How Do I Read Tire Size?

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At Fred Beans, we can’t stress enough about how important your tires are to your car. This is especially true around the Doylestown, Philadelphia, Flemington, and Mechanicsburg areas, where the rough roads can wear your tires down quicker than you might think.

As soon as your tires start to incur damage, you’ll want to get them changed. At which time, you’ll probably want to check out this detailed article explaining how to read tire sizes. Afterwards, you’ll know exactly what you need.

Reading the Numbers on Your Tire Sidewall

The necessary size of your tires will always be listed on the tire’s sidewall. This appears as a sequence of different numbers and letters, some of which may seem nonsensical. However, if you read the following guide, which explains the sequence from left to right, it’s actually quite simple to decipher.

Tire Class

How Do I Read Tire Size?Are you driving a passenger car or a light truck? If you can’t tell just from looking, then your tire will tell you first thing, either by listing a “P” or an “LT,” respectively.

Section Width

Before selecting new tires, you need to know exactly how wide they should be. That’s what this number will tell you. Section width is always measured in millimeters, so it may appear in the hundreds.

Aspect Ratio

There should always be a slash after the section width, separating it from this important number, the aspect ratio. This indicates the height of your sidewall, as a percentage of the section width.

Primary Speed Rating

Different cars are going to be capable of different speeds. These capabilities will then be reflected in your tire as a speed rating. These ratings are denoted as “S,” “T,” and “Z” (from lowest to highest speed).

Radial Construction

If you see an “R” next, which you probably will, then that means your tires are radial tires. Despite having such a technical name, it just means that you have the most popular type of tire on the road—one fortified with thick layers of corded fabric.

Wheel Diameter

How Do I Read Tire Size?Capping off the first string of numbers and letters is the wheel diameter. Only a certain tire diameter is going to fit your wheel, and this tells you exactly what it is and is shown in inches.

Load Index

Tires take a lot of abuse. By that, we mean they carry a whole lot of weight. This number will tell you just how much they can take. It’s okay to choose a tire with a load index higher than the manufacturer recommendation, but you should never go any lower than that.

Secondary Speed Rating

If your primary speed rating was a “Z” (i.e. super high), you’re going to need a bit of extra specification as to just how fast those tires can go. This second rating, listed either as a “W” or “Y,” will tell you just that.

Schedule a Tire Appointment Today

Now that you know what tire size you need, it might be time to go ahead and replace them. In which case, we encourage all Doylestown, Philadelphia, Flemington, and Mechanicsburg drivers to contact the Fred Beans team as soon as possible!

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