C6 Corvette Brake Package - AP Racing Front Big Brakes 4-Piston (Sprint)

Option Selected: Kit with-out Brake Pads
SKU: 13.01.10008-BUN
Manufacturer Part Number: 13.01.10008-BUN
Availability: Usually Ships In 3-5 Days
If you owned and tracked a C5 or C6, you probably view the front OEM brake system as a weakness of the car. They were more than adequate for street use, but didn't really live up to the performance potential of the platform overall, particularly on the Z06 or after the car was modified. While that isn't an uncommon situation with factory brakes, there simply wasn't much 'headroom' built into the system. The brakes on the C5 are improved compared to the older cars, but still leave a lot to be desired for heavy track use!

Complete front brake system for C5, complies with SCCA T1 regulations
Clears OEM C5Z06 front 17" and rear 18" wheels (when run on front)
Discs are interchangeable with base C5 OEM discs
Caliper pistons sized properly to allow for seamless integration with OEM master cylinder and ABS system
NASCAR/ALMS Racing Series Technology for the street!
Easy pad replacement with-out having to remove calipers.
Lighter than stock calipers.
Many brake pad options, to choose from.
Brake Pads and Brake Fluid sold separately.

Kit Includes:
One pair AP Racing CP8350, four piston forged calipers
One pair 325x32mm AP Racing CP3908, heavy duty J Hook racing discs, with fully floating 6061 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. The available pad compounds that Essex sells for the CP8350 caliper can be found here. When purchasing this brake system, you have the option of buying one set of any of the pads in that link for $25.

The first obvious weakness when assessing the OEM Stingray calipers is the finish. They come from Bowling Green painted in a variety of colors for corrosion resistance and appearance. Unfortunately, for all of the compliments pretty painted calipers can 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 decimation of the finish in a fairly short period of time. 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 though, all of those bits of paint end up in places they’re not supposed to, which I’ll get to in a minute. Below is a picture of a factory Lancer Evolution caliper that was used heavily on the track. These calipers are very similar to those that come on the front of the Stingray. Believe it or not, this caliper used to be red!

Why does caliper paint peel or crack? Heat. Paint and powder coat cannot adequately handle the temperatures that calipers hit when run on a track. Powder coat also has some notorious issues with shrinkage. The powder coat layer expands and grows when the caliper is heated. When it cools however, 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.

Essex and AP Racing have teamed up to create the ultimate Sprint brake system for C5 Corvettes. Designed specifically to comply with SCCA T1 regulations, this brake system provides a laundry list of benefits for any Corvette racer or track enthusiast. The system was designed with the, "bigger isn't always better" philosophy firmly in mind, and every component in the system was carefully chosen to eliminate weight, improve durability, and keep consumable costs (pads and discs) at a minimum.

Our system is built around real race parts, not modified street parts. That means no disintegrating dust boots or faded red paint. It also means that you finally have the chance to get your hands on technology that has traditionally been reserved for professional racers: Stainless steel pistons, anti-knockback springs, high temperature seals, 70 vane racing discs...the list goes on.

We gathered quite a bit of customer feedback during the development of our system, and did our best to integrate as many customer requests as possible. As a result, our system offers a number of unique features not offered by other products on the market:

Complies with SCCA T1 rules for C5 Corvettes
Clears OEM C5Z06 front 17" and rear 18" wheels (when run on front) without spacer
Included AP Racing discs are the same size as OEM C5 discs, allowing them to be interchanged at will
(Please note, OEM-style replacement discs from different manufacturers have varying tolerances. Essex cannot guarantee interchangeability with all 1-piece OEM style discs.)

Caliper pistons sized properly to allow for seamless integration with OEM master cylinder and ABS system

Please do keep in mind however, that every yellow AP logo is hand painted on the caliper. It will degrade over time, particularly if you slop brake fluid all over it. Our customers asked us for something with at least a little visual punch and some brand recognition, so we had to give them this token. Also keep in mind that an anodized finish is not designed to be driven through road salt.

Okay, so we’ve established that paint and powder coat are not ideal choices for calipers that will be thrashed at several hundred degrees on the track. While the finish is the most blatant feature that people key in on, it’s actually not nearly as important as some of the other features in the caliper that allow it to operate efficiently at track temperatures.

