Uniform Tire Quality Grading - Tesla Model S Owner Safety Information

UNIFORM TIRE QUALITY GRADING

The following information relates to the tire grading system developed by
the National Highway Traffic Safety Administration (NHTSA) which grades
tires by tread wear, traction and temperature performance. Tires that have
deep tread, and winter tires, are exempt from these marking requirements.
Quality grades
Where applicable, quality grades can be found on the tire sidewall
between the tread shoulder and maximum section width. For example:
TREADWEAR 180 TRACTION AA
In addition to the marking requirements, passenger car tires must conform
to Federal Safety Requirements.
Treadwear
The treadwear grade is a comparative rating based on the wear rate of the
tire when tested under controlled conditions on a specified government
test course.
For example, a tire graded 150 would wear one and a half times better on
a government test course than a tire graded 100. The relative performance
of tires depends on the actual conditions of their use, however, and may
depart significantly from the norm due to variations in driving habits,
service practices, and differences in road characteristics and climate.
Traction
The traction grades, from highest to lowest, are: AA, A, B, and C. These
grades represent a tire's ability to stop on wet pavement as measured
under controlled conditions on test surfaces of asphalt and concrete. A tire
marked C may have poor traction performance.
Temperature
The temperature grades are A (the highest), B, and C, representing the
TEMPERATURE A
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 tire to degenerate
and reduce tire life, and excessive temperature can lead to sudden tire
failure.
The grade C corresponds to the minimum level of performance that all
passenger car tires must meet under the Federal Motor Safety Standard
No. 109. Grades B and A represent levels of performance on the laboratory
test wheel that exceed the minimum requirements.
Tire performance decreases at low ambient temperatures, resulting in
reduced grip and increased susceptibility to damage from impacts. In
temperatures below 15° F (-10° C), winter tires are recommended. Contact
Tesla for recommended winter tire specifications.
WARNINGS:
Defective tires are dangerous. Do not drive if a tire is damaged, excessively
worn, or is inflated to an incorrect pressure. The safety of the vehicle and
occupants can be adversely affected. Check tires regularly for wear and to
ensure there are no cuts, bulges or exposure of the ply/cord structure.
The traction grade assigned to the tire is based on straight-ahead braking
tests, and doesn't include: acceleration, cornering, hydroplaning or peak
traction characteristics.
WARNING: A tire's temperature grade is established for a tire that is
properly inflated and not overloaded. Excessive speed, under-inflation, or
excessive loading, either separately or in combination, can cause heat
buildup and possible tire failure.
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