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.
Where applicable, quality grades are found on the tire’s sidewall between the tread shoulder and maximum section width. For
example:
• TREADWEAR 180
• TRACTION AA
•
TEMPERATURE A
The quality grades are described next.
NOTE: 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 wears 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 can depart significantly from the
norm due to variations in driving habits, service practices, 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 might have poor
traction performance.
WARNING: 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.
WARNING: The traction grade assigned to the tire is based on straight-ahead braking tests, and does not include:
acceleration, cornering, hydroplaning or peak traction characteristics.
Temperature
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 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.
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.
Tire and Loading Glossaries
General Wheel and Tire Terms
Accessory Weight The combined weight (in excess of those items replaced) of items available as factory installed
equipment.
Wheels and Tires
202 MODEL Y Owner's Manual
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