Tire Side Wall Markings
Locate the series of numbers on the tire sidewall, then
Use the diagram above and the list below to find the meaning of each number.
Tire Type – 1
Tire type defines the proper use of the tire. For example, the letter “P” indicates a passenger car tire. The letters “LT” would indicate a light truck, “ST” is the abbreviation for special trailer and “T” is a temporary tire such as a space-saver spare. Also, when a letter before the width is not present it indicates a metric-sized tire.
Tire Width – 2
The width of the tire measured in mm from sidewall to sidewall. In this case, the tire width is 215 mm.
Tire Height – 3
The height of a tire’s sidewall is referred to as the aspect ratio. The aspect ratio is calculated as a percentage of the tire width. In the image above, the number 60 means that the tire sidewall height is equal to 60% of the tire’s width. The higher the aspect ratio number the higher the height of tire sidewall.
Tire Construction – 4
Tire construction indicates how the layers of the tire are put together. Hence, the letter “R” stands for radial, which means the layers run radially across the tire. The letter “B” stands for bias construction, and the letter “D” stands for diagonal construction. Consequently, both mean the layers run diagonally across the tire.
Different construction serve different purposes. Therefore, mixing different constructed tires on a vehicle can cause poor handling and tire failure.
Rim diameter – 5
The rim diameter is the width of the tire in inches or cm from one end to the other. The diameter of the wheel in the image above is 16 inches. Most noteworthy, always replace a tire on a rim with another tire of the same rim diameter designation and suffix letters
Load index – 6
An assigned number that corresponds with the load-carrying capacity of a tire. Most passenger car tire load indexes range from 75 to 100, but a few carry more. Also, you can find the maximum load elsewhere on the tire sidewall, both in lbs. and kg. Learn more about tire load index at RVTires.com How is a Tires Load Capacity Determined?
Speed Rating – 7
The speed rating is the maximum service speed for a tire. A speed rating is not a recommendation to exceed speed limits. Furthermore, it doesn’t indicate how well a tire handles or corners. To Learn more, read about tire Speed Rating.