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We ship world wide.
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Brake Pads
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Due to operating wear and tear, brake pads are one of the most commonly replaced components in
the brake system. They also happen to have a significant impact on overall brake system gain as
stated back in Chapter 3. Consequently, upgraded pads are one of the most common brake system
modifications.
However, in this context the word upgrade must be used with great care. While your local auto
supply store likely offers a combination of premium, high-performance, heavy-duty, and severe-use
brake pads, there are no industry standards for what constitutes a premium, high-performance,
heavy-duty, or severe-use brake pad.
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Brake pad advertising is not bound by
NHTSA regulations, and unfortunately
there’s only so much you can find out
by looking at the parts in the box. They
essentially all look the same to the
untrained eye. Consequently, when
picking out a brake pad for your
application, it pays to do a little
research first. (Randall Shafer)
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The same lack of formal definition applies to semi-metallic, non-asbestos organic, ceramic, and
other exotic brake pad chemistries. In all of these cases, the manufacturer is free to call the pads
by whatever name they see fit. Consequently, brake pad selection is a bit of a black art.
Okay, so there’s a lot of black art involved, but that should not discourage you from trying to find
the best brake pads for your vehicle. Good materials are out there, but be forewarned that finding
the best pads for your application can sometimes involve some trial and error. Therefore, you need
to do some homework to determine if the four pieces of friction material inside the cardboard box
are suitable for your application, because the descriptions printed on the outside of the box are not
very helpful at all.
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Brake Pad Terminology
Before going any farther, it’s time to define the nine critical features of a typical brake pad. That’s
right—in some applications, there are no less than nine brake pad design features that can impact
its overall performance.
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Friction Materials
The brake pad friction material is the primary wear element for the brake system. Sometimes called
the friction puck, this sacrificial component is the only part of the brake pad that’s designed to make
contact with the rotor, converting kinetic energy into heat. As a result, over time it’s slowly worn
away until it needs replacing.
Of all the brake pad components discussed, the friction material is arguably the most critical from a
high-performance perspective. There are countless varieties of friction materials available in the
marketplace, and the paragraphs that follow provide you with the information you need to navigate
through the overwhelming number of choices.
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What differentiates one brake pad
from another is the physical
composition of its friction material. Like
a fine suit, high-performance friction
materials are custom-tailored to each
application with a unique blend of
ingredients. (Randall Shafer)
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Wear Sensors
Because all friction materials eventually wear out, a wear sensor is typically fitted to each pair of
brake pads to inform the driver that replacement is required. Although electronic sensors are found
on a few high-end European applications, in most cases a simple steel spring is riveted to the brake
pad backing plate to serve this purpose.
When the friction material wears to the point that replacement is necessary, the spring will contact
the rotor, emitting a high-pitched squeal. This audible signal should not be ignored, for if the friction
material wears completely away, the rotor, caliper, or both may be susceptible to permanent
damage.
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In some applications, a sensor is
placed on the brake pad to alert the
driver if the friction material is worn to
its minimum thickness. While a spring
on the backing plate can be used to
emit an audible squeal under these
conditions, the electronic sensor
shown here informs the driver with a
lamp on the instrument panel. (Randall
Shafer/StopTech)
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Backing Plates
Usually fabricated from simple low-carbon steel, the brake pad backing plate distributes forces from
the caliper pistons to the friction material. Serrated features or through-holes in the backing plate
can also serve to anchor and locate the friction material against the rotor and to transfer the brake
pad friction force from the friction material to the caliper body.
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The responsibility of the backing plates
(red) is to transmit the force from the
caliper pistons to the friction material.
They may also contain retention
features such as holes or serrated
edges to provide a better anchor point
for the friction material. (StopTech)
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Thermal Barriers
Because of their steel construction, the backing plates generally do not insulate the caliper pistons
from heat very effectively. Therefore, in many racing or high-performance applications a thermal
barrier is found sandwiched between the friction material and the backing plate.
The two most common forms of insulator are the ceramic puck and the woven mat. In either case,
the insulating material is bonded or riveted in place during the manufacturing process and cannot
be added on later.
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In order to reduce heat flow from the
rotor to the brake fluid, a piece of
insulating material can be placed
between the backing plate and the
caliper pistons. Stainless steel shims
are the most common thermal barriers
used in OEM applications and can also
help to reduce certain noise
frequencies. (Randall Shafer)
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Adhesives
As the name implies, the brake pad adhesive bonds the friction material to the backing plate. While
historically friction material has been held to backing plates with mechanical rivets, these
high-temperature, high-strength glues are now the norm.
As you can image, selecting the proper adhesive is critical, considering a failure of the adhesive
results in the friction material falling off of the backing plate. In this regard not all adhesives are
created equal, and low-grade adhesives have been known to break down and de-bond in
severe-duty applications.
