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Essex/AP Racing 24 Hours of Le Mans-Capable Big Brake Solution now shipping!
Hi Gents,
Our latest brake solution is now ready to ship. We pulled no punches on this one, and it's literally as close as you can possibly get to the front brake system on the C7.R. It features AP's latest caliper technology and our newly designed 372x34mm, 84 vane endurance racing disc.
A few weeks back we launched our slightly smaller version of this kit, and it won a NASA National Championship race at Laguna Seca on its first time out! That result was very similar to the first ever use of a Radi-CAL caliper in pro racing, which was a race win at Watkins Glen in NASCAR Sprint Cup.
Summary of Benefits
Approximately 6-7 lbs. of unsprung weight reduction from EACH front corner of a C7 Z06, or 12-14 lbs. of total unsprung weight reduction from the nose
Only 3 lbs. heavier per side vs. the optional OEM C7 Carbon Ceramic (CCM) brake package!
Fits OEM C7 Z06 front wheels without a spacer
AP Racing Radi-CAL calipers are the stiffest, lightest, and most technologically advanced calipers available at any price
CP9668 calipers use a 25mm (1 inch) thick, commonly available brake pad shape
Ventilated, domed back, stainless steel pistons keep heat out of the brake fluid and provide an ultra-firm pedal
Mitigation of pad knockback via anti-knockback springs behind the caliper pistons
Anodized caliper finish that is resistant to wear and deterioration at elevated temperatures
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= less rebuilding and longer service life
No dust boots to burn up
Simple pad change with two bolts or quick-change spring clip, no caliper removal required
Lifetime professional caliper rebuilding support by Essex (at a fee)- pull off your calipers, send them to us, we clean, inspect, and rebuild them
Available disc burnishing service ensures that your kit arrives ready to be installed and driven hard immediately
Championship winning, 84 vane, fully floating, AP Racing J Hook endurance racing discs with 12 attachment points to hat
Below is the template inside of the OEM 19" front C7 Z06 wheel...plenty of room to spare, and will fit inside many 18" wheels.
What's In The Box?
• One pair AP Racing CP9668 Radi-CAL Pro5000R racing calipers
• One pair 372x34mm AP Racing CP6084, 84 vane, J Hook racing discs, with fully floating 6061 hard anodized aluminum hats and attachment hardware
• One pair caliper mounting brackets and hardware
• One pair Spiegler Stainless Steel Brake Lines with abrasion resistant coating
• Detailed installation instructions
• Brake pads are NOT included with our system. Racing brake pads are a highly personal choice. Many manufacturers include a set of inexpensive, low quality pads with their brake kits. Rather than artificially inflating the price of our system with a set of pads you probably don't want anyway, we've decided to remove the cost from our system and allow our customers to choose the pads that best suit their needs/wants. When purchasing our kit, you are able to choose one set of front pads at a 50% discount. This offer is valid on any of the brands/compounds that we offer.
Radi-CAL
“Radi-CAL” is a blanket term used to describe AP Racing’s patented asymmetrical brake caliper design. Radi-Cal technology is grounded in Computer Aided Design (CAD) and Finite Element Analysis (FEA), and allows for organic, alien-looking designs that are a radical departure from conventional caliper designs of the past. Radi-CAL's are widely considered the pinnacle of current brake caliper technology. Since their inception in 2007, these revolutionary calipers have amassed a lengthy string of race victories at all levels of professional motorsport, while redefining brake performance expectations. For more details on the design concept and what these calipers have achieved in professional racing, please visit our blog and read The AP Racing Radi-CAL Story.
The key benefits of the Radi-CAL design:
• Massive Stiffness Increase- A 30+ % increase in both static and dynamic stiffness vs. conventional calipers allows for far less deflection under load, which means superior pedal feel & modulation, more even pad wear, and longer caliper service life.
• Considerable Mass Reduction- Removing all extraneous caliper mass lowers the caliper weight, despite the huge stiffness increases.
• Optimized Airflow- Air moves around and through the caliper more efficiently, providing superior heat evacuation and cooling.
• Efficient Packaging- The asymmetric caliper profile and internal fluid porting allows the caliper to fit into tighter spaces.
