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Chapter 4 - Safety Provisions
UNDERSTANDING TIRE
PRESSURE & LOAD
LIMITS
TIRE PRESSURE
TIRE SIZE
TIRE TREAD
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•
Vehicle capacity weight (VCW - the maximum occupant and cargo weight a vehicle
is designed to carry)
•
Front and rear gross axle weight rating (GAWR - the maximum weight the axle system
are designed to carry)
Both placards and certification labels are permanently affixed to the motorhomes interior
sidewall. Locate the placards and labels inside of a cabinet door, near to the driver's
area.
Tire inflation pressure is the level of air in the tires that provides it with load-carrying
capacity and affects the overall performance of the vehicle. The tire inflation pressure
is a number that indicates the amount of air pressure - measured in pounds per square
inch (psi) - a tire requires to be properly inflated. (You will also find this number on the
vehicle information placard expressed in kilopascals (kPa), which is the metric measure
used internationally.)
Vehicle manufacturers determine this number based on the vehicle's design load limit,
that is, the greatest amount of weight a vehicle can safely carry and the vehicle's tire size.
The proper tire pressure for your vehicle is referred to as the "recommended cold inflation
pressure. " (As you read below, it is difficult to obtain the recommended tire pressure if
your tires are not cold.)
Because tires are designed to be used on more than one type of vehicle, tire manufacturers
list the "maximum permissible inflation pressure" on the tire sidewall. This number is the
greatest amount of air pressure that should ever be put in the tire under normal driving
conditions.
It is important to check your vehicle's tire pressure before each trip for the following
reasons:
•
Most tires may naturally lose air over time
•
Tires can lose air suddenly if you drive over a pothole or other object or if you
strike the curb when parking
•
With radial tires, it is usually not possible to determine under inflation by visual
inspection
For convenience, purchase a tire pressure gauge to keep in your
vehicle. Gauges can be purchased at tire dealerships, auto supply stores,
and other retail outlets.
The recommended tire inflation pressure that vehicle manufacturers provide reflects the
proper psi when a tire is cold. The term cold does not relate to the outside temperatures.
Rather, a cold tires is one that has not been driven on for at least three hours. When you
drive, your tires get warmer, causing the air pressure within them to increase. Therefore,
to get an accurate tire pressure reading, you must measure tire pressure when the tires
are cold or compensate for the extra pressure in warm tires.
To maintain tire safety, purchase new tires that are the same size as the vehicle's original
tires or another size recommended by the manufacturer. Look at the tire information
placard, the chassis owner's manual, or in a cabinet for replacing tires. If you have any doubt
about the correct size to choose, consult with your dealer and chassis manufacturer.
The tire tread provides the dripping action and traction that prevent your vehicle from
slipping or sliding, especially when the road is wet or icy. In general, tires are not safe and
should be replaced when the tread is worn down to 1/16" of an inch.
Tires have built-in tread wear indicators that let you know when it is time to replace your
tires. These indicators are raised sections spaced intermittently in the bottom of the tread
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Troubleshooting
