AP Racing BMW E36 M3 Radi-CAL Competition Brake Kit Front CP8350/325mm
If you have a BMW E36 M3, this is the proven front big brake kit, using AP CP8350 4 piston calipers and oversized 325mm x 32mm, 70 directional curved vane two piece rotors.
AP Racing BMW E36 M3 Radi-CAL Competition Brake Kit Front CP8350/325mm Details:
WHAT'S IN THE BOX?
- One pair AP Racing CP8350 racing calipers
- One pair 325x32mm AP Racing CP3908, 70 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.
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 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.
Below is a drawing of the basic pad shape used in the CP8350:
Dimensions= 133.2mm x 60.0mm x 20.0mm
Below are the pad compounds that Essex offers for our CP8350/325mm disc combination. Please note that the pad shape we use in our caliper is available in a variety of radial depths (heights) from different manufacturers. When combined with the CP3908 325x32mm disc, Essex recommends the 50mm radial depth version. Other common radial depths in this pad shape are 43mm and 39mm. Those radial depths will fit into our caliper, but you will be leaving an unswept 'ring' around the disc near the attachment points to the hat (the pad will not hang as low in the caliper). Leaving a portion of the disc face unswept can create a temperature differential across the face of the disc, and doing so could lead to premature disc cracking. That said, we have not run into such a problem with our kits in the field.
Below each manufacturer listed below, the pad compounds are ranked from most aggressive to least aggressive.
- DSUNO (D50)
- DS3000 (D50)
- DS1.11 (D50)
- DS2500 (D50)
- F11R (D42)
- F10R (D42)
- F8R (D42)
Pad Cross Reference
Again, please keep in mind that there are many other compounds available on the market from other manufacturers. Since we do not offer many of the brands listed below, Essex cannot guarantee the fitment of these pads in the AP Racing CP8350 caliper. Based on our research however, we believe that these are the appropriate cross references for the basic shape. However, you should verify with either the manufacturer or your installer prior to purchasing any of them.
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!
While most aftermarket calipers use a pressed aluminum piston, the CP8350 uses an expensive machined stainless steel piston. Aluminum has a much higher thermal conductivity than stainless steel, and therefore transmits heat into your brake fluid much more quickly. That is exactly what you don't want! Stainless steel pistons are far superior to aluminum pistons in creating a thermal barrier. They help keep heat out of your brake fluid, preventing a soft pedal (brake fluid fade) on the track. This has been proven over and over again at all levels of motorsport.
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.
AP Racing High-Temp Piston Seal
Simple Pad Change with One Bolt
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. 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.
Pistons Sized Specifically for Your Car
The piston sizes in our systems are specifically chosen to closely mimic the OEM brake torque on a given axle. As such, our front systems can be bolted to otherwise stock cars with no ill-effects, negative impact on ABS, etc. The vehicles stock master cylinder can remain, as can the OEM rear brake system.
Integrated Bleed Screw and Crossover Tube Protection
How often do you take the wheels on and off of your track car? At least once per event? A 30lb. wheel and tire combo can do quite a bit of damage when it collides with a caliper's bleed screw or crossover tube. Of the hydraulic components shown below, which do you think have better impact protection?
The CP8350's body was designed to protect the bleed screws and crossover piping from heavy-handed crew members and track debris. These delicate hydraulic components reside in small coves on the caliper body that can withstand the impact of a wheel, tool, rock, etc. Wheel, pad, and fluid changes become less worrisome and faster, and less time in the pits equals more time on the track.
Ultra-lightweight, Compact Design
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 CP8350 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 CP8350 calipers are incredibly stiff, and designed from scratch with only the racetrack in mind.
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 (IMSA, SRO, Trans-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.
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.