Page K-2
Repair and Service Manual
B
MECHANICAL BRAKES
Read all of Section B and this section before attempting any procedure. Pay particular attention to Notices, Cautions, Warnings and Dangers.
system. Continued motion of the brake pedal pulls both
the left and right brake cables. Each brake cable pulls a
brake lever which pushes the rear brake shoe against
the brake drum. When the rear shoe contacts the brake
drum, it can no longer move rearward. Additional pedal
(and cable) travel causes the actuator bracket (moving
anchor) to move and applies force to the front shoe,
pushing it against the brake drum. The force applied to
the front and rear shoes is approximately equal. As the
shoes contact the moving brake drum, the shoes try to
move in the direction of drum rotation. This movement
results in the typical brake shoe wear patterns.
Equalizer Link
The equalizer link balances braking between the driver
and passenger sides of the vehicle. Variations in wheel
brake adjustment, cable friction and manufacturing toler-
ances may cause the equalizer to be slightly misaligned.
This misalignment is normal.
Automatic Adjuster Mechanism
Never manually adjust the brakes at the star wheel. Doing
so will cause permanent damage to the adjuster assem-
bly and result in a gradual loss of brakes.
The wheel brakes are equipped with an automatic
adjuster mechanism that is designed to compensate for
brake shoe wear and eliminate the need for manual
brake shoe adjustment. Do not manually adjust the
brakes by prying back the adjuster arm and turning the
star wheel. Permanent damage to adjuster will result.
Adjustment takes place only when the brake is fully
applied and released
while the vehicle is moving
(Ref.
Fig. 2). It is very important that the brake cables permit
the brake levers to release fully when the brake pedal is
in the released position.
How the Parking Brake Works
The parking brake is operated by a smaller pedal which
extends across the top of the service brake pedal. It is
attached to the service brake pedal with a hinge pin and
is spring loaded (Ref. Fig. 3).
A
C
Brakes adjust only while the vehicle is moving.
When the brake pedal is depressed, the brake lever
moves toward the front of the vehicle (A).
The other end of the brake lever moves to the rear of
the vehicle (B) where it contacts the brake adjuster
arm, causing it to move.
The brake adjuster arm moves away from the star
wheel (C). The amount of adjuster travel is limited by
the amount of brake shoe travel required to contact
the brake drum. The amount of travel increases as the
brake shoe lining wears.
When the brake pedal is released, the adjuster spring
retracts the brake adjuster arm which contacts the star
wheel. Note that adjustment only takes place when the
brake pedal is released while the vehicle is in motion.
If the brake shoes have worn far enough to permit the
brake adjuster arm to contact the next tooth of the star
wheel, the star wheel will be advanced by the tension
applied to the adjuster arm by the adjuster spring.
If the brake shoes have not worn enough to permit the
brake adjuster arm to contact the next tooth of the star
wheel, the brake adjuster arm will move on the flat of
the star wheel. The star wheel does not rotate and no
adjustment occurs.
Brake Adjuster Arm
Star Wheel
Adjusting Screw
Adjuster Spring
Brake
Shoe
B
Fig. 2 Wheel Brake Adjustment
Содержание EXPRESS L6 2012
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