|
| |
|
| |
Buy with confidence!
If for any reason
you're not
completely satisfied
with an item, simply
return it within 7
days and the
purchase price will
be refunded.
|
|
|
|
| |
|
| |
We ship world wide.
All international
orders must be paid
online. Checks or
money orders drawn
on non-US banks will
not be accepted.
|
|
|
|
|
|
Tires Stop the Car
|
|
|
As you just learned in Chapter 1, brakes do not stop the car—they simply convert energy from one
form into another. The responsibility of stopping the car falls solely on the tires, or more specifically
the tire-to-road interface. Only these four palm-sized patches of rubber that are in contact with the
road below (the contact patches) govern how quickly a car will stop.
Of course, a poorly designed or malfunctioning brake system can certainly prevent a vehicle from
achieving its maximum deceleration rate, but the best stopping performance each and every time is
dictated by the tire-to-road interface. A few simple equations are used later in this chapter to
illustrate this point, but for the next few pages sit back and hang tight. It’s now time to talk about
another law.
|
|
|
 |
|
|
|
The brakes don’t stop the car—that’s
the tires’ job! For this reason, tires
come in a wide variety of shapes,
sizes, and designs to optimize the
available brake force. The lack of a
tread pattern on this tire makes it a
poor choice for wet-weather
performance, but a great choice for
racing when the track is dry. (Hoosier
Racing Tire)
|
|
|
|
The First Law of Motion
You may recognize Sir Isaac Newton as the guy who allegedly defined the concept of gravity when
an apple fell on his head one afternoon. However, for a few paragraphs you should look past that
rather major accomplishment and focus on the first of his three stated Laws of Motion.
(Note that Newton’s First Law of Motion is not to be confused with the First Law of Thermodynamics
from Chapter 1. Apparently, every physicist wants to be known for discovering the first law of
something or other.)
Paraphrasing Newton with a reasonable degree of accuracy, the First Law of Motion states that an
object at rest will stay at rest unless it is acted upon by an external force. Conversely, it also states
that an object in motion will stay in motion unless it too is acted upon by an external force. In other
words, things sitting still will just sit still until you push them and things that are moving continue to
move until you do something to stop them.
|
|
|
Brake Forces
Applying Newton’s First Law of Motion to vehicle brake systems is relatively straightforward. It goes
something like this: Once in motion, a vehicle essentially will not slow down or stop unless it is acted
upon by an external force, or what can now be called a brake force.
So where do these brake forces come from? Essentially, they result from any mechanism that
absorbs a vehicle’s kinetic energy (they are one and the same). Consequently, this merits a brief
revisit of energy transformation factors from Chapter 1, now adding in the resulting brake force
contributions for each mechanism:
|
|
|
1. Rolling resistance brake forces result from the body and tread of the tire resisting
deformation at the contact patch. As the tire flattens out against the road, a force is generated
that resists the motion of the vehicle.
2. Axle, differential, bearing, and engine brake forces result from rotating and reciprocating
friction. As these components mesh and rub together, they resist any motion between
themselves, which is then mechanically transferred to the tire-to-road interface.
3. Aerodynamic brake forces result from the vehicle simply traveling through the air. As the
vehicle attempts to push the air out of its path, the air molecules react by resisting the motion.
In other words, the air is not happy with the situation and it pushes back (the sensation you get
from holding your hand out of the car window).
4. Mechanical deformation brake forces result from running the vehicle into a fixed object.
Again, this is a highly undesirable, yet highly effective, way of stopping a vehicle. Turn 3 at
Martinsville pushes back pretty hard, as do trees and telephone poles.
So, while it is nice to be aware of these secondary brake force mechanisms, the whole point of
this book is to understand the contribution of the brake system components. Consequently,
the rest of this chapter leaves these factors behind and focuses on brake forces occurring at
the tire-to-road interface as a result of brake system operation.
|
|
|
 |
|
|
|
Brake forces can come from a variety
of sources other than the brake
system. For example, if a mischievous
co-driver were to force a car traveling
at highway speeds into first gear, the
resulting driveline friction forces would
be transmitted immediately back to the
driven wheels. Not that we speak from
experience here…
|
|
|
|
|
|
Tire Slip
Tire slip, or simply slip, is the single most important concept in understanding any aspect of vehicle
performance (at least in my humble opinion). Without slip, vehicles could neither accelerate, nor
decelerate, nor turn, as a tire can only generate force when it is slipping. As you’ll learn in a few
moments, a tire that is not slipping is free rolling, or coasting, and a free-rolling tire does not
generate any force at all (except for the small amount of brake force due to its internal rolling
resistance).
