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OPERATION 159
BRAKE OPERATION
Air Brake System
This chassis features a dual braking system which has two complete air
circuits: a primary circuit for rear brakes and a secondary circuit for front
brakes. Each circuit receives air from separate reservoirs. Although there are
two air circuits, they operate as one brake system through the dual-circuit
treadle valve. This provides the driver with easy, graduated control when
applying and releasing the brakes.
The air pressure in the two circuits is monitored by gauges on the instrument
panel. When air pressure drops below 517 ± 34 kPa (75 ± 5 psi) in either
system at any time other than vehicle startup, pull to the side of the road and
determine the problem. If air pressure continues to drop below 40 ± 5 psi in
BOTH systems, spring brakes will automatically apply. The Low Air Pressure
Warning indicator and buzzer will be activated if low air pressure occurs
in either circuit.
In tractor applications, the Trailer Supply Valve (red octagonal knob) will
immediately pop out in the event of a trailer breakaway or sudden trailer air
line failure, which will apply the trailer spring brakes. In the event of a slow
leak in the trailer air system, the trailer supply valve will pop out when system
Pressure reaches 70 psi. This protects the tractor air system from further
pressure loss.
If the Trailer Supply Valve is held in, in an attempt to override application of
the trailer spring brakes, the Park Brake Valve (yellow diamond knob) will
automatically pop out and apply the parking brakes when system pressure
drops to approximately 20–30 psi.
The air brake system consists of three main elements:
• The compressor, governor and reservoirs supply and store the air pressure.
• The brake application valve controls the brake application pressures.
• The brake chambers control the brake mechanism.
Air Brake Operation
CAUTION
Avoid sudden stops. Constant, sudden stops may negatively affect the performance
of braking and driving parts.
Summary of Contents for Granite GU Series
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Page 44: ...SAFETY INFORMATION 33 Advisory Label Locations On Vehicle Labels Found on Chassis C0029831 ...
Page 45: ...34 SAFETY INFORMATION C0028958 ...
Page 46: ...SAFETY INFORMATION 35 C0028959 ...
Page 47: ...36 SAFETY INFORMATION C0029013 1 Right Side Frame Rail 2 Hood Prop ...
Page 48: ...SAFETY INFORMATION 37 C0029014 ...
Page 49: ...38 SAFETY INFORMATION Labels Found on Driver Side Sun Visor C0029832 ...
Page 50: ...SAFETY INFORMATION 39 C0029016 ...
Page 58: ...SAFETY INFORMATION 47 C0029833 ...
Page 60: ...SAFETY INFORMATION 49 C0029834 ...
Page 62: ...SAFETY INFORMATION 51 C0029835 ...
Page 72: ...INSTRUMENTS AND CONTROLS 61 Panel B W3056238 ...
Page 81: ...70 INSTRUMENTS AND CONTROLS C0029141 ...
Page 82: ...INSTRUMENTS AND CONTROLS 71 Diagnostics W3036575 W3036576 W3036583 ...
Page 84: ...INSTRUMENTS AND CONTROLS 73 C0029144 ...
Page 113: ...102 INSTRUMENTS AND CONTROLS C0029240 C0029241 ...
Page 235: ...224 OPERATION C0029351 ...
Page 241: ...230 OPERATION C0029352 ...
Page 284: ...MAINTENANCE AND LUBRICATION 273 C0029851 C0029852 1 Towhook Access ...
Page 305: ...294 MAINTENANCE AND LUBRICATION C0029434 1 Front 2 Back ...
Page 317: ......