Wear Compensation; Parking Brake Operation - Jeep 1979 CJ-5 Technical & Service Manual

BRAKES 26-33
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Fig. 21-22 Drum Brake Assembly—CJ Models
As the primary brakeshoe pivots downward, it exerts
a rearward force on the adjuster screw assembly. Since
the adjuster screw interconnects the lower ends of the
brakeshoes, this additional force is transmitted directly
to the secondary brakeshoe increasing its braking ac-
tion. The additional force applied to the secondary
brakeshoe accounts for the fact that the secondary
brakeshoe linings are generally thicker and have more
contact area.
When the brakes are released, the return springs
overcome the diminishing fluid pressure and return the
brakeshoes and wheel cylinder pistons to the neutral
position.
During a reverse stop, the drum brakes operate in the
same mode as for a forward stop. However, because the
drum is rotating in the opposite direction, the secondary
brakeshoe now operates, in effect, as the primary
brakeshoe.
Parking Brake Operation
The parking brake lever is mounted on the back of the
brakeshoe and and is connected to it by a pivot pin
installed in the upper end of the lever. The pin is re-
tained in the brakeshoe by a washer and U-clip. The
parking brake cable is attached to the lower end of the
lever. A strut, located just below the pivot pin, connects
the lever to the primary brakeshoe. The strut is notched
at each end and fits into matching notches in the bra-
keshoe and lever. The strut is positioned in the bra-
keshoe by an oval shaped spring.
When the parking brakes are applied, the cable pulls
the lower end of the lever forward causing the con-
necting strut to push the primary brakeshoe forward
also. At the same time, the upper end of the lever pushes
the secondary brakeshoe rearward. The combined action
of lever and strut expands the brakeshoes forcing them
against the drum to develop braking action.
Wear Coipensation
The automatic adjuster mechanism continuously
maintains correct lining-to-drum operating clearance by
adjusting the brakes in small increments in direct pro-
portion to lining wear. This continuous adjustment pre-
vents a gradual increase in brake pedal travel as the
linings wear. The adjuster mechanism also adds the
safety feature of maintaining adequate pedal reserve
during the service life of the lining.