Before going any further, let’s clarify one important point: A tire does not need to be spinning wildly
or skidding out of control to be slipping. Although these conditions are a result of a significant
amount of slip, there are many other times where a slipping tire does not actually look like it’s
slipping at all. Yet for all practical purposes, any time your vehicle is in motion, its tires are slipping,
even though you can’t see it with the naked eye.
|
|
|
Applying this concept to brake system performance is relatively straightforward. In order for a tire to
generate a brake force, it must be slipping relative to the road surface in the direction of travel
(normally to a very small level, but it is slipping nonetheless). If a tire is not slipping, it is not
generating any brake force (again, ignoring the brake force due to its internal rolling resistance).
Although that may sound odd, it makes more sense by taking a moment to formally define slip. Tire
slip can be quantified mathematically by the following equation:
|
|
|
Tire slip (%) = (1 – {speed of the tire (mph) ÷ speed of the vehicle (mph)}) x 100
|
|
|
|
What this implies is that in order for a tire to generate brake force, it must be spinning more slowly
than the speed of the vehicle would suggest. However, looking at this relationship in tabular format
is somewhat easier on the eyes. For this reason, make your way over the tire slip sidebar for a
different look at this slightly perplexing situation.
|
|
|
 |
|
Different surface textures,
environmental conditions, and slip
levels can influence the brake force
contribution from the adhesive,
deformation, and the mechanical wear
modes of friction. For example, water
on the road surface partially separates
the tire from the road, greatly reducing
the available adhesive friction. This
results in extended stopping distances.
(Wayne Flynn/pdxsports.com)
|
|
|
|
|
|
Tire Slip Calculations
The data in the table below illustrates how much tire slip would be present for given combinations of
tire speed and vehicle speed.
|
|
|
Tire speed Vehicle speed Tire slip
|
|
|
|
Condition 1 50 mph 50 mph 0%
Condition 2 45 mph 50 mph 10%
Condition 3 0 mph 50 mph 100%
|
|
|
|
So, what do these numbers mean? Well, a few observations can quickly be made:
1. Condition 1 indicates that when the tire speed (50 mph) is the same as the vehicle speed (50
mph), there is zero slip present. Because this is a free-rolling condition, there is no brake force
present between the tire and the road. The vehicle will be coasting.
2. Condition 2 indicates that when the tire slows down (45 mph) relative to the vehicle (50 mph), the
slip level increases (10 percent in this case). This is the slip range where most normal braking
occurs.
3. Condition 3 represents a tire that has stopped spinning (0 mph) although the vehicle continues
to speed along (50 mph), resulting in 100-percent slip. This is the classic ”brakes locked up”
situation, which is usually accompanied by screeching sounds and billowing tire smoke. Note that
this condition is also commonly referred to as sliding or skidding and is generally an undesirable
way to slow down a vehicle.
|
|
|
 |
|
|
|
100 percent tire slip, also known as
wheel lock, occurs if a vehicle is still
moving yet the tire is no longer
rotating. This may be amusing for the
spectators, but it’s not the most
effective way to achieve the best
possible stopping distance. (Wayne
Flynn/pdxsports.com)
|
|
|
|
|
|
How Brake Forces are Generated
So now that you know that slip is required to generate force, how exactly does the slipping tire
generate brake force? As the tire rolls along without slip, there is constant interaction between the
tire and the road, yet with the exception of a small amount of rolling resistance, there are no brake
forces generated. However, as soon as a torque is applied to the tire by the brake system (more to
come in Chapter 3), it wants to slow down.
Unfortunately for the tire, the car does not want to slow down, and consequently the tire is forced to
stretch and distort. This is because there is resistance, or friction, at the tire-to-road interface that
prevents the tire from decelerating as rapidly as it would like. Few things are more fun than getting
a group of contact physicists together in a room and asking them why and how tires generate these
forces, but for now it makes more sense to break it down into simple, bite-sized pieces.
|
|
|
Adhesive Effects
Any time two objects in nature come in contact with one another, there are momentary electrostatic
bonds formed between them. In other words, to some extent they want to stick together. One of the
best practical examples is that of garden-variety duct tape. The adhesive characteristics of the tape
allow it to effectively stick temporarily wherever it is placed.
