How To Read The Tire Sidewall
Tire Size Example: P235/55R17 98V
P classifies the tire as a Passenger tire, or ‘PMetric. ’ The other most popular designation is LT. These are commonly used on ‘Light Trucks’ and SUVs. Be very wary of any tire starting with ST. This stands for ‘Special Trailer’ and is designed to be used exclusively as a trailer tire. Never use these on a passenger vehicle.
235 identifies the tire section width, which is the measurement of the tire from sidewall to sidewall. This is measured in millimeters and can vary depending on the rim it will be mounted on.
55 denotes the aspect ratio of the tire. This is measured as a percentage which compares the section height with the section width. In this example, the aspect ratio of 55 means that the tire’s section height is 55% of the section width.
R indicates the tire’s casing has a radial construction. This is the most commonly-used type of construction in today’s tires. Other types that are used include B (belted bias) and D (diagonal bias).
17 identifies the rim diameter, measured in inches.
Load Index and Speed Rating
98VThis alphanumeric code describes the load index and speed rating of the tire. The load index indicates the maximum capacity the tire can support when properly inflated. This numeric value corresponds to a specific range on the load index chart, shown below:
|Load Index||Pounds||Kilograms||Load Index||Pounds||Kilograms|
Speed ratings are classified by letters ranging from A to Z. Each letter indicates a specific maximum speed the tire can maintain under its recommended load capacity as determined by the following chart:
|Speed Symbol||Speed (mph)||Speed (km/h)||Use|
|L||75||120||Off-road and light truck tires|
|N||87||140||Temporary spare tires|
|R||106||170||Heavy-duty light truck tires|
|S||112||180||Family sedans & vans|
|T||118||190||Family sedans & vans|
|H||130||210||Sports sedans & coupes|
|V||149||240||Sports sedans, coupes, & sports cars|
|Traction Grade||Asphalt g force||Concrete g force|
|C||Less than .38||.26|
|Temperature Grade||Speed in mph|
|B||Between 100 and 115|
|C||Between 85 and 100|
DOT Serial Number
The “DOT” emblem certifies that the tire was manufactured according to the U.S. Department of Transportation’s safety standards. Prior to the year 2000, three numbers were used to identify the date of manufacture: the first two noting the week (1-52) and the last number telling the year. Since 2000, four numbers are used with the year identified by 2 numbers.