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Recognize that the time you spend is minimal compared with the inconvenience and safety
consequences of a flat tire or other tire failure.
1.6. Safety First
–Basic Tire Maintenance
Properly maintained tires improve the steering, stopping, traction, and load-carrying capability of
your vehicle. Underinflated tires and overloaded vehicles are a major cause of tire failure.
Therefore, as mentioned above, to avoid flat tires and other types of tire failure, you should
maintain proper tire pressure, observe tire and vehicle load limits, avoid road hazards, and
regularly inspect your tires.
1.6.1. Finding Your Vehicle's Recommended Tire Pressure and Load Limits
Tire information placards and vehicle certification labels contain information on tires and load
limits. These labels indicate the vehicle manufacturer's information including:
Recommended tire size
Recommended tire inflation pressure
Vehicle capacity weight (VCW
–the maximum occupant and cargo weight a vehicle is
designed to carry)
Front and rear gross axle weight ratings (GAWR
– the maximum weight the axle systems
are designed to carry).
Both placards and certification labels are permanently attached to the trailer near the left
front.
1.6.2. Understanding Tire Pressure and Load Limits
Tire inflation pressure is the level of air in the tire 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.)
Manufacturers of passenger vehicles and light trucks 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 will 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.
1.6.3. Checking Tire Pressure
It is important to check your vehicle's tire pressure at least once a month 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 underinflation 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 temperature. Rather, a cold
tire 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.
