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How to Read Your Tire Size

How to Read Your Tire Size

Knowing how to read your tire size is an important skill to have. After reading the guide below, we think you’ll feel more confident than ever when it comes time to shop for new tires.


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Knowing how to read your tire size is an important skill to have. If you get a flat tire and need a replacement, decide to invest in winter tires, or are looking to buy a whole new set of tires after yours have worn down, knowing the size of tire you require is critical. While the whole concept of tire sizing can seem a little foreign at first, this guide should help you realize that you don’t need a Ph.D. in automotive studies to decode that long sequence of letters and numbers found on the sidewall of your tire. In fact, after reading the guide below, we think you’ll feel more confident than ever when it comes time to shop for new tires.

Where Can You Find Your Tire Size?

The first step in reading your tire size is finding your tire size. Your tire size will look like a long sequence of numbers, often interspersed with a few letters and backslashes. To find it, there are three places to look. The first is on the sidewall of the tire, the second is on the inside of the driver-side door frame, and the third is in the owner’s manual for your vehicle. Searching any of these places should find you what you’re looking for. Once you’ve located the mysterious sequence of numbers, it’s time to decode them (more on that below).

Tire Size Meaning

When you first set eyes on the numbers and letters embedded on the sidewall of your tire, you might be nothing short of confused. That’s normal. Take a deep breath and consider the fact that each grouping of numbers and letters in the sequence has a different meaning, meanings that can be explained as follows. Typically, the tire size will begin with a letter. This letter reveals the type of tire that it is. For example, if your tire size starts with a “P,” the most common type of tire, this means your vehicle is a P-Metric tire, the type of tire intended for passenger vehicles. Alternatively, you might see the letters “LT” at the beginning of the tire size, which tells you that it is a light truck tire, or “ST” which translates to a special trailer tire. If your tire size starts with numbers rather than letters, then it likely means your tire is Euro-Metric, rather than P-Metric, however, both are primarily used for passenger tires.

After the letter(s) found at the beginning of the tire size, if applicable, are a set of numbers that denote the width of the tire. The width is measured in millimetres from sidewall to sidewall and is usually a three-digit number. Next is usually a backslash and after that is another two-digit number, which is the aspect ratio (the height of the tire’s cross-section relative to its width). Then you will likely see another letter, which reveals the construction of the tire. Two types of construction may be found here. The first is Radial, evidenced by the letter “R,” and the second is Diagonal or Bias Ply, marked by either a “D” or “B.” The number that appears after the construction letter is the rim or wheel diameter. The last two metrics are the load index and the speed rating. The load index is the last set of two or three digits in the sequence and it tells you the maximum load or weight in pounds that the tire can support when inflated. Finally, your tire size will likely end with another letter, which is the speed rating, or the maximum speed capability of the tire. Most commonly, this last letter will either be an “S” or an “R,” with the former meaning it’s rated up to 112 mph and the latter meaning it’s rated up to 106 mph.

The Importance of Buying the Right Size Tires

Unfortunately, tire size matters. It’s extremely important to the proper and safe functioning of a vehicle. Purchasing tires that are not the right size for your vehicle could lead to pulling in the steering wheel, a stiffer and noisier ride, rub against the suspension or auto body, and could even reduce clearance on hills. Additionally, it’s worth noting that all four tires on your vehicle should be the same make, model, and size. Mismatched tires on the same vehicle are a recipe for uneven wear, which can lead to major problems long-term. Overall, do everything in your power to ensure the tires you’re buying fit your vehicle perfectly. If you still aren’t sure after trying to decode the numbers on the sidewall of your tire, find a tire size calculator tool online or call Tire Warehouse and speak to one of our experts who would be happy to help you decipher your tire size.

Shop for Tires Online at Tire Warehouse

Now that you know how to read your tire size, shopping for tires online couldn’t be easier (or more risk-free). Knowing the exact size of tire that your vehicle requires is the best way of ensuring that the tires you purchase online will fit your car. To make your online tire shopping experience even more seamless, Tire Warehouse lets you filter your tire search by tire size or vehicle type. So if you know the width, aspect ratio, and rim diameter of your current tires, you can simply enter that information into our website and pages of tailored results showing you only the tires in that specific size will appear. Alternatively, if you find searching by tire size too tedious, you can also search by vehicle, inputting the year, make, and model of the car you require tires for. Ultimately, Tire Warehouse is the go-to online tire provider for a reason. We have been serving Canadians for over 40 years, and during this time, have fine-tuned our online website to make it as intuitive as possible. Plus, we offer shipping for a fee of just $5 per tire, delivery times of just 2 to 4 days, and a mobile installation service, where a professional will install and balance your new tires right there on the spot. If convenience, savings, and quality are what you’re after, look no further than Tire Warehouse.

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