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C- This two-digit number, known as the aspect ratio, gives
the tire's ratio of height to width. Numbers of 70 or lower
indicate a short sidewall for improved steering response
and better overall handling on dry pavement.
D- "R" stands for radial. Radial ply construction of tires
has been the industry standard for the past 20 years.
E- This two-digit number is the wheel or rim diameter in
inches. If you change your wheel size, you will have to
purchase new tires to match the new wheel diameter.
F-
(Number) This two- or three-digit number is the tire's load
index. It is a measurement of how much weight each tire
can support. You may find this information in your owner's
manual. If not, contact a local tire dealer. Note: You may
not find this information on all tires because it is not
required by law.
(Letter) The speed rating denotes the speed at which a
tire is designed to be driven for extended periods of time.
The ratings range from 99 miles per hour (mph) to 186
mph. These ratings are listed below. Note: You may not
find this information on all tires because it is not required
by law.
Letter Rating
Q
R
S
T
U
H
V
Y
*Note: For tires with a maximum speed capability over
149 mph, tire manufacturers sometimes use the letters
ZR. For those with a maximum speed capability over 186
mph, tire manufacturers always use the letters ZR.
G- U.S. DOT Tire Identification Number. This begins with
the letters "DOT" and indicates that the tire meets all
federal standards. The next two numbers or letters are
the plant code where it was manufactured, and the last
four numbers represent the week and year the tire was
built. For example, the numbers 3197 means the 31st
week of 1997. The other numbers are marketing codes
used at the manufacturer's discretion. This information
is used to contact consumers if a tire defect requires a
recall.
H- The "M+S" or "M/S" indicates that the tire has some
mud and snow capability. Most radial tires have these
markings; hence, they have some mud and snow
capability.
I- Tire Ply Composition and Materials Used. The number
of plies indicates the number of layers of rubber-coated
fabric in the tire. In general, the greater the number
of plies, the more weight a tire can support. Tire
manufacturers also must indicate the materials in the tire,
which include steel, nylon, polyester, and others.
Speed Rating
99 mph
106 mph
112 mph
118 mph
124 mph
130 mph
168 mph*
186 mph*
J- Maximum Load Rating. This number indicates the
maximum load in kilograms and pounds that can be
carried by the tire.
K- Maximum Permissible Inflation Pressure. This number
is the greatest amount of air pressure that should ever be
put in the tire under normal driving conditions.
Uniform Tire Quality Grading (UTQGS)
Quality grades can be found where applicable on the tire
sidewall between tread shoulder and maximum section
width. For example:
TREADWEAR 200 TRACTION AA
Temperature A
All Passenger Car Tires Must Conform to Federal Safety
Requirements in Addition to These Grades
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 one-half
(11⁄2) times as well on the government course as a tire
graded 100. The relative performance of tires depends
upon 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. Those grades represent the tire's ability to stop on
wet pavement as measured under controlled conditions
on specified government test surfaces of asphalt and
concrete. A tire marked C may have poor traction
performance.
Warning: 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
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
Safety Standard No. 109. Grades B and A represent
higher levels of performance on the laboratory test
wheel than the minimum required by law. Warning: The
temperature grade for this tire is established for a tire that
is properly inflated and not overloaded. Excessive speed,
underinflation, or excessive loading, either separately or
in combination, can cause heat buildup and possible tire
failure.
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