How to measure tire size

The size of the tire is usually written and determined in terms of millimeter, inches, or a combination of these two units. In the most commonly used size recording methods of radial tires, tire section width, the aspect ratio and the diameter of the rim are considered. In some of size recording systems, the load index and speed symbol are inserted with the sizes. Also, in order to determine the grouping of a tire in terms of belonging to passenger car, pickup truck or truck, before the size of the tire the letters P (Passenger) is meant to be a passenger car, and at the end of the size of the light truck tires, letters "LT" stands for the "Light Truck", meaning a pickup truck is inserted. The most common types of recording techniques are as follows:

-Bias Tire Recording Size 20-10.00

In the above example, 10.00 is the tire nominal width section in inches, the "-" sign represents the structure of the bias and the number 20 is the rim's nominal diameter in inches.

This type of size recording is used for bias tires of passenger car, vans, and truck.

In the bias tires, the aspect ratio is in the range of 82 to 100.

-Passenger car radial tire size 195/65 R15 91H.

In this method, which is the most common way to measure the size of passenger car radial tires, 195 indicates the tire's nominal width section in millimeters, 65 is aspect ratio, R represents radial structure and the number 15 is the nominal diameter of the rim in inches. Also in the example above, 91 is the load index and H represents the tire speed symbol.