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Shims
Shims are usually thin stainless steel plates attached to the back side of the brake pad backing
plate. They may also contain a thin layer of damping material (rubber in some cases) sandwiched
between multiple stainless steel plates, but in any case these devices are used to damp out noises
(squealing) that may be generated by the brake pad during use.
Note that the presence of shims does not necessarily guarantee noise-free performance, but in
many applications they certainly help a great deal. A beneficial side effect is that stainless steel
shims can serve as an effective thermal barrier as well. For even better thermal insulation shims
can be fabricated from titanium, but the cost of this material can be prohibitive.
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In racing applications, extreme
measures are taken to keep heat out
of the brake fluid. The shims shown
above are fabricated from titanium, an
excellent thermal insulator.
Unfortunately, the cost of this material
makes it impractical for production
vehicles. (Randall Shafer/StopTech)
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Lubricants
Lubricants can serve two purposes. The first is to allow free motion between the brake pad and its
mounts, or caliper abutment plates. This prevents binding and/or residual drag during use. This is
generally a good thing.
In other applications, lubricant can be applied to the backing plate directly in an attempt to provide
some measure of noise suppression. Frankly speaking, this is semi-effective at best. If this
technique worked as well as some people claim, you would find it in widespread use among the
vehicle manufacturers. It probably doesn’t make matters worse, but don’t expect a tube of goo to
prevent long-term brake noise.
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While advertised as a cure-all for
brake noise, lubricants are really used
to provide free motion between the
backing plate and the caliper locating
features. Too much lubricant can be
detrimental though, as it collects dust,
dirt, and debris over time. (Randall
Shafer)
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Chamfers
Chamfers are sometimes found ground or molded into the leading and trailing edges of the brake
pad friction material itself. By angling the leading edge of the pad, there’s belief that the pad and
rotor are less susceptible to certain noise frequencies. Is there an element of brake voodoo
involved? Certainly, but many, many vehicles come from the factory with chamfers cut into their
pads for just this reason.
The downside is that the chamfers wear down with use and may lose their effectiveness over time.
In the end, every application is once again different and simply having chamfers does not
guarantee noise-free operation across the board.
Noise concerns aside, some high-performance brake pad manufacturers add chamfers to reduce
the initial surface area of the brake pad friction material. This step is taken to increase the rate of
temperature rise when the brakes are first applied, providing a more stable coefficient of friction.
Although the chamfers still wear away as the pads are used, the reduced thermal mass of the
friction material can offset the reduction in chamfer area, enabling rapid temperature rise rates and
consistent performance over the life of the pad.
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In some applications, the leading and
trailing edges of the brake pad friction
material are chamfered. This is
typically a countermeasure for noise,
and does not have an impact on the
brake pad’s performance, although in
theory it contributes to shorter brake
pad life. (Randall Shafer)
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Slots
Slots are nothing more than vertical grooves cut into the face of the friction material. They’re
typically found evenly spaced along the pad, with one or two slots being the most common. While
simple in concept, they serve a variety of purposes.
First and foremost, slots allow an escape route for brake pad dust, preventing it from building up
between the pad and rotor face. Second, slots allow for thermal expansion of the friction puck at
elevated temperatures, which prevents stress cracks in the puck. And finally, slots can act as
redundant leading edges for the puck, which can, in some cases, increase the effective coefficient
of friction of the pad.
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The brake pads shown above have a
rectangular profile (long length, short
height). Consequently, they have two
vertical slots cut in the friction puck to
allow for thermal expansion without
cracking. (Randall Shafer/StopTech)
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Coefficient of Friction
Back in Chapter 3 you learned that the brake pad’s primary role is to convert caliper clamp force
into a frictional force, which opposes the rotation of the spinning rotor as defined by the following
relationship:
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Brake pad friction force (lb) = caliper clamp force (lb) x coefficient of friction (unitless)
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Because most brake pads have a coefficient of friction much less than 1.0, the gain will always be
less than 1:1. More precisely, the coefficient of friction value is always equal to the gain.
Consequently, the friction force is always much less than the caliper clamp force.
So what is the coefficient of friction of your brake pads? Good question! While most brake pad
manufacturers provide you with an approximate value over a typical temperature range, be
forewarned that like a tire’s mu-slip curve, anything and everything can affect the coefficient, and
defining it as a single value is impossible to do.
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Previous | Next
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This has been a sample page from
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High-Performance Brake Systems
Design, Selection, and Installation
by James Walker, Jr.