CP9668 Pro5000R Radi-CAL
It has taken eight years, numerous generations of the design concept, and advancements in manufacturing techniques, but the Radi-CAL has finally evolved into a viable solution for racers and enthusiasts of all levels and budgets. While many products are supposedly born in racing, there can be no doubt about the Pro5000R pedigree. These calipers are direct descendants of the current crop of F1 and Sprint Cup calipers. They don't look ordinary, because they're not ordinary. They're the epitome of pure racing design: elegant, sparse, and brutally effective. And while they embody and employ the Radi-CAL design philosophy of the past, they also add some outstanding new features that enhance their practicality, convenience, and appeal. Quite simply, they are the lightest, stiffest, and most technologically advanced brake calipers that have ever been within the average enthusiast's grasp.
These intricate calipers have traditionally been machined from proprietary aluminum alloy billets. As one can imagine, machining away all of that material to achieve the final form is both time-consuming and costly. As a result, the price of these calipers has historically been prohibitive for the average club racer, time-trialer, or HPDE participant. Fortunately, the Pro5000R calipers use a new drop-forging technique that has dramatically lowered the manufacturing cost and the resulting price of entry, bringing this incredible technology to the masses.
Radi-CAL = Massive Dynamic Stiffness Increase
Over the years, many different strategies have been employed to shrink the brake caliper footprint while maintaining adequate stiffness: More robust caliper bridge designs, two-piece calipers with steel through-bolts, exotic materials (i.e. Beryllium, MMC), forging rather than casting, monobloc design, etc. All of these innovations pushed calipers towards becoming lighter, smaller, and stiffer. However, until the advent of the Radi-CAL, the same basic rectangular, boxy shape remained the accepted standard.
Is a rectangular box really the most appropriate and efficient shape for a brake caliper? AP Racing has now proven that it is not. As a brake caliper clamps brake pads against a spinning disc, a tremendous tangential friction force occurs between the pads and the spinning disc. In other words, the caliper is pulled strongly in the direction of the spinning disc, as represented by the downward pointing arrow on the right side in Figure 1 below. The caliper resists that force via the spindle hard mounting points, depicted by the upward arrow on the left. The dynamic load placed on the caliper twists or pulls the caliper into a parallelogram shape.
The dynamic force exerted on the calipers during a braking event is the key to the magic of the Radi-CAL design philosophy. Brake calipers of the past were designed to some extent in relative isolation from the forces that they were attempting to combat. They were designed to be the stiffest box possible while resting on a table, with much of the caliper mass residing at either end. The Radi-CAL is dramatically different because it was deliberately designed around the braking event forces that will be acting upon it. This is achieved by optimally distributing the body mass of the caliper on a diagonal, rather than at the two caliper ends. As such, the forces dynamically acting on the caliper are supported by the caliper mass, rather than what historically has been an empty box (see Figure 2 below). At the same time, this also allows for a significant reduction in overall mass, because all non-essential, non-load-bearing caliper body material is removed. So in the case of the Radi-CAL, it's not just about the material that is put into the caliper, it's about the material that is taken away!
Radi-CAL= Ultra-lightweight, Compact Design with High Airflow
As mentioned above, the Radi-CAL design philosophy is just as much about what isn't there, as it is about what is there. The Radi-CAL design relocates caliper mass, creating voids that would traditionally not be located where they are. As such, considerable mass is removed from the body, and the entire envelope of the caliper is optimized. The result is an extraordinarily lightweight and compact footprint. Whereas many competing six piston calipers weigh in the 9-12 lb. range, the CP9668 weighs an astounding 6.8 lbs.!
The Essex mantra when designing brake kits has always been, "Anything larger than necessary to get the job done is simply dead weight to drag around," and the Radi-CAL aligns perfectly with those values. One of the major problems with many of the brake packages currently on the market is wheel fitment. You’re offered gigantic discs and 12 piston calipers, with a pat on the back and a, “Good luck finding wheels to clear those things (insert sinister chuckle here).” The reality is that many casual racers want to use their OEM wheels on the track, or the smallest, lightest wheel they can find. Not only is saving unsprung weight critical, R compound tires are much more plentiful and cheaper for smaller wheels. If the components are designed properly with heavy use in mind, you don’t need to cram boat anchors under your wheels. If you’re worried about the loss of stiffness due to mass reduction, don’t. Some manufacturers use a heavier six piston caliper, but that's because the caliper wasn't designed or optimized for racing. In those cases, the same caliper may have been designed for use on much heavier road cars, and even trucks! AP Racing’s Pro5000R calipers are incredibly stiff, and designed from scratch with only the racetrack in mind.
Take a look at the caliper above or below. Anything else missing? Outer bleed screws and crossover tubes! The Pro5000R range has internal fluid porting and only two bleed screws located on the inner caliper half. That means that the chance of knocking a bleed screw or denting a crossover pipe during a wheel change virtually disappears. It also means that you now have half as many bleed screws to turn when changing your brake fluid. Eliminating the piping and bleed screws also allows the outer corners to be rounded, improving wheel spoke clearance.
