How do you know the size of car tires?

To determine the size of car tires, you need to look at the tire sidewall. The tire size is typically displayed in a series of numbers and letters, which indicate the tire's width, aspect ratio, wheel diameter, and load index.

Here's how to read a tire size:

1. Width: The first number in the tire size sequence indicates the tire's width in millimeters. For example, a tire with a size of 205/55R16 has a width of 205 millimeters.

2. Aspect Ratio: The second number in the tire size sequence represents the tire's aspect ratio. It is the ratio of the tire's height to its width. For example, a tire with a size of 205/55R16 has an aspect ratio of 55%, meaning that the tire's height is 55% of its width.

3. Construction: The third letter in the tire size sequence indicates the tire's construction. "R" stands for radial construction, which is the most common type of tire construction.

4. Wheel Diameter: The fourth number in the tire size sequence represents the diameter of the wheel that the tire is designed to fit. For example, a tire with a size of 205/55R16 has a wheel diameter of 16 inches.

5. Load Index: The last number in the tire size sequence represents the tire's load index, which indicates the maximum load that the tire can carry at its maximum permissible inflation pressure. For example, a tire with a size of 205/55R16 91V has a load index of 91, which corresponds to a maximum load of 1354 lbs (614 kg).

Additionally, some tire sizes may also include a speed rating, which is indicated by a letter after the load index. For example, a tire with a size of 205/55R16 91V has a speed rating of V, which indicates that the tire is suitable for speeds up to 149 mph (240 km/h).