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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 at tire or other tire failure.
6.4.1 Safety rst–Basic tire maintenance
Properly maintained tires improve the steering, stopping, traction, and load-
carrying capability of your vehicle. Under-inated 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.
6.4.2 Finding your vehicle’s recommended tire pressure and load limits
Tire information placards and vehicle certication labels contain information on
tires and load limits. These labels indicate the vehicle manufacturer’s information
including:
• Recommended tire size
• Recommended tire ination 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 certication labels are permanently attached to the trailer near
the left front.
6.4.3 Understanding tire pressure and load limits
Tire ination 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
ination pressure is a number that indicates the amount of air pressure– measured
in pounds per square inch (psi)–a tire requires to be properly inated. (You will
also 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 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 ination pressure.” (As you
will read below, it is difcult 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 ination 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.