Finally, take a look at the picture below. Compared to a traditional caliper, the pistons and brake fluid pathways have far more airflow between and around them, lowering the overall system operating temperature.
Two-piece, Drop-Forged Caliper Body
Radi-CAL's such as the one in Figure 2 above have traditionally been machined from a single, solid block of proprietary aluminum alloy (monobloc). With a monobloc design, the piston bores and piston seal grooves can only be machined with a right angle machine tool (the tool must be inserted up and into the caliper). As one can imagine, machining away all of that material with special tools and multiple setups to achieve the final form is both time-consuming and costly. As a result, the price of monobloc Radi-CAL's has historically been prohibitive for the average club racer, time-trialer, or HPDE participant. The Pro5000R has been made possible by a newly developed 2-piece drop-forging process, which allows a conventional machine tool to access the piston bores via a direct path. The result is a drastic reduction in both production time and cost, while still retaining an incredibly stiff form.
Hard Anodized Finish
The first obvious weakness when looking at a typical aftermarket caliper is the finish. Most aftermarket calipers come in a painted finish, whether they are red, black, or gold. That painted finish is designed to look pretty and prevent corrosion in harsh winter environment. Unfortunately, for all of the compliments painted calipers generate, there is an associated price if you drive the car in a track environment. That price is the chipping, flaking, fading, color shift, and general degradation of that finish in a fairly short period of time. Some OEM calipers can go from the as-delivered color to a nasty shade of brown in as little as one weekend. While this is typically worn as a badge of honor among our more hardcore customers, let’s face it…they still look terrible. More importantly however, all of those bits of paint end up in places they’re not supposed to, which we’ll get to in a minute.
Why does this happen? Heat. Paint and powder coat cannot adequately handle track temperatures. Powder coat also has some notorious issues with shrinkage. The powder coat layer expands and grows when the caliper is heated. When it cools, the powder coat doesn’t necessarily shrink in step with the caliper body itself. What’s left is a loose shell of finish hanging limply on the caliper body. That shell then cracks and falls to pieces.
Paint can also have similar issues depending on how it is applied. If you were to line up a few aftermarket calipers from the same manufacturer, you would likely see that the painted finish on each of those calipers is slightly different. Some have a thicker coat, some thinner, slightly different shades of red, etc. Painting is to some extent an art form, and must be performed in a tightly controlled environment. If it isn’t, you’re always going to see variation. A thick coat makes the part look soft around the edges, and is prone to cracking off in the same manner as the powder coat described above, leaving the underlying finish exposed. A part without enough paint will look uneven, and will not protect the underlying aluminum particularly well either. In addition to problems with cracking, flaking, and uneven application, paint and powder coat also experience extreme color shift when heated. Red becomes maroon or black, gold becomes brown, and black just gets uglier.
The calipers we are using in the Essex Radi-CAL Competition Kits are ultra-lightweight, stiff, and durable under all track conditions. The finish is a hard anodizing, which is the business under track conditions. When raw aluminum reacts with the oxygen in the air, a hard surface film develops on aluminum which prevents further degradation. The process is called oxidation, and you can think of it like rust. The anodizing process leverages this natural phenomenon, and takes it a step further to produce an extremely hard protective layer of aluminum oxide. It does so by running an electrical current through an acid bath, and dying it to the desired color. If you want to know more, Google it.
The result is a finish that is far more appropriate for racetrack use. Anodizing creates a uniform surface that is much more abrasion resistant than paint or powder coat. That means if you ding an anodized caliper with a box wrench when bleeding it, a big chunk of the finish isn’t going to chip off into your hand. While anodized calipers will still exhibit color shift, it will take a lot more heat to get them to change, and they won’t change as dramatically. More importantly though, you aren’t going to have bits of anodizing sticking to the sides of your pistons.
Brake Pads in A Commonly Available Shape
The basic pad shapes for the Pro5000R calipers were created by AP Racing many years ago, and are used by a wide range of racing calipers today. They're available in just about every popular racing compound on the market. That means you’ll never end up in a pinch without pads.
Below is a drawing of the basic pad shape:
Dimensions= 152.1 x 54 x 25 mm
Pad Retention Loop
The basic pad shape above comes from some manufacturers with a small loop on the top edge (the portion above the red line in the drawing above). On certain calipers a pad retention pin is placed through that loop to hold the pads in place. That small loop is not used in the AP Racing Pro5000R Radi-CAL's however, and must be removed for the pads to fit properly (it can be sawed or ground off in a matter of seconds).
