BRAKE COMPONENT BRAKING SYSTEMS

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Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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2009Pearson
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OBJECTIVES:
After studying Chapter 67, the reader should be
able to:

•
•
•
•
•

Prepare for ASE Brakes (A5) certification test.

List the parts and terms for disc and drum
brakes.
Describe brake design requirements.
List the six brake system categories.
Discuss federal braking and stopping
standards.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
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KEY TERMS:
adjustable pedals • antilock braking system (ABS) • apply
system
base brakes • boost system • brake balance control

system • brake pedal • brake warning lights
Department of Transportation (DOT) • disc brakes • drum
brakes
electric adjustable pedals (EAP)
Federal Motor Vehicle Safety Standards (FMVSS) •
foundation brakes
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
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KEY TERMS:
gross vehicle weight rating (GVWR)
hydraulic system
lightly loaded vehicle weight (LLVW)
parking brake

red brake warning lamp
service brakes • snub • wheel brakes

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
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Brakes are by far the most important mechanism on
any vehicle because the safety and lives of those
riding in the vehicle depend on proper operation
of the braking system.
It has been estimated that the brakes on the average
vehicle are applied 50,000 times a year!

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition

By James D. Halderman

©©2008
2009Pearson
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HOW BRAKES STOP VEHICLES
Brakes are an energy-absorbing mechanism that converts vehicle
movement into heat while stopping the rotation of the wheels.
All braking systems are designed to reduce the speed and stop a
moving vehicle and to keep it from moving if the vehicle is
stationary.
Service brakes are the main driver-operated brakes of the
vehicle, and are also called base brakes or foundation brakes.
See Figure 67–1.

Continued

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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Figure 67–1 Typical vehicle brake system showing all typical components.

Continued

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
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Most vehicles built since the late 1920s use a brake on each wheel.
To stop a wheel, the driver exerts a force on a brake pedal. Force on
the brake pedal pressurizes brake fluid in a master cylinder.
This hydraulic force (liquid under pressure) is transferred through
steel lines and flexible brake lines to a wheel cylinder or caliper at
each wheel. Hydraulic pressure to each wheel cylinder or caliper is
used to force friction materials against the brake drum or rotor.
The heavier the vehicle and the higher the speed, the more heat the
brakes have to be able to absorb. Long, steep hills can cause the
brakes to overheat, reducing the friction necessary to slow and stop a
vehicle.
See Figures 67–2 and 67–3.
Continued

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008

2009Pearson
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Figure 67–3 When driving down long,steep
grades, select a lower transmission gear to
allow the engine compression to help
maintain vehicle speed.

Figure 67–2 Brakes change the energy of
the moving vehicle into heat. Too much
heat and brakes fail, as indicated on this
sign coming down from Pike’s Peak in
Colorado at 14,000 ft (4,300 m).

Continued

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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2009Pearson
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DRUM BRAKES
Drum brakes are used on the rear of many rear-wheel-drive,
front-wheel-drive, and four-wheel-drive vehicles.
When drum brakes are applied, brake shoes are moved outward
against a rotating brake drum. The wheel studs for the wheels are
attached to the drum. When the drum slows and stops, the wheels
also slow and stop.
Drum brakes are economical to manufacture, service, and repair.
Parts are readily available and reasonably priced. On some
vehicles, an additional drum brake is used as a parking brake on
vehicles equipped with rear disc brakes.
See Figures 67–4 and 67–5.
Continued

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
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Figure 67–4 Typical drum brake assembly.

Continued

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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2009Pearson
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Figure 67–5 Drum brake assembly as used on the right rear wheel.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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2009Pearson
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DISC BRAKES
Disc brakes are used on the front of most vehicles built since the
early 1970s and on the rear wheels of many vehicles.
A disc brake operates by
squeezing brake pads on
both sides of a rotor or
disc that is attached to
the wheel.
Figure 67–6
Typical disc brake assembly.

Due to the friction between
the road surface and the
tires, the vehicle stops.
Continued

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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BRAKE DESIGN REQUIREMENTS
To summarize, events necessary to stop a vehicle include:
1. The driver presses on the brake pedal.
2. The brake pedal force is transferred hydraulically to a wheel
cylinder or caliper at each wheel.
3. Hydraulic pressure inside the wheel cylinder or caliper presses
friction materials (brake shoes or pads) against rotating brake
drums or rotors.
4. The friction slows and stops the drum or rotor. Since the drum
or rotor is bolted to the wheel of the vehicle, the wheel also
stops.
5. When the wheels of the vehicle slow and stop, the tires must
have friction (traction) with the road to stop the vehicle.
Continued

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
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All braking forces must provide for the following:
1. Equal forces must be applied to both the left and right sides of
the vehicle to assure straight stops.
2. Hydraulic systems must be properly engineered and serviced
to provide for changes as vehicle weight shifts forward during
braking.
Hydraulic valves must be incorporated into the hydraulic
system to permit the maximum possible braking forces but
still prevent undesirable wheel lockup.
Antilock braking systems (ABS) are specifically designed to
prevent wheel lockup under all driving conditions, including
wet or icy road conditions.
Continued

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
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3. The hydraulic system must use a fluid that will not evaporate
or freeze. The fluid has to withstand extreme temperatures
without boiling and must not damage rubber or metal parts of
the braking system.
4. The friction material (braking lining or brake pads) must be
designed to provide adequate friction between the stationary
axles and the rotating drum or rotor. The friction material
should be environmentally safe. Nonasbestos lining is
considered to be safe for the environment and the technician.
5. The design of the braking system should secure the brake
lining solidly to prevent the movement of the friction
material during braking.
Continued

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
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6. Most braking systems incorporate a power assist unit that
reduces driver effort but does not reduce stopping distance.
Vacuum from the intake manifold is the most commonly used
source of vacuum for power brake boosters. The engine itself
must be functioning correctly for proper operation of the
power vacuum booster.

NOTE: It is this movement of the friction material that causes brake

noise (squeal). Various movement dampers are used by the vehicle
manufacturers to help control any movement that does occur. It is

important that every technician restore the operation of all aspects of the
braking system whenever they are serviced, even the noise dampers.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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2009Pearson
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BRAKE SYSTEM CATEGORIES

Brake system components
can be classified into six
subsystem categories,
depending on function.

Figure 67–7

Typical brake system components.
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

Continued

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Apply System Driver starts operation of the system by pressing the
brake pedal or applying the parking brake. The apply system
includes all levers, pedals, or linkage needed.
Boost System Used on most vehicles to increase brake pedal force.
Hydraulic System Brake pedal force is transferred to the hydraulic
system, where force is directed to the wheel brakes.
Wheel Brakes Hydraulic pressure moves a piston, in a disc or
drum brake system, that uses friction to press material against a

rotating drum or rotor. Resulting friction slows wheel rotation.

Continued

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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2009Pearson
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Brake Balance Control System Mechanical, electrical, and
hydraulic components ensure brakes are applied quickly,with
balanced pressure for safe operation. Components include
metering valves, proportioning valves, and antilock braking
system components.
Brake Warning Lights The red brake warning lamp lights
whenever a hydraulic system failure occurs. The amber ABS

warning lamp or dim red brake light indicates an ABS self-test
and/or a possible problem in the ABS system.
See Figures 67–9 and 67–10.

Continued

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

©©2008
2009Pearson
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