The temperature grades are A (the
highest), B and C, representing 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 car tires must meet
under the Federal Motor Vehicle Safety
Standard No. 139. Grades B and A
represent higher levels of performance on
the laboratory test wheel than the
minimum required by law.
Glossary of Tire Terminology
• Tire label: A label showing the OE
(Original Equipment) tire sizes,
recommended inflation pressure and
the maximum weight the vehicle can
carry.
• Tire Identification Number (TIN): A
number on the sidewall of each tire
providing information about the tire
brand and manufacturing plant, tire
size and date of manufacture. Also
referred to as DOT code.
• Inflation pressure: A measure of the
amount of air in a tire.
• Standard load: A class of P-metric or
Metric tires designed to carry a
maximum load at 35 psi [37 psi (2.5
bar) for Metric tires]. Increasing the
inflation pressure beyond this pressure
will not increase the tire’ s load carrying
capability.
• Extra load: A class of P-metric or
Metric tires designed to carry a heavier
maximum load at 41 psi [43 psi (2.9
bar) for Metric tires]. Increasing the
inflation pressure beyond this pressure
will not increase the tire’ s load carrying
capability.
• kPa: Kilopascal, a metric unit of air
pressure.
• PSI: Pounds per square inch, a
standard unit of air pressure.
• Cold inflation pressure: The tire
pressure when the vehicle has been
stationary and out of direct sunlight for
an hour or more and prior to the vehicle
being driven for 1 mile (1.6 km).
• Recommended inflation pressure:
The cold inflation pressure found on
the Safety Compliance Certification
Label (affixed to either the door hinge
pillar, door-latch post, or the door edge
that meets the door-latch post, next
to the driver's seating position), or Tire
Label located on the B-Pillar or the
edge of the driver’s door.
• B-pillar: The structural member at the
side of the vehicle behind the front
door
• Bead area of the tire: Area of the tire
next to the rim.
• Sidewall of the tire: Area between
the bead area and the tread.
• Tread area of the tire: Area of the
perimeter of the tire that contacts the
road when mounted on the vehicle.
• Rim: The metal support (wheel) for a
tire or a tire and tube assembly upon
which the tire beads are seated.
Information Contained on the Tire
Sidewall
Both U.S. and Canada Federal regulations
require tire manufacturers to place
standardized information on the sidewall
of all tires. This information identifies and
describes the fundamental characteristics
of the tire and also provides a U.S. DOT
Tire Identification Number for safety
standard certification and in case of a
recall.
246
Wheels and Tires
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Curb Weight
Weight and Dimensions
