Chevrolet Light Duty Truck 1973, Service Manual

Page: 270 / 979

5 -4 BRAKES
Fig. 3--Rear Drum Brake
Fig. 2--Front Disc Brake
THEORY OF
Brakes are simply a means of applying friction to either
stop, slow down or hold an element. Brakes accomplish
their job by converting motion energy, or kinetic energy,
to heat energy, through brake shoes and linings.
On the present day vehicle, the brake shoes are metal
with heat resistant linings attached. The brake shoes are
applied against the brake drum or disc by hydraulic
pressure.
To perform properly, the brake components must be
properly installed and adjusted.
First, the drum or disc must be the right size and shape,
diameter, width, thickness and contour to provide
enough friction area and adequate heat dissipation.
Second, the linings must be of the correct material, size
and contour to provide the proper amount of friction
for:
a. Proper performance
b. Satisfactory durability
c. Freedom from noise and scoring
Third, clearances must be correct.
Fourth, the operating system must be simple, dependable
and easily adjusted.
HYDRAULIC SYSTEM (Fig. 4)
When fluid is contained in a closed system and pressure
is applied to it, the pressure is exerted equally in all
directions (Pascal’s Law). By applying this law, we are
able to have a brake system that is easy to maintain and
functionally stable.
OPERATION
The basic hydraulic brake system consists of (1) a master
cylinder, in which the hydraulic pressure is developed,
(
2
) a cylinder at each wheel, where hydraulic pressure is
utilized to force linings to rub against a brake disc or
brake drum, and (3) the necessary tubing and flexible
hoses to connect the master cylinder to the wheels. Of
course, we need a method of generating this hydraulic
pressure so we have a pedal mounted within the vehicle
and connected to the master cylinder through a push rod.
The principle of hydraulic pressure is put to work
through the use of the pedal.
When the pedal is depressed the master cylinder piston
LIGHT DUTY TRUCK SERVICE MANUAL