Ventilated, Domed Back, Stainless Steel Pistons
There are people who will tell you that aluminum pistons are great for track calipers. They will tell you that the expansion rates of the pistons and caliper body need to be the same when heated. This argument is completely invalid and unproven. Those same people tend to get upset when you point out the fact that every serious race caliper, from every serious race caliper manufacturer on the planet uses either stainless steel or titanium pistons, period. There is a reason for this: they're better!
Stainless steel pistons are far superior to aluminum pistons in creating a thermal barrier. They are much better at keeping heat out of your brake fluid and preventing a soft pedal from fluid fade on the track. This has been proven over and over again at all levels of motorsport. While most aftermarket calipers use a pressed aluminum piston, the Pro5000R's use an expensive machined stainless steel piston.
To add stiffness to the pistons, AP designed the back of the piston with a domed back. At first glance this seems like a trivial design element. It is not. When domed back pistons were introduced in professional racing, driver feedback was immediate and resoundingly positive. The domed back adds considerable stiffness that can be felt through the pedal, and they have now become the standard vs. which all designs are judged.
For even greater heat resistance, there is ventilation on each piston. The air gaps around the piston edge allow for even more cooling air circulation around the pistons. All of these features slow and repel the influx of heat into the brake fluid, preventing brake fluid boiling and fade.
Anti-knockback Springs
Not only are the pistons stainless steel, they are also fitted with anti-knockback springs. Springs in pistons you ask? Yes, springs. If you’ve ever gone through a series of S turns and then had your pedal drop when going into the following brake zone, you have experienced knockback. To say it is disconcerting is an understatement. You’ll often see pro drivers ‘pre-tap’ their brakes lightly when approaching a brake zone. They are fighting knockback.
Knockback is a phenomenon that is common with fixed calipers. Knockback occurs when your car’s wheel, hub, and bearings deflect during cornering, allowing your brake disc to move out of sync with your caliper and brake pads. The amount of knockback varies by vehicle, and depends on the amount of deflection seen in the parts listed above. As the brake disc deflects, it actually pushes the pads away from each other, forcing the caliper pistons back into their bores. The piston seals don’t have enough tension in them to completely return the pistons to their original location. That means there is slack in the system that needs to be taken up. When you press the brake pedal, it will continue to drop until that slack is taken up.
Anti-knockback springs help alleviate this situation by putting some tension on the back side of the pistons. When the disc deflects and makes contact with the pistons, the springs push the pistons back into their proper location, reducing slack in the system. That means less pedal drop and far fewer pucker-factor moments when going into heavy brake zones.
There are no major downsides to lightweight AKB spring as long as the caliper is designed to accommodate them. More specifically, AKB springs do not create any increased drag or wear on the pads and discs as long as the shape and material of the piston seals takes them into account.
As you're driving the suspension is constantly compressing, the disc is moving around laterally, and the pads are being pushed slightly away from the disc. Think of the seals in the caliper as a spring or hinge attached to the side of the piston, rather than just a ring through which the piston slides. In an AP Racing competition caliper, the groove in which the seal resides isn't a square cut groove.It has angles. When the pistons slide in or out there is friction between the outer piston wall and the seal, and the seal distorts a bit as shown in the illustration below.
A caliper piston sliding out to the left would distort the seal in this manner (the slashes are the seals on either side of the piston):
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As the piston slides back in to the right, the seal does this:
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/
There is a certain amount of tension or friction that needs to be overcome before the piston actually starts moving through the seal ring. That tension/friction keeps the piston from dragging on the disc once the pistons are pushed back into the bores by the disc/suspension movement.
When AKB springs are added, a little more force is required to push the pistons back into their bores than would be required without them. After the spring is compressed, it unloads and pushes the piston back to 'neutral.'
With the proper seal and spring the goal is to keep the piston in the 'neutral' position, not pressed against the disc. The piston is still able to slide freely in either direction, but a bit of friction or tension needs to be overcome initially to get it moving in either direction. The seal offers that first bit of friction to limit movement, and then the spring provides additional resistance. The end result is that the properly designed AP Racing calipers won't drag or create additional or unnecessary wear.
