Page M-1
Repair and Service Manual
B
B
MECHANICAL BRAKES
Read all of Section B and this section before attempting any procedure. Pay particular attention to Notices, Cautions, Warnings and Dangers.
Fig. 1 Mechanical Brake System
BRAKE SYSTEM OVERVIEW
General Description
This vehicle is equipped with a mechanically activated
rear drum brake system. The brake system consists of a
service brake and parking brake pedal, parking brake
release linkage, equalizer link, brake cables and self
adjusting wheel brake assemblies (Ref. Fig. 1).
Although the brake system is similar to an automobile, it
is
different in important ways
. The system operates in
a very severe environment. Fertilizer, dust, grass clip-
pings, tree roots and other objects can cause corrosion
and physical damage to the brake components. Unlike
automotive hydraulic brakes, mechanical brakes depend
on the travel of the brake cables to move the brake
shoes against the brake drums. The travel of the brake
cables is governed by the brake pedal. If the cables can-
not travel far enough to absorb the slack (free travel) in
the system and still apply the shoes to the drums, the
braking effort at the wheel brake will not be adequate.
The self adjusting mechanism in the wheel brakes
requires enough cable travel at the wheel brake to work
reliably. When the brake is released, there must be slack
in the system so the brakes will release fully and the
adjusters will function. Free pedal travel, pedal force,
shoe to drum clearance and braking capability are
closely related. It is very important to maintain the
proper relationships to assure braking performance and
the best wheel brake adjustment.
How the Service Brake Works
Depressing the service brake pedal pulls the equalizer
link, which is connected to the brake cables (Ref. Fig. 1).
The first part of the pedal travel removes slack from the
Brake Cables
Retaining
Ring
Cotter Pin
Clevis Pin
Brake Lever
Self Adjusting
Wheel Brake
Spherical Nut
Jam Nut
Brake Pedal Pivot Bolt
Compensator
Assembly
Pedal
Latch
Arm
Kick Off
Cam
Torsion Springs
Washers
Bushing
Cam
Pivot
Spacer
Torsion
Spring
Cap Screw
Set
Screw
Pedal Bumper
Nylock Nut
Identification
Hole*
Parking Brake Pedal
Catch Bracket
Part of Frame
Parking Brake
Release Linkage
Part of
Accelerator Pedal
Push Nut
Hinge Pin
Service
Brake Pedal
Lock Nut
Brake Pedal
Bushing
Equalizer
Link
Summary of Contents for EXPRESS L4
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