mechanical linkage that works the rear wheel brakes
(fig. 3-42, view B).
HYDRAULIC BRAKE SYSTEM
A hydraulic brake system is primarily a liquid
connection or coupling between the brake pedal and the
individual brake shoes and drums, as shown in figure
3-43. The system consists of one master cylinder
connected by pipes and flexible tubing to the wheel
cylinders. The wheel cylinders control the movement of
the brake shoes at each wheel. When the brake pedal is
depressed, the hydraulic fluid forces the pistons in the
wheel cylinder against the brake shoes, forcing the shoes
against the brake drum or brake discs stopping the
Hydraulic brakes are self-equalizing brakes. If the
actuating pistons were all the same size, each brake in
the hydraulic system would receive an identical
hydraulic force when the brakes were applied, because
a force exerted at any point upon a closed liquid is
distributed equally through the liquid in all directions at
the same time. All brake systems have larger wheel
cylinders in the front than in the rear. When you stop a
vehicle, more weight is automatically shifted forward
due to inertia, so more front-wheel braking is required.
The master cylinder is a reservoir for the brake fluid
and contains pistons and valves which change
mechanical force to hydraulic pressure when the brake
pedal is depressed, as shown in figure 3-43. The pressure
on the brake pedal moves the piston within the master
cylinder to force the brake fluid from the master cylinder
through tubing and flexible hoses to the wheel cylinders.
As pressure on the pedal is increased, greater hydraulic
pressure is built up within the brake cylinders, and thus
greater force is exerted against the ends of the brake
shoes. When pressure on the pedal is released, the
retracting springs on the brake shoes return the wheel
cylinder pistons to their released positions. This action
forces the brake fluid back through the flexible hose and
tubing to the master cylinder.
Figure 3-42.-Parking brake configurations.
Figure 3-43.-Hydraulic brake system.