High Temperature, Low Drag Seals Without Dust Boots
We are often asked by potential customers if the calipers in our kits require frequent maintenance and rebuilding because the pistons don't have dust boots. We are perpetually shocked by this question because it makes no intuitive sense. If you have a product that is specifically designed to handle the extraordinary high-heat conditions of track use, why would it require more maintenance when used under those conditions vs. brake components that were designed to cruise around on the streets at low speed and temperature?
Many people confuse piston seals with dust boots. All calipers have seals. They're the little rubbery rings inside the piston bores (see pic below). If a caliper didn't have a seal, your brake fluid would leak out around the pistons! OEM caliper seals aren’t designed to handle constant trips to several hundred degrees without becoming brittle and leaking. Our calipers use special high-temp seals designed for track use. They are the exact same high temperature seals used in NASCAR Sprint Cup, ALMS, DTM, etc. That means they are less likely to get brittle and wear out when used under high-heat track conditions, and they require far LESS frequent replacement and servicing.
Most aftermarket calipers are designed for year round road use, and as such come with a bellows style external dust boot like the ones shown below. The rubber boot stretches as the piston extends, and its objective is to keep contaminants out of the piston bore. It's a nice concept, but we've seen customers burn those up in a single 20 minute track session! Once that happens, you're simply driving around with some tattered, burnt rubber bits attached to your pistons. At that point they're providing zero benefits to you. If you're going to instantly destroy them when you go to the track, why worry about having them in the first place? We skip making that mess for you by eliminating them from our design.
Simple Pad Change with Two Bolts, or Quick-Change Spring Clip
After the countless times you’ve changed your brake pads, you’re probably never too excited when it comes time to do so. Changing pads will no longer be a chore with the Pro5000R's. No more fiddling with a hammer, punch, or pliers. AP’s bridge bolts pop out easily with a 5mm hex wrench and a 7mm socket. It will take you longer to pull off the wheel than it will to change pads. Less time futzing around in the paddock, and more time driving= fun.
The CP9668 caliper even takes things a step further in terms of convenience, and includes two bridge options as standard. You can use the fixed bridge, or you can install the included quick-change spring clip. To open the spring clip, you just squeeze and lift. Changing pads has never been faster or easier!
Discs- AP Racing Competition J Hook
The AP Racing J Hook discs in our system 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 even championships (ALMS, Rolex, Grand Am, 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.
Mounting Hardware and Anti-Knockback Spring Clips
If you look closely at the mounting hardware we use in our Competition Kits, 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.
As discussed above with regards to the piston springs, knockback can be a serious issue when tracking a car. 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.
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.
Internal Vane Quantity and Quality
The internal vane design on AP J Hook discs is quite a bit different vs. OEM-style discs and other brands of aftermarket discs. Many OEM discs feature a pillar vane design, which can be thought of as a group of posts or pillars connecting the two disc halves together (see pic below). The pillars are not organized linearly from the outside to the inside of the disc, and turbulence is created as air flows through and among them. Pillar vane discs are therefore not particularly well suited to heat evacuation. The goals of a pillar vane design are disc face stability for low nvh (noise, vibration, harshness), and a low cost of production. Pillar vanes are non-directional, and the same part number is used on both sides of the car (again for cost reduction).
Other OEM discs feature a straight, non-directional internal vane. While that type of vane flows more air than a pillar, it does not move nearly as much air as the directional vanes featured in AP Racing's discs. Having directional vanes means that AP Racing discs are handed. There is a unique left disc and a right disc in each pair, and they cannot be swapped from side-to-side on the car. The orientation of the vanes is optimized to spin in a certain direction, pumping the maximum amount of air possible through the disc. The shape of these internal vanes is also optimized to promote smooth airflow.
In addition to having a superior internal vane design, AP Racing discs have far more of them! Most aftermarket discs have 30 to 48 vanes. After extensive CFD and thermal stress analysis, AP designed the J Hook's with a high vane count (typically 60 to 84 depending on application). Having more vanes increases airspeed and heat transfer through the disc, reduces air recirculation between vanes, and reduces deflection at the disc face. Compared to an OEM-style disc or competitor's 48 vane discs, the 60+ vane discs are less prone to coning, distortion, and cracking, while providing less brake fade, reduced judder, more even pad contact, and a longer service life.
Below is a comparison of a one-piece OEM pillar vane disc and an AP Racing two-piece J Hook. A few things to note in these pictures: The AP Racing disc has a much wider air gap between the disc faces, allowing considerably more airflow into and through the disc. The uniform, directional vane design also contributes heavily to superior airflow.
