Tesla MODEL X Owner's Manual page 206

Wheels and Tires
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.
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