AP Racing / VAC Competition E30 M3 Brake
You wanted it, we built it! After the success of these systems
on the E36 and E46, we created our own version for the E30 M3...
What a killer setup!
Finally; an affordable system that will handle all the horsepower
you can fit into an E30 chassis and at the full weight of a street
car; all while being light enough for even the most feather weight
E30 M3 race car. ALL the features you want and a brand you trust!
After testing on two prototype configuration E30 M3s that see
constant abuse, the feedback is tremendous. Read more to see all of
the awesome features of these BBKs:
NOTE: For use along with 17" or larger wheels with
antiquate brake clearance, often times, a 10mm spacer may help a
While some E30 M3s have built S14s, more and more have 6 and
even 8 cylinder swaps, turbos and superchargers. These cars are
getting faster and stresses are growing as we continue to help
owners go faster and faster... This kit was developed with a
competition mentality, not to gain points at a car show.
AP has been supplying professional race teams at the highest
levels of motorsport with brake systems and components: They know
what works and what doesn't. Optimization is our focus so we've
assembled our kits with components that are durable, efficient and
light weight. From 20min sprints to 24hr endurance races, our
competition kits are up to whatever you can through at them.
Let’s take a look at how the VAC / AP Racing / Essex competition
brake system for the BMW M3 sets itself apart...
Calipers- AP Racing CP8350 Four Piston
Let's first take a look at the calipers. They are the most
eye-catching piece of the system, and the one most often touted in
marketing material from the manufacturer. ‘Racing inspired’ is the
most common term bandied about, but what does that really mean? In
this case it just means that the caliper is a fixed, opposed piston
caliper with a company logo. Beyond that, there aren’t all that
many similarities between the those calipers and true aftermarket
race calipers. Let’s take a look at some of the design
The first obvious weakness when looking at a standard Brembo or
other aftermarket caliper is the finish. Most aftermarket calipers
come in a painted finish, whether they are red, black, or gold.
This painted finish is for corrosion resistance and appearance.
Unfortunately, for all of the compliments pretty 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 decimation of the finish in a fairly short
period of time.
How many features from the best racing calipers in the world can
you cram into a $500 caliper? Probably more than you ever thought
possible! AP Racing’s CP8350 was designed to be the market leader
in performance and features while maintaining a wallet-friendly
price point. AP’s newest design brings real racing technology like
stainless steel pistons, anti-knockback springs, and integrated
hydraulic protection to the average enthusiast at lower prices than
the competition charges for watered-down street components.
Incredibly, this is achieved while maintaining an unloaded weight
of only 4.8 lbs. The CP8350 completely redefines the content/cost
ratio among aftermarket brake calipers.
This caliper was designed to be ultra-lightweight, stiff, and
durable under all track conditions. The finish we chose is a hard
anodizing. Hard anodizing 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 on the aluminum. 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. They will go from semi-ugly grey, to a semi-ugly
grey-brown (see below). In short, they’ll look like the race
calipers they are. More importantly though, you aren’t going to
have bits of anodizing sticking to the sides of your pistons.
(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
Brake Pads, Thick 20mm (Inexpensive ones
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 BMW calipers are roughly $250, while the average set for
the AP Racing CP8350 costs $175. 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
Also, since this pad shape 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
Brembo style aluminum piston vs. AP Racing machined
stainless steel piston
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.
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 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
Integrated Hydraulic Protection
Pictured above is a set of calipers we pulled from a car we were
testing (Lancer Evo). We saw that the right hand caliper had a bent
crossover pipe. Most likely it was bent when a wheel was being
installed. Or, it could have been hit by a piece of track debris.
Regardless of how it happened, this is precisely the type of damage
the CP8350 was designed to prevent.
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
High Temperature, Low Drag Seals without dust
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.
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 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 BMW M3
The piston sizes for our system were specifically chosen for the
BMW M3 and move a small amount of 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 diameter 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 the OEM 18” option wheels and most
aftermarket 17" wheels. Please feel free to download the wheel
template at the top of this page to verify wheel fitment with your
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 M3.
We saved some of the best news about the CP8350 caliper for
last. With pads, it weighs over three pounds less than the OEM
caliper and that doesn't include the brakcet! All told, we shave
nearly 7lbs per corner. That’s 7lbs. 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
Lifetime Professional Reconditioning
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
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
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
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.
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
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. the OEM 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
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
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.
As with the calipers, the discs in our system offer additional
weight savings over the OEM units. Despite being 4mm wider, the
two-piece AP discs provide a weight reduction of over 1lbs.
unsprung weight per corner!
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
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
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
Stainless Steel Brake Lines
Based on everything we’ve learned during development, we believe
this system offers our customers th
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