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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 fl at tire
or other tire failure.
3.5.1 Safety First- Basic Tire Maintenance
Properly maintained tires improve the steering,
stopping, traction, and load-carrying capability of
your vehicle. Underinfl ated tires and overloaded
vehicles are a major cause of tire failure. Therefore,
as mentioned above, to avoid fl 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.
3.5.2 Finding Your Vehicle's Recommended
Tire Pressure And Load Limits
Tire information placards and vehicle certifi cation
labels contain information on tires and load limits.
These labels indicate the vehicle manufacturer's
information including:
Recommended tire size
•
Recommended tire infl 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 certifi cation labels are
•
permanently attached to the trailer near the left
front.
3.5.3 Understanding Tire Pressure And Load
Limits
Tire infl 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 infl ation
pressure is a number that indicates the amount of
air pressure– measured in pounds per square inch
(psi)–a tire requires to be properly infl ated. (You
will also fi nd 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
Tire Safety
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 infl ation pressure."
(As you will read below, it is diffi 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 infl 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.
3.5.4 Safety First- Basic Tire Maintenance
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 under infl 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 infl ation pressure that
vehicle manufacturers provide refl ects 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.
3.5.5 Steps For Maintaining Proper Tire
Pressure
Locate the recommended tire pressure on the
1.
vehicle's tire information placard, certifi cation
label, or in the owner's manual.
Record the tire pressure of all tires.
2.
If the tire pressure is too high in any of the tires,
3.
slowly release air by gently pressing on the tire
valve stem with the edge of your tire gauge until
you get to the correct pressure.
If the tire pressure is too low, note the difference
4.
between the measured tire pressure and the
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