This same mechanism is in effect as the tire rolls along the road. During braking, the contact patch
is continuously forming adhesive bonds with the road surface below, which resist the tire’s desire to
decelerate—after all, if the tire were hanging in mid-air, it would slow down much more quickly when
the brakes were applied. While in this case the adhesive effect may not be as pronounced as it is
with duct tape, the rubber tire will elastically deform, and consequently slip, when brake torque is
applied. The force of the electrostatic bonds formed between the tire and the road is the first
component of the total brake force.
|
|
|
 |
|
|
|
Tires used for racing in the rain are
optimized to take maximum advantage
of the deformation effect, since water
on the track greatly reduces the
adhesive effect. The rain tire shown
here uses extremely soft rubber
compounds to enhance deformation,
while large, open channels molded into
the tread face purge water from the
contact patch in an attempt to increase
adhesion. (Hoosier Racing Tire)
|
|
|
|
|
|
 |
|
|
|
Although ABS is designed to prevent
such theatrics, pulling the fuse and
stomping on the brake pedal is an
effective way to force the tires to
achieve 100-percent slip. While this
technique won’t generate the shortest
possible stopping distances, the
resulting skid marks provide evidence
that rubber is physically removed from
the tire under these conditions. (The
Tire Rack)
|
|
|
|
|
|
Previous | Next
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
This has been a sample page from
|
|
|
|
|
 |
|
High-Performance Brake Systems
Design, Selection, and Installation
by James Walker, Jr.
|
|
|
|
|
|
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.
|
|
|
Click below to view a sample
page from each chapter
|
|
|
|
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
|
|
|
|
|
|
8-1/2 x 11"
Softbound
144 pages
330+ color photos
Item: SA126
Price: $21.95
|
|
Click here to buy now!
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
This is a great book that any performance enthusiast will love!
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
Other items you might be interested in
|
|
|
|
|
|
Sport Compact Turbos & Blowers
While most owners of sport compacts can afford the simple bolt-ons
available, some owners want to take their modifications a step further.
There is intense competition to be the fastest, and quite often the only
way to win is to go to the next level – by installing a supercharger /
blower or turbocharger on your engine. This book is an enthusiast’s
guide to understanding and using turbochargers and superchargers
on sport compact cars.
|
|
|
 |
|
|
|
|
|
Price:
$18.95
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Shipping is combined and discounted for multiple item purchases!
Buy more and save on shipping!
We ship Worldwide! See International Shipping for more information!
|
|
|
Search Our Store for More Great Ford, Lincoln & Mercury Items!
|
|
|
FAST AND EFFICIENT SERVICE
We believe customer service and online retail can coexist. Our policy is to treat customers the way
we would like to be to treated. We strive to describe all items correctly. You have many options
online, but we believe our service is the best. We work around the clock to fill orders and ship items
within one business day. It is our goal to serve the customer before, during and after the checkout
process. Why gamble with your money and purchase from other sellers? We look forward to doing
business with you now and in the future.
|
|
|
FAST SHIPPING
Items usually ship within one business day of receipt of payment! We keep large quantities on hand
and have a state of the art inventory management system to ensure your items are in stock and
ready to ship.
|
|
|
YES, WE HAVE A RETURN POLICY
Satisfaction is guaranteed. Our store has a NO HASSLE RETURN POLICY within 7 days of
purchase. Your exchange will be processed upon receipt. If you are not satisfied with your
purchase, our knowledgeable team will do their best to make sure you get what you are looking for.
|
|
|
QUALITY AND AFFORDABILITY
Why pay retail when you can save money and benefit from our purchasing power? We stock large
quantities to get you the best prices and assure the item you order will be in stock and ready to
ship. We have a COMBINED SHIPPING incentive whereby each additional item adds $1.95 to the
s/h. The more you buy, the more you can save!
|
|
|
SHIPPING
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 $3.00, or $7.95 shipping. Shipping is combined
and discounted for multiple items purchases as follows: first item regular price shipping, add $1.95
for each additional item.
INTERNATIONAL SHIPPING
We ship to Canada and Mexico with Priority Mail International for $10.95, and to most locations in
Europe, Australia, Asia, Japan and South America for $14.95. Shipping is combined and discounted
for multiple items purchases as follows: first item regular price shipping, add $1.95 for each
additional item. All international orders must be ordered and paid online, as we can no longer
accept checks or money orders drawn on non-US banks.
|
|
|
PAYMENT & SALES TAX
We accept Paypal, Visa, Mastercard, Checks and Money orders. Paypal is the preferred form of
payment. Our online shopping cart system is powered by PayPal, the most secure way to send
payment online. Iowa residents must add 7% sales tax.
|
|
|
If you have any questions or comments please feel free to contact us. We look forward to serving
you and fulfilling your needs.
|
|
|
Thanks for your business!
|
|
|
MRE
PO Box 47
Grinnell, IA 50112
|
|
|
|
|
|
|
|
