Maintenance
269
Tires and wheels
tions of their use, however, and
may depart significantly from the
norm due to variations in driving
habits, service practices and dif
-
ferences in road characteristics
and climate.
These grades are molded on the
side-walls of passenger vehicle
tires. The tires available as stan
-
dard or optional equipment on
your vehicle may vary with
respect to grade.
Traction - AA, A, B & C
The traction grades, from highest
to lowest, are AA, A, B and C.
Those grades represent the tire's
ability to stop on wet pavement
as measured under controlled
conditions on specified govern
-
ment test surfaces of asphalt and
concrete. A tire marked C may
have poor traction performance.
The traction grade assigned to
this tire is based on straight-
ahead braking traction tests, and
does not include acceleration,
cornering, hydroplaning, or peak
traction characteristics.
Temperature -A, B & C
The temperature grades are A
(the highest), B and C represent
-
ing the tire's resistance to the
generation of heat and its ability
to dissipate heat when tested
under controlled conditions on a
specified indoor laboratory test
wheel.
Sustained high temperature can
cause the material of the tire to
degenerate and reduce tire life,
and excessive temperature can
lead to sudden tire failure. The
grade C corresponds to a level of
performance which all passenger
vehicle tires must meet under the
Federal Motor Vehicle Safety
Standard No. 109. Grades B and
A represent higher levels of per
-
formance on the laboratory test
wheel than the minimum
required by law.
Tire terminology and defini
-
tions
Refer to the following for detailed
definitions of the terms that are
found in the tire description.
Air Pressure
The amount of air
inside the tire pressing outward
on the tire. Air pressure is
expressed in pounds per square
inch (psi) or kilopascal (kPa).
Accessory Weight
This means
the combined weight of optional
accessories. Some examples of
optional accessories are auto
-
matic transaxle, power seats, and
air conditioning.
Aspect Ratio
The relationship of
a tire's height to its width.
Belt
A rubber coated layer of
cords that is located between the
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