Most of the cooling air that enters a brake disc comes from the back side of the discs, particularly if brake ducts are being employed. The top disc is an OEM pillar vane. The second disc is an OEM dual-cast disc (which is technically a two-piece disc). The bottom disc is the AP Racing J Hook. Which of these discs do you think will flow the most air? While the OEM discs have narrow inlet port and/or obstructions blocking the disc vanes, the AP Racing disc offers a clear path for cooling air to enter and flow through the disc. The result is significantly cooler discs that are less prone to cracking and wear.
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.
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 themself 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.
Initially, we will only be burnishing our brake kit discs with the Ferodo DS1.11 pad compound, but will likely expand the program to other compounds in the future. If you decide to select this option, the discs in your brake kit will arrive covered in a beautiful transfer layer of DS1.11, ready to drop on the car for instant abuse. The cost of our burnishing service is $50 per disc ($100 per brake kit).
Please note that the pads you receive will not be pre-burnished. In other words, the pads and discs do not have to be a matched set burnished together to reap the benefits the procedure has on the discs. In other words, we will burnish the discs in the pad compound you choose, they just won't be burnished with the exact set of pads that will arrive with your kit.
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 J Hook's are completely affordable.
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 discs for every event, have relentless heat issues, and find yourself constantly swapping them out. 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.
Elite level teams choose AP Racing discs because they know the work has been done to provide the best available product at any price level. The AP 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.
Caliper Brackets & Hardware
Caliper brackets for our kit are machined from heat-treated 6061 T6 billet aluminum, and hard anodized, ensuring strength and durability. All included hardware is of aircraft quality, and identical to what we use in professional racing. One of the nice features of our brackets is their cutaway design, which allows for the snug fitment of many currently available brake duct kits.
Spiegler Stainless Steel Brake Lines
Our Competition Kits include a set of the highest quality stainless steel brake lines available. Spiegler lines have a wide range of features not available in competitive offerings. Below are just a few. For complete details please visit the Spiegler page on our site.
Last edited by JRitt@essex; 12-07-2015 at 08:06 AM.
I'm really looking forward to getting these. Too bad they didn't make it in time for VIR this weekend but that'll let me burn up my old pads.
Sorry we couldn't get it buttoned up in time! I believe your kit is shipping today. Keep an eye out for a tracking email, and thanks again for the purchase. You will certainly not be disappointed.
Kit looks stunning and what a write up!
Thank you very much. These kits are all about the details! An immense amount of time was spent on their design, using all of the latest racing technology. Every component has a purpose, and that purpose is running cooler, lasting longer, and/or being lighter. The kit's ultimate goal is making the car easier to drive faster for longer. I'm confident that these kits will prove to be the definitive brake solution for the C7 chassis, just as our C5 and C6 kits have proven to be on those platforms.
Just wanted to comment on template fitment - based upon the template I printed out (and verified dimensions), I have nearly 1" clearance on my Finspeed 18" wheels. I have 18x11 front wheels and could slide my fingers between the template and the wheel no problem.
Obviously check yourself, but I was happy to see how much clearance there is.
Just wanted to comment on template fitment - based upon the template I printed out (and verified dimensions), I have nearly 1" clearance on my Finspeed 18" wheels. I have 18x11 front wheels and could slide my fingers between the template and the wheel no problem.
Obviously check yourself, but I was happy to see how much clearance there is.
Excellent! Do you have any additional details on the wheels (exact model name, offset, picture)? I'd like to add them to our new website as a confirmed fitment. Thanks so much!
Excellent! Do you have any additional details on the wheels (exact model name, offset, picture)? I'd like to add them to our new website as a confirmed fitment. Thanks so much!
Sure thing, mine are Finspeed F110 with deep concave, and knurled bead in 18x11 - they handle the offset.
I think I might have been the first person to try this setup on a C7Z on track so I wanted to post up my impressions. Let's start with the install.
As Jeff said above the kit includes stainless brake lines and to be honest swapping those out was the most difficult part of the install. It's just a pain to get the connectors to the hard lines off and on but once I got one side done the other wasn't so bad. This thread has the blow by blow - https://www.corvetteforum.com/forums...ake-lines.html. Once the lines are swapped the install is very simple and the instructions very good. Anybody should be able to do this as long as you have the right hand tools and torque wrench.
