Section 10 --- Chassis Information
The Executive 2005
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BRAKE SYSTEMS - Air Brakes
The air brake system on the motorhome differs from a conventional automotive hydraulic braking
system and should be treated differently. Proper maintenance and lubrication are the keys to keeping
the air brake system in proper working order.
Consideration needs to be given to stopping distances and air system pressures. The motorhome
requires longer stopping distances. Each brake application uses air from the air system, and engine
speed is directly proportional to how fast that air system is replenished. Prepare for downhill grades. It
may be necessary to select a lower gear and/or use the engine brake. Use individual short brake
applications down long hills, rather than “riding” the brakes, to extend the life of the brake lining.
Avoid overheating the brakes. Hot brakes have less stopping power. When maneuvering the
motorhome around small areas, or backing into spaces, several individual brake applications might be
made. Watch the air gauge. When preparing to back into a space swing the motorhome so it is aligned
with the parking slot before backing up.
The air braking system on the motorhome is equipped with low air pressure warning system safety
feature. Should a low air condition arise while the vehicle is in operation, a warning buzzer will sound
and a dash warning light will illuminate at approximately 60 to 65 psi (pounds per square inch) to alert
the operator.
A simple mechanical explanation of what occurs when a brake application is made is as follows:
The air system supplies air to the foot brake, or treadle valve. Pushing down on the treadle valve sup-
plies an air charge signal to a sealed brake chamber that consists of a spring and air bladder. The air
charge signal pushes on the bladder and extends a threaded rod connected to the automatic slack
adjuster. The slack adjuster rotates the S-cam expanding the shoes against the drum. Air disc brakes
follow much the same principle, with the exception of the threaded rod directly activating calipers.
Park & Emergency Brake System
The Park and Emergency Brake System (Spring Brakes) applies to the rear drive axle only. When
the park brake is applied, air is released from the rear brake chambers, allowing the large spring in each
rear brake chamber to manually push the brake pads against the rotor. The air system must be charged
above 35 psi to allow the park brake to release. Pushing down on the park brake handle charges the rear
brake chambers with air pressure, overriding the emergency brake springs and releasing the brakes. In
the event of air loss, while the vehicle is under operation, the park brake will automatically apply
(this occurs at approximately 30 psi) acting as an automatic emergency brake system.
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