Size Does Matter: A Short Explanation of Tire Sizes
The size of the tire is located on the sidewall. It should be in raised letters and numbers and is easy to see. If your eyesight is anything like the writer’s, you might need a magnifying glass to see it. All measurements are in inches, except for one kind of tire which we will get to in a minute. Here are some examples:
- The size 18x8.50-8 reads like this: 18" is the height, 8.50" is the width, and 8" is the diameter of the wheel.
- The numbers 4.80/4.00-8 read like this: 4.80" is the tire width, 4.00" is the tire section height (from the inside of the donut hole to the outside) and the 8" is the wheel diameter.
- Finally, the numbers 4.80-8 read like this: 4.80" is the tire width and "8 is the wheel diameter.
In a different way of measuring tires, centimeters are used instead of inches. If you see large two or three digit numbers it's probably metric. For example, the size 215/60-8 is mostly metric, except the last part is the diameter of 8 inches.
A ply rating or actual ply will be listed on the sidewall of the tire like the size is listed. For details on how ply ratings are listed and what they mean click here to read about ply ratings.
Check the Maximum PSI, too!
A maximum PSI will also be listed on the sidewall. Make sure you do not exceed the maximum PSI recommended for each tire. Getting knocked on your butt by an exploding tire is no fun. Also make sure when inflating that you use the maximum PSI as your guide. Underinflated tires will not wear properly and you will not get your money’s worth if they don’t have enough air in them.
Usually you would not need to know what all the numbers mean, but it is great to have a basic understanding. When purchasing a new tire, you will only need to know the numbers on the sidewall of the tire to purchase the correct size.