First impressions, this kit certainly looks impressive. The calipers look like artwork and the pads are massive. I rolled up to tech inspection and the guys working were trying to figure out whether that really was the pad or a part of the caliper. What I noticed though were the little things. Put a box end wrench on the stock bleeders and then put it on the bleeders on the AP racing caliper. The AP Racing ones fit the wrench like a glove with no play and the metal actually feels harder than the stock (or even other aftermarket) bleeders. Are they really chrome Jeff? That should count for cars and coffee points too
My first event was two days on Summit Point's main circuit and consisted of eight 25-minute sessions. I was on Hoosier R7 and this is the event where I turned the 1:16.8. I ran the DS 1.11 pads front and rear and my goal was to flat out abuse these brakes and see if I could brake them.
Once I felt things out and made sure the pads were bedded I was in the gas longer, braking harder, and later than I ever had and the brakes flat worked without any fade or long pedal. When you adapt to the fact that aero actually gives you more traction at higher speeds it's amazing just how hard this car will brake with sticky tires. The feel of this setup with the DS 1.11 pads is similar to the stock steel setup which I liked because it makes it very easy to modulate the brakes during trail braking.
At the end of the two days I pulled the pads and measured them. They averaged around 17mm from the starting depth of 25mm. I really was hoping for the same results the owner of the C5 racecar had where his pads hardly wore after an entire race weekend but I think the extra weight and lack of cooling of the C7Z shows itself here. Everything worked great but don't expect to go all season on a set of pads either. As a side note, my rears are also wearing much more quickly that before which I attribute to the fact that I am pushing the brakes harder now.
After sharing the results with Jeff we decided to try out the DSUNO fronts with the DS 1.11 rears last weekend. Same track, same number and duration of sessions.
I should note that the DS 1.11 don't seem to need a lot of heat to work well. Usually I can pit out and get them up to temp by the time I'm through T1. The DSUNO definitely need more temp to work well and for that first lap or so you can feel that the rear DS 1.11 were working a lot better than the front DSUNO. They still work, just not as well as once they are heated up and they were always up to temp before the tires were anyway.
The DSUNO definitely has higher torque and if you like to get more braking with less pedal effort this is a better choice. To me they felt more like the CCBs than the stock steel system and it took me a while to get dialed in so I wasn't overslowing the car at the end of the front straight but when I did I was braking later than before.
Again I pulled the pads after the event and measured them. The pad wear was slightly better than the DS 1.11 and it appeared to be more consistent across the pad. I'd need to run some temp paint on the rotors to confirm but I suspect the DSUNO is better suited to the temp range generated by this car with it's lack of cooling. I'm sure Jeff will chime in here. I did run temp stickers on the outside of the calipers at the first event but they hardly registered.
I have a set of DSUNO rears on order and plan on testing DSUNO all the way around at VIR in a couple of weeks. At this point I absolutely love the AP Racing kit but I'm not sure which compound to go with. Pending the results of my next test I'd say it really comes down to the feel you like.
Our engineers and technicians agree that the brake lines on the corvettes are the biggest pain of any we've ever dealt with! Space is at a premium and it's tough to maneuver around the hard line connection. Thank you for going to such lengths to describe working with and around them.
One of the great things about our setup is the ability to tinker with pads and adjust to taste (something that really can't be done with CCM discs and factory pads). For experienced drivers/racers, the feel and confidence aspect is irreplaceable. I think that comes across in your post, and is something that we frequently hear about our kits.
The DS1.11 and DSUNO definitely feel very different from each other. As we've had more and more customers try both, they seem to be split down the middle on their preference. The more people that we have trying both compounds however, the more we're finding that the DSUNO's are wearing longer than expected, and similar to the DS1.11. I recently had an e92 M3 big brake kit customer abroad tell us something similar running Sepang Circuit...he started on the DS1.11, switched to the DSUNO, and actually had better wear rates from the DSUNO (he also liked the feel of DSUNO better). I think maybe Ferodo was just underselling us a bit on the DSUNO's capabilities. At this point, my standard recommendation is shifting towards starting people out on the DSUNO, rather than the DS1.11 (which is what we have recommended as a starting point in the past). I'm thinking DSUNO at both ends of the car could be the way to go for most people.
At any rate, we're going to be doing some internal dyno testing at Essex over the winter on both compounds, along with some new variants of both. Ferodo has been really great to work with, and they're all about continual improvement and development.
These cars are definitely wicked on brakes...the fronts in particular. Definitely more so than any C6 or C5 we have seen. I'm looking forward to getting some accurate temperature readings from the discs and calipers. I would like to see a bit more pad life than what you saw. As you mentioned, we had one C5 Z06 customer run an entire race weekend with our Pro5000R Radi-CAL kit (and ducts) with barely any pad wear, so it's clear you're pouring a lot more heat into them and could use some airflow. That said, you ran eight 25 minute sessions intentionally trying to pummel the brakes, and still ended up with pads that were thicker than the OEM ones are when brand new/unused (16.5mm)...a very good thing.
