowing the disc to expand and float radially. As an added bonus, they prevent the hat and iron disc from rattling and making noise.

 

Hat Design

Floating two-piece discs also have the added benefit of reducing heat conduction to the hubs and bearings, decreasing wear and tear on these costly components. The disc hats themselves are manufactured from 6061 heat-treated billet aluminum, with a hard anodized coating. This material was specifically chosen for its strength at high temperatures, as it will be in direct contact with the searing hot iron discs. The hats feature scallops on the underside, to allow for heat evacuation along the outer disc face once installed.

 

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.

The OEM discs avoid this problem by simply leaving the face blank. While the risk for NVH goes down, so does the pad bite and feel of the disc through the brake pedal. Competitive aftermarket offerings typically have straight slots, which tend to leave cool spots across the disc face between the slots.

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, and particularly a plain-faced disc. 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 750 Formula 1 races! 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). The primary objectives with OEM discs are simple: they must be cheap and easy to produce. The design objectives for these two products are vastly different.

 

Disc Burnishing/Bedding Service

If your brake discs aren’t being properly prepared for abuse prior to flogging them on track, you’re exposing yourself to potential judder, vibration, and cracking issues. We all know that prepping your pads and discs at the track can be difficult. Doing so wastes time during the first session of the day, and it's a hassle and potentially dangerous for other drivers as you go through the procedure. Track time is expensive and tough to come by. The more time you spend behind the wheel performing an elaborate bed-in procedure, the less time you’ll spend doing hot laps. Performing the procedure on-track also limits its repeatability. You can't control what's going on around you with track conditions, other drivers, etc., and many track configurations don't really lend themselves to the constant start/stop/start required to do the job properly.

Essex is now offering a solution via our professional burnishing service. Previously reserved for our professional racing customers, we are now offering our retail customers the option of having the discs in select Competition Brake Kits pre-burnished at our factory. We burnish thousands of discs for the top racing teams each year. After countless hours of experimentation, and extensive feedback from the top drivers and teams, we can consistently squeeze the most reliable performance out of AP Racing's discs. The procedure is incredibly repeatable, as it is performed on a computer-controlled machine by experienced technicians.

The cost of our burnishing service is only $50 per disc, making it an affordable, time-saving option that will produce far more consistent and safer results than trying the procedure on your own. Message Info@GMPperformance.com to add burnishing to your brakes.