Matching a tire to a wheel is critical for proper driving and overall safety. Tires of the wrong size can cause serious damage to the vehicle, to property and to individuals. The first step in matching a tire to a wheel is being able to read the tire size. After you know how to read a tire size, you will be able to match a tire to a wheels diameter and determine the correct width and height for your vehicle. There are two distinctive and commonly used ways to represent tire sizes. One way is frequently used on passenger vehicles while the other is frequently used on recreational vehicles, such as ATVs.
Locate a tire's size found on the tire's sidewall. This will consist of three numbers, a slash, two more numbers, and "R," and two more numbers, such as "285/45R19."
Read the first number in the tire size--in the case of our example, that's 285. This is the tire width, in millimeters, measured at the widest point.
Read the second number in the tire size--in our example, that's 65. This is the tire's sidewall height, represented as a percentage of the tire width. Our example tire's height would be 185.25 millimeters (285 multiplied by 65 percent of 285).
Read the third number in the tire size--in our example, that's 19. The third number is the diameter of the hole in the center of the tire--or more precisely, it's the diameter of the wheel on which this tire will fit. If your car or truck's wheel is 19 inches, the two numbers after the "R" on a tire that will fit your wheels must be 19. If your car's rims are 15-inch rims, the numbers after the "R" on a tire that will fit your car must be 15.
Locate the tire size, found on the tire's sidewall. This will look similar to 25X10-12, 25X10X12 or 25-10-12. The separators will vary by the manufacturer, but the order of the numbers will remain the same.
Read the first number in the tire size. 25 is the first number in our example 25X10-12. This represents the approximate tire height in inches.
Read the second number in the tire size. The second number in our example, 10, represents the width of the tire in inches.
Read the third number in the tire size. The third number from our example, 12, represents the size of the rim, in inches, the tire should be mounted upon. An ATV tire whose third number is 12 will fit only on a rim whose diameter is 12 inches.
