Page 176 - Driving Commercial Vehicles Manual+

chapter 8 — air brakes

Some chambers have a built-in release bolt while others have a release bolt,
nut and washer carried in a bracket mounted on the chamber housing.

The spring has been caged
using a caging bolt.

This diagram shows how one type of release bolt is inserted into the rear of
driving tip the spring parking brake housing. The release bolt is then given a quarter
turn to lock it in place. Then the release nut is turned until the spring is
Caging spring parking compressed.
brakes should be done only
in an emergency. Instructions for manual release are usually imprinted on the housing of most
spring parking brake chambers.
Once a spring brake chamber
is caged, there’ll be no Before trying to manually release spring parking brakes, block the wheels to
parking brake force at that prevent the vehicle from rolling. To move a vehicle after manually releasing
wheel. the spring parking brakes call a tow truck.

Spring parking brakes in dual air brake systems

This installation takes advantage of the primary and secondary reservoirs
to supply the parking brake dash control with air from the tank that has the
highest pressure.
fast fact

The effectiveness of spring
parking brakes depends on
how well the brakes have
been kept in adjustment.

Spring parking brakes
installed in a dual air brake
system. The brakes are off.

161