20mm Thick, Inexpensive Brake Pads

Race pads aren’t cheap, and you burn through them quickly if you spend any amount of time on track. The average set of race pads for the OEM Corvette calipers are more expensive than the ones for our AP Racing CP8350. In many cases, the OEM shape is $100 more per set for the same compound. How many sets of brake pads do you go through in a season? Some people find that they could pay off their brake system in a short period of time on pad savings alone.

Also, since the pad shape for our caliper is used by a wide range of racing calipers, it’s available in just about every popular racing compound on the market (Essex alone sells close to 20!). That means you’ll never end up in a pinch without pads. Cheap, thick, and available is a great combination for a consumable like race pads.

There are people out there 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 or titanium pistons, period. There is a reason for this: they work 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. Don’t fight it, just accept it.

While the most aftermarket calipers uses a pressed aluminum piston, the CP8350 uses an expensive machined stainless steel piston. As discussed above, this is to slow and repel the influx of heat into the brake fluid.

Anti-knockbacl Springs
Not only are the pistons stainless steel, they are 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 caliper is less prone to movement because it is attached to the more rigid upright. 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 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 pushes 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.

The downside to springs is that they create slightly more drag by continually exerting force on pistons towards the disc. That said, we’re talking about a 4 lb. spring. The miniscule amount of additional pad and disc wear you’ll see is more than a fair tradeoff for making sure your brake pedal is there and firm when you need it most. Having confidence is crucial while clicking off hot laps.

Integrated Hydraulic Protection
On the CP8350 the bleed screws and crossover pipe are hidden in little coves that protect them from contact. If you frequently pull your wheels on and off your car, you probably know how easy it is to bump your caliper with then inner barrel of the wheel. How easy would it be to ruin your weekend if you happened to knock off a bleed screw and kill your caliper? The integrated protection on the CP8350 will prevent anxiety the next time your friend is putting your wheel back on and you hear that dreaded ‘clunk.’

Also, there’s no need to worry about access to the bleed screws. Fitting a box end wrench on the bleed screw when bleeding isn’t an issue.

High Temperature, Low Drag Seals without dust boots
Dust boots and the track just don't mix very well

Most aftermarket calipers are designed for year round road use and as such come with a bellows style external dust seal. “So?” You ask. Well, we’ve seen them burn up in a single 20 minute session, and all they do is make a big mess. They usually look something like the above pics before and after track use.

Additionally, the OEM caliper seals aren’t designed to handle repeated trips to several hundred degrees without becoming brittle and leaking, etc. On the other hand, the CP8350 caliper has the exact same AP Racing high temperature seals used in NASCAR Sprint Cup, ALMS, DTM, etc. They are designed to operate at extreme temperatures without leaking, and require less frequent replacement and servicing. You won’t see a ragged mess here.

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 CP8350. No more fiddling with a hammer, punch, and pliers, and no tinkering with that annoying spring clip. AP’s bridge bolt pops 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.

Pistons Sized Specifically for the C5 Corvette

The piston sizes for our system were specifically chosen for the Corvette and move about 3% bias to the rear. This will help keep the car balanced on track since most OE systems are designed with significant front bias. Our front system can be bolted to an otherwise stock brake system with no ill-effects, negative impact on ABS, etc. The vehicles stock master cylinder can remain, as can the OEM rear brake system.

Compact, Ultra-lightweight Package

Our brake system follows a simple philosophy: Anything larger than necessary to get the job done is simply dead weight to drag around. 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 size wheels on the track, or the smallest, lightest wheel they can find. Not only is saving unsprung weight critical, R compound tire 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. Our brake system easily clears many of the OEM Corvette wheel options. We have verified that it will clear OEM C5 Z06 17" wheels without a spacer, as well as 18" OEM C5 Z06 rear wheels when run on front.

If you’re worried about the loss of stiffness due to mass reduction, don’t. AP’s CP8350 is an extremely stiff, forged design, and the pedal feels rock hard on the Corvette.

We saved some of the best news about the CP8350 caliper for last.

Approximate front caliper weights vs. C5:

Sprint four piston caliper and bracket= 5.8 lbs.

OEM C5 caliper and bracket= 10.1 lbs.

Caliper weight difference= 4.3 lbs.