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High-Performance Brake Systems: Design, Selection, and
Installation gives you the knowledge to upgrade your brakes the
right way the first time. Author James Walker, Jr. doesn’t just tell
you what to do—he uses over 330 photos and plain English to
help you understand how and why your brake system works, what
each of the components does, and how to intelligently upgrade
your brakes for better performance. There are chapters showing
you how to choose and install the most effective rotors, calipers,
pads, and tires for your sports car, muscle car, race car, and
street rod. You will even find special sidebars detailing how each
upgrade will affect your ABS.
Brakes might be one of the most important, yet least understood,
vehicle systems. Brakes are relied upon day in and day out
without giving a second thought to their condition, let alone their
purpose, function, or design. Brake systems can be intimidating,
and they aren’t usually the first thing the average horsepower
junkie chooses to upgrade. But there’s no reason to wait until you
have a problem to learn how your brakes work. Whether you are
a casual enthusiast, a weekend warrior, or a professional racer,
this book will tell you everything you need to know about brakes.
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Click below to view a sample
page from each chapter
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Chap. 1 - Energy Conversion
Chap. 2 - Tires Stop the Car
Chap. 3 - System Design
Chap. 4 - Brake Balance
Chap. 5 - Pedal & Master Cyl
Chap. 6 - Brake Fluid
Chap. 7 - Lines and Hoses
Chap. 8 - Brake Calipers
Chap. 9 - Brake Pads
Chap. 10 - Brake Rotors
Chap. 11 - Sports Car Brakes
Chap. 12 - Race Car Brakes
Chap. 13 - Muscle Car Brakes
Chap. 14 - Street Rod Brakes
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8-1/2 x 11"
Softbound
144 pages
330+ color photos
Item: SA126
Price: $21.95
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Click here to buy now!
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This is a great book that any performance enthusiast will love!
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Chassis Engineering
Precise and predictable handling the key to high performance
driving. The art and science of engineering a chassis can be
difficult to comprehend, let alone apply. In this book, chassis
expert Herb Adams clearly explains the complex principles of
suspension geometry and chassis design in terms the novice
can easily understand and apply to any project. Hundreds of
photos and illustrations offer the information on what it takes to
design, build and tune the ultimate chassis for maximum
cornering power, both on and off the track.
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Price:
$18.95
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The Street Rodders Chassis & Suspension Handbook
The experts at Street Rodder have now compiled a
comprehensive handbook on one of the most critical areas of
street rodding – the chassis. Sections covered in this book
include frame design and construction, hanging suspension
components, independent verses sold front suspensions,
independent verses solid rear axles, steering system design
and modification, driveshafts, brakes, shocks, springs and
much more. The information is this book will give you the
knowledge to properly design and build your chassis and
suspension.
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Price:
$18.95
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How to Make Your Car Handle
Make your car handle, design a suspension system, or just
learn about the chassis; you’ll find what you’re looking for in this
book. Basic suspension theory is thoroughly covered including
roll center, roll axis, camber change, bump steer, anti-dive, ride
rate, ride balance and more. How to choose, install and modify
suspension hardware for best handling; springs, sway bars,
shock absorbers, bushings, tires and wheels. Regardless of the
basic layout of your car it’s covered in this book.
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Price:
$18.95
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The Metal Fabricators Handbook
How to build structurally sound, good looking metal parts for
custom street rods, race cars or restorations. Over 350 step-
by-step photos and instructions illustrate proper welding, metal
shaping and design techniques. Learn to fabricate metal like a
professional. This book is for the reader who already has more
than a passing interest in automotive fabrication. Master metal
craftsman Ron Fournier shares the tips, techniques and
secrets necessary for fabricating metal components for race,
custom or restoration use.
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Price:
$18.95
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Turbo High Performance Turbocharger Systems
This book is the most detailed and up-to-date resource on
turbocharging. You'll learn how turbochargers work, how to
choose the right turbo or turbos for your engine by reading
flow maps, and how to tune your engine to run perfectly with
your turbo system. Uses more than 300 photos and technical
information to help you make more horsepower. It also
discusses the various components of a turbocharger and
explains how to decode turbocharger model numbers,
compressor maps, other specifications and includes a
complete step-by-step turbocharger tear-down and rebuild.
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Price:
$22.95
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Payment, Shipping & Sales
Tax: Iowa
residents must pay 7% sales tax. Items usually ship
within one
business day of receipt of payment! Standard shipping is a flat rate of
$4.95 to
anywhere in the United States with USPS Media Mail.
Priority Mail shipping is available for an
additional $2.95, or
$7.90 for shipping. Shipping is combined and discounted for multiple item
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$1.95 for each additional item. For
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charge! We offer world wide shipping and ship to Canada and Mexico
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International for $11.95, and to most
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America for
$14.95. Satisfaction is Guaranteed. Our store has a NO HASSLE RETURN
POLICY
within 7 days of purchase.
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