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How to Read Tire Sizes

July 18, 2020

If you guys have ever looked at a tire size chart and thought it was a little overwhelming, well, that's because it is. There is a ton of information to break down when trying to decide on what's the best tire size to purchase for your own application, and it can be a real challenge, and also why we have a gallery on our website, made specifically to see what size tire fits, and what doesn't, and that helps take a lot of that guesswork out of trying to figure it out for yourselves. But first, we have to understand how to read the tire sizes.

 

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To start, there are two different types of listed measurements for tire sizes. One of them is metric, and the other is flotation.

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1. Metric Sizes

Metric sizes start with a number in millimeters and there are four different designation categories for metric sizes. There's P for passenger, LT for light truck, then ST for special trailer, then T for temporary tire. Typically the designation is imprinted before the number, and if it's not, then most likely it's a passenger tire. The first number on a metric size is what's known as the section width of the tire, or basically the width of the tire, and is measured from the sidewall to the other sidewall in millimeters.

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The next number is a percentage of the first number and is used to determine the height of the sidewall. After that, the next number is the size of the wheel. Typically you will see an R that separates the sidewall height number and the size of the wheel number, and that'll tell you that is a radial ply constructed tire, as opposed to its counterpart the bias ply.

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Radial tires are the most common tires on the market for passenger vehicles, as their construction allows for a much better ride compared to the bias ply. Light truck tires will have additional what are called plies, or layers, of woven nylon or steel to construct what is known as the carcass of the tire. They'll also have a thicker rubber, deeper tread, and stronger bead bundle. The more plies or layers there are, the stronger the tire is, plus, are capable of holding a higher pressure of air.

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2. Flotation Sizes

All right guys, now that we have that covered in metric sizes, flotation sizes are much easier to understand as their number directly relates to the tire's measurement in inches. The first number is the height of the tire in inches, the second number is the width of the tire in inches, and the third number the wheel size.

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For example, we have a 35 inch by 12.50, 17, which means the tire is 35 inches tall, 12 and a half inches wide, and fits a 17 inch wheel. We also have a calculator on our website to help you convert the metric sizes into floatation sizes and vice versa. The calculator will give you a good idea on how your new offroad tires fit your rig.

That about wraps it up! Hopefully, this guide helped you learn a little more about the tires you may be adding to your rig!