Tire Markings 101
The Markings on the Tire are puzzling. Here are the pieces. 
Sidewall Outer Circle
P as in P215/65 R 16 89H M+S
The “P” indicates the tire is for passenger vehicles.
LT = light truck
HT = Heavy truck
ST = Special Trailer tire
TT = Tractor tire
Nominal Width (215)
This three-digit number gives the width in millimeters of the tire from sidewall edge to sidewall edge. In general, the larger the number, the wider the tire.
Aspect Ratio
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.
The “R” stands for radial. Radial ply construction of tires has been the industry standard for the past 20 years.
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
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.
Severe snow conditions
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.
Speed Rating
“Note” If your tires aren’t speed rated you should never exceed 99MPH
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.
|
Q |
99 mph |
H |
130 mph |
|
R |
106 mph |
V |
149 mph |
|
S |
112 mph |
W |
168 mph* |
|
T |
118 mph |
Y |
186 mph* |
|
U |
124 mph |
|
|
*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.
Of current tires:
- 3% are rated “AA”
- 75% are rated “A”
- 22% are rated “B”
- only 1 line of tires rated “C”
- 27% are rated “A”
- 59% are rated “B”
- 11% are rated “C”
A control tire is assigned a grade of 100. Other tires are compared to the control tire. For example, a tire grade of 200 should wear twice as long as the control tire.
Of current tires:
- 15% are rated below 200
- 25% are rated 201 – 300
- 32% are rated 301 – 400
- 20% are rated 401 – 500
- 6% are rated 501 – 600
- 2% are rated above 600
Passenger Vehicle – Sidewall Inner Circle
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 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.
This number indicates the maximum load in kilograms and pounds that can be carried by the tire.
This number is the greatest amount of air pressure that should ever be put in the tire under normal driving conditions. For more info visit Safecar.gov
One Comment on “Tire Markings 101”
I heard info on the radio show while riding back from dropping my son’s car off for new tires. I called in to inquire about the “codes” on the side of a tire so we will know (upon pick up) of the age of the tires that are going to be put on his car. The radio station took my call promptly, and gave me this web site to get the information I was asking about. It is very helpful, and I appreciate the promptness of the reply to my call-in question. Thanks!!!