PART 7: STARTING & OPERATING THE VEHICLE
PB1319 (CAT. NO. 5296 ) —79— 22-01691 (R02/02)
the drive wheel brakes. Engine torque or vehicle speed should be
reduced to eliminate wheel spin and prevent excessive application of
the ATC system.
Except for checking for proper illumination of the ABS and Wheel
Spin Control warning lamps when first starting the truck and for moni-
toring these lamps while driving, no special operating procedures are
required. For detailed system description, see service literature for
your specific ABS that was provided with your vehicle.
Bobtail Brake Proportioning System
Peterbilt tractors that do not have anti-lock brake systems (ABS) are
typically equipped with a bobtail brake proportioning system. When a
trailer is not connected, the drive axle brake application pressure will
automatically be limited by the proportioning system.
When driven in a bobtail mode, these tractors will require greater
brake pedal application to provide the equivalent braking to a bobtail
tractor not equipped with a proportioning system.
Emergency Braking
To stop your vehicle in an emergency, vary the service brake applica-
tion pressure to provide maximum braking force without locking the
wheels. Use engine compression to assist the service brakes; i.e.,
don’t depress the clutch pedal until the engine reaches idle speed.
NOTE: The following information is applicable only to tractor
configurations built on or after March 1, 1997 and not regis-
tered in the United States.
WARNING! Because of the increased use of the steer
axle brakes when driving bobtail, always ensure the
steer axle brakes are functioning and properly adjusted.
Failure to do so can lead to decreased braking ability,
longer stopping distances, loss of vehicle control, and
can cause an accident.
WARNING! Unless you have an anti-lock braking sys-
tem, always avoid completely depressing the service
brake pedal, if possible, even during emergency brak-
ing. Depressing the brake pedal too aggressively can
cause the wheels to lock, which can lead to an uncon-
trolled skid and could cause an accident.
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