The tire size is a code that is printed on the sidewall of the tire. It tells you the width, aspect ratio, rim diameter, and speed rating of the tire.

The first three digits of the tire size code represent the width of the tire in millimeters. So, a tire size of 205/55 R16 means that the tire is 205 millimeters wide.

The next two digits represent the aspect ratio of the tire. The aspect ratio is the height of the tire as a percentage of its width. So, a tire with an aspect ratio of 55 means that the height of the tire is 55% of its width.

The letter “R” after the aspect ratio stands for radial construction. This means that the tire has a steel belt that is wrapped around the circumference of the tire. Radial tires are more common than cross-ply tires, which have steel belts that are placed diagonally across the tire.

The last two digits of the tire size code represent the rim diameter in inches. So, a tire size of 205/55 R16 means that the tire fits a rim that is 16 inches in diameter.

Here is another example:

• 195/65 R15 91H
  • 195 millimeters wide
  • 65% aspect ratio
  • 15 inches rim diameter
  • 91 load index
  • H speed rating

The load index is a number that tells you the maximum load that the tire can carry. The speed rating is a letter that tells you the maximum speed that the tire can safely operate at.