Sidewall: The portion of a tire between the tread and
the bead.
Speed Rating: An alphanumeric code assigned to a
tire indicating the maximum speed at which a tire
can operate.
Traction: The friction between the tire and the road
surface. The amount of grip provided.
Tread: The portion of a tire that comes into contact
with the road.
Treadwear Indicators: Narrow bands, sometimes
called wear bars, that show across the tread of a tire
when only 1/16 inch (1.6 mm) of tread remains.
See When It Is Time for New Tires on page 5-68.
UTQGS (Uniform Tire Quality Grading Standards):
A tire information system that provides consumers
with ratings for a tire’s traction, temperature, and
treadwear. Ratings are determined by tire manufacturers
using government testing procedures. The ratings are
molded into the sidewall of the tire. See Uniform
Tire Quality Grading on page 5-70.
Vehicle Capacity Weight: The number of designated
seating positions multiplied by 150 lbs (68 kg) plus
the rated cargo load. See Loading Your Vehicle
on page 4-31.
Vehicle Maximum Load on the Tire: Load on an
individual tire due to curb weight, accessory weight,
occupant weight, and cargo weight.
Vehicle Placard: A label permanently attached to a
vehicle showing the vehicle’s capacity weight and
the original equipment tire size and recommended
inflation pressure. See “Tire and Loading Information
Label” under Loading Your Vehicle on page 4-31.
Inflation - Tire Pressure
Tires need the correct amount of air pressure to operate
effectively.
Notice: Do not let anyone tell you that
under-inflation or over-inflation is all right. It is not.
If your tires do not have enough air (under-inflation),
you can get the following:
• Too much flexing
• Too much heat
• Tire overloading
• Premature or irregular wear
• Poor handling
• Reduced fuel economy
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