Everyone should be running cooling ducts on pretty much every car being tracked. The overall benefits to moving air through the discs is huge in terms of both fade resistance and component longevity. That said, I know it's a real bear on this car, and nobody seems to have a good solution yet. We spent a long time poking around on our Z51, trying to figure out a good solution. The problem we face is how to build an effective set-up while keeping the cost at a reasonable level. I have no doubt we could build a really killer custom solution, but I'm just worried it will be too expensive. I'm going to take this one back to engineering and see what we can do.
What I noticed though were the little things. Put a box end wrench on the stock bleeders and then put it on the bleeders on the AP racing caliper. The AP Racing ones fit the wrench like a glove with no play and the metal actually feels harder than the stock (or even other aftermarket) bleeders. Are they really chrome Jeff? That should count for cars and coffee points too
Lol. I think on the next iteration of these calipers we should go with diamond covers for the bleed screws. Now that would offer some serious C&C points!
Once I felt things out and made sure the pads were bedded I was in the gas longer, braking harder, and later than I ever had and the brakes flat worked without any fade or long pedal.
That right there is what it's all about.
Thanks again for the thorough and articulate feedback Poor-sha, and I'm glad you love the kit!
We've had several customers ask us for more details on weights and dimensions. Our CP9668/372 brake kit falls about halfway between the OEM CCM and Iron setups in terms of overall weight.
I've also had several people ask, "What about running an iron disc in the OEM CCM size?" As mentioned previously, the big issue is that the CCM discs are built larger than their iron counterparts to aid in heat dissipation. The goal with the CCM discs was to add surface area for heat radiation. That means an iron version of them will be far larger than is required and will weigh a ton. We currently sell a 398x36mm iron disc with 84 vanes, which is very close to the Z06's CCM size of 394x36mm. Our 398mm disc weighs 28-29 lbs. with the hat. That means the following if you have a Z07:
Since getting weight off the nose of these cars is neither cheap nor easy, that's obviously not the ideal path.
Here's how it breaks down:
*All numbers below are per side*
OEM front Caliper= 10.4 lbs
OEM front CCM Disc=13.4 lbs.
OEM front pads= 6.2lbs Total OEM CCM front corner brake weight= 30.0 lbs.
AP Racing CP9668 + bracket = 7.9 lbs.
AP Racing CP6084 372x34, 84v disc/hat= 21.1 lbs.
FRP3014 Pad set for CP9668= 6.35 lbs. Total AP Racing CP9668 front corner brake weight= 35.35 lbs.
OEM front caliper= 10.4 lbs.
OEM front iron disc/hat= 23.8 lbs.
OEM front pads: 6.2lbs Total OEM Iron front corner brake weight= 40.4 lbs.
Projected front weight using OEM CCM calipers and iron discs in OEM CCM size (394x36mm)
OEM front caliper= 10.4 lbs.
front iron disc/hat in CCM size= 28 lbs.
OEM front pads: 6.2lbs Total front corner brake weight using OEM calipers and an iron disc in the OEM size (394x36mm)= 44.6 lbs.
A few more tidbits...
Pads for OEM caliper=16.5mm thick
Pads for AP Racing CP9668 caliper= 25mm thick
OEM Iron 370x34mm
Vane style= non-directional pillar
# of vanes= 37 outer
AP Racing disc 372x34mm
Vane style= curved directional
# of vanes= 84
I just got these today from Jeff, and all I can say is WOW. I expected the brakes to be big, but I guess my expectations were dramatically different than reality. The pictures on this thread are great, but they don't capture the massive size of the caliper. This doesn't either, because the depth is probably more impressive than the width. These are so obnoxious in a good way - and the rotors are probably just as impressive. I am very impressed!!!
I just got these today from Jeff, and all I can say is WOW. I expected the brakes to be big, but I guess my expectations were dramatically different than reality. The pictures on this thread are great, but they don't capture the massive size of the caliper. This doesn't either, because the depth is probably more impressive than the width. These are so obnoxious in a good way - and the rotors are probably just as impressive. I am very impressed!!
09-09-2015, 11:07 AM
Essex/AP Racing 24 Hours of Le Mans-Capable Big Brake Solution now shipping!
Space is at a premium and it's tough to maneuver around the hard line connection. Thank you for going to such lengths to describe working with and around them.
