How to Read Tire Size

September 6th, 2018 by

How to Read Tire SizeThe tires on your vehicle provide you with the necessary grip for the roads of West Valley, Murray City, and Orem. When it’s time for you to replace your current tires with a new set, make sure you’re choosing the right ones by reading the size of your tires.

Fortunately, our team at Volkswagen SouthTowne is here to provide you with some insight on how to do exactly that with this handy guide on how to read tire size. Thanks to the step-by-step information in this manual, you’ll tackle your first new tire purchase with confidence!

Determining Your Tire Type

First things first: Once you’ve found the size code on the sidewall of your tire, you’ll want to start with the first symbol on the left and work your way to the last symbol on the right, just how you would read a sentence.

In most cases, the first thing you’ll see on your tire’s size is a “P” which stands for “passenger vehicle.” This letter simply indicates that your tires are designed for a passenger automobile like a sedan or an SUV.

Tire Width

The next symbol you’ll notice on the sidewall of your tire is a three-digit number. This measurement is your tire’s width in millimeters measured from one sidewall to the other. Depending on your performance needs, you’re welcome to choose narrower or wider tires than you currently own.

Tip: Driving in snowy or slippery conditions? Consider purchasing narrower tires so that your vehicle can cut through slush more easily with improved traction.

Understanding Your Aspect Ratio

How to Read Tire SizeAfter your tire’s width measurement and a slash, you’ll notice a two-digit number that represents the aspect ratio of the tire. To determine this numeral, your tire manufacturer compares the tire height to the tire width. This means that if the number you see on the sidewall is 65, the sidewall height is 65% of its width.

Construction & Wheel Diameter

Next up on your tire size test is another letter. Depending on the tread pattern of your tires, it’s possible you’ll see one of three letters ranging from R, B, and D. For the most part, you should see an R located on your tire’s size code. This means that the cord plies on your tires run at 90 degrees, or radially, to the direction of travel. Otherwise, you may own a set of bias-belted tires or bias ply tires.

Immediately following your tire construction symbol is the wheel diameter. This number is important because it tells you the tire diameter that fits on your wheels. Make sure to take note of this so that you purchase a set of tires with the correct diameter measurement.

Load Index and Speed Rating

The second-to-last symbol on this list is the load index, which simply indicates the amount of weight each tire can support when properly inflated. Keep in mind, however, that this is not the actual number of pounds your tires can support. To determine that, you’ll need to look at a load index chart.

Finally, the speed rating on your tires is symbolized by a letter that corresponds to a maximum speed that your tire can withstand. Just like the load index of your tires, this letter acts as a placeholder, so check out a tire speed rating chart to find out how fast your tires can move.

DOT Symbol

Looking for some peace of mind that you’ve chosen sturdy tires? That’s exactly what the DOT symbol indicates. Standing for “Department of Transportation,” this seal tells you that your tires have passed all Federal Motor Vehicle Safety Standards.

Tire Identification Number

Think of your tire’s identification number as its birth certificate, indicating the location of the manufacturer and the week and year it was assembled.

Why is this number so essential? If your tires are recalled for whatever reason, this is the code the manufacturer will use to help identify if your tires are subject to the recall. That way, you can get a set of new tires that comply with the right safety protocols.


While this may seem like a jumble of random letters, the UTQG (Uniform Tire Quality Grading) offers up more information about which tires your car needs. This rating system was developed by the Department of Transportation to help you determine the tires that are right for your traction and capability needs.

For example, a traction grade of AA means that your tires have enough traction to handle slippery road conditions. Meanwhile, a temperature grade of A tells you that the tread of your tires can manage the high heat produced on the road when you’re travelling at speeds over 115 MPH. All in all, these codes give you further insight into the best set of tires for your environment and driving habits.

Find Your Tires Today!

No matter where the roads of West Valley, Murray City, and Orem take you, it pays to know more about what it takes to keep your vehicle performing at its best. By learning how to read tire size, you’ll be sure to select the right tires that’ll match your need for speed and keep your car healthy for years to come.

Ready to purchase a new set of tires? All you have to do is visit the service center at Volkswagen SouthTowne or schedule your appointment today!

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