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Studies of tire safety show that maintaining proper tire
pressure, observing tire and vehicle load limits (not
carrying more weight in your vehicle than your tires or
vehicle can safely handle), avoiding road hazards, and
inspecting tires for cuts, slashes, and other irregularities are
the most important things you can do to avoid tire failure,
such as tread separation or blowout and at tires. These
actions, along with other care and maintenance activities,
can also:
Improve vehicle handling
Help protect you and others from avoidable
breakdowns and accidents
Improve fuel economy
Increase the life of your tires.
This manual presents an overview of tire safety, including
information on the following topics:
Basic tire maintenance
Uniform Tire Quality Grading System
Fundamental characteristics of tires
Tire safety tips.
Use this information to make tire safety a regular part of
your vehicle maintenance routine. Recognize that the time
you spend is minimal compared with the inconvenience and
safety consequences of a at tire or other tire failure.
Safety First–Basic Tire Maintenance
Properly maintained tires improve the steering, stopping,
traction, and load-carrying capability of your vehicle.
Underin ated tires and overloaded vehicles are a major
cause of tire failure.
Therefore, as mentioned above, to avoid at 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.
Finding Your Vehicle’s Recommended Tire Pressure
and Load Limits
Tire information placards and vehicle certi cation labels
contain information on tires and load limits. These
labels indicate the vehicle manufacturer’s information
including:
Recommended tire size
Recommended tire in ation 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 certi cation labels are permanently
attached to the trailer on the forward half of the left side,
and are easily readable from outside the vehicle without
moving any part of the vehicle.
Understanding Tire Pressure and Load Limits
Tire in ation 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 in ated. (You will also nd
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 in ation pressure.” (As you
will read below, it is dif cult 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 in ation 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.
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 underin ation 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.