That’s four lbs. less unsprung weight per corner to drag around. As mentioned above, the pads retain nearly the same mass as the OEM shape due to their added thickness. For the competitive individual, weight savings often becomes the holy grail of modifications. A lighter car means greater acceleration, superior handling, and less mass to bring to a halt. At some point reducing weight becomes extremely expensive on a dollar per pound basis. When viewed in this manner, our system becomes an even greater bargain.

Essex is AP Racing's official North American caliper reconditioning center. We have skilled service technicians rebuilding hundreds of AP Racing calipers each year for the top teams in NASCAR Sprint Cup, ALMS, etc.

Hardness testing: After disassembly your calipers will be Rockwell hardness tested against the standard for that particular caliper type as sold new. This test provides a relative understanding of how much fatigue and stiffness loss your calipers have experienced. Tired calipers lead to pad tapering, increased pad wear, leaky seals, and a loss of pedal firmness, all things you want to avoid. Essex will make a replace or rebuild recommendation based on the results of this test.

Ultrasonic cleaning: After passing the hardness test, your calipers will be placed in an ultrasonic cleaner to remove all dirt, debris, brake fluid, etc. This method produces results that are far superior to what the average racer could accomplish via hand-cleaning.

Inspection and re-assembly: All serviceable parts of the caliper will be inspected and replaced if necessary, including the seals, abutment plates, pistons, and bleed screws.

Cyclical Pressure Testing: After your calipers have been rebuilt, they will be cycled at high and low pressure on a pressure bench to ensure proper functioning. This is important, as certain leaks only show up under specific pressure conditions.

Price: The labor price to rebuild a CP8350 is $78 per caliper. That does not include parts. Assuming there has been no damage to the caliper, Essex typically recommends replacing the seals ($40) and bleed screws ($15) during the standard reconditioning process. For roughly $125, you can have a fresh, professionally serviced caliper in peak operating condition.

Discs- AP Racing CP3908 Heavy Duty J Hook Racing

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 discsussed 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.

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 2024-T351 heat-treated billet aluminum, with an 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.

Vane Desgin
Notice the huge difference in size between the inlet ports on the inside of these discs.

The internal vane design on AP’s CP3908 is quite a bit different vs. OEM-style discs. After extensive CFD and thermal stress analysis, AP designed the Heavy Duty J Hook with 70 curved vanes and a wide 16.5mm air gap to increase airspeed and heat transfer, while reducing deflection and remaining reasonably lightweight. 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 than the OEM disc, while providing less brake fade, reduced judder, and a longer service life.

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.

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 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).

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.

C5 OEM-style disc (the one we weighed was a slightly used DBA disc), 325x32mm= 21.8 lbs.
Our 325x32mm 70 vane Heavy Duty J Hook= 17.6 lbs.
Weight savings on AP Racing disc vs. stock C5 disc= 4.2 lbs.

As with the calipers, the discs in our system offer roughly 4 lbs. of weight savings over the OEM units.

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.

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. 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 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!

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 socket head bolts are a high tensile strength steel. 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.

Brake Ducting
Essex recommends running our system (or any system) with a quality brake duct system. Please note, DO NOT BOLT ANYTHING BETWEEN THE CALIPER BRACKET AND THE SUSPENSION UPRIGHT! Any ears or tabs from a brake duct system bolted between the bracket and the upright will misalign the caliper from its intended orientation, causing potentially serious damage to the entire brake system or car. The bracket should be directly bolted to the upright as intented, with nothing sandwiched between the two.

Summary and Conclusion
Based on everything we’ve learned during development, we believe our system offers our customers the following advantages over the OEM C5 brake system:

Clears OEM C5Z06 17" wheels and 18" rear OEM C5 Z06 wheels without a spacer
Over 8lbs. of unsprung weight reduction from each front corner of the car vs the stock system, or 16+ lbs. of unsprung weight reduction from the car.
Incredible array of inexpensive race pad options at prices that are nearly $100 lower per set than the OEM pad shape. These pads are large/thick enough to handle typical lapping/race sessions
Mitigation of pad knockback due to 4lb. anti-knockback springs in the calipers
Less chance of damaging bleed screws or crossover tubes when changing wheels due to built-in protection
Caliper finish that is more resistant to wear and deterioration
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 (rather than tapping out the pins)
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 them
High airflow, heavy duty AP Racing J Hook brake discs that are over 1lbs. lighter than the OEM units, available at an extremely competitive replacement price ($250 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.


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