How to read your tire size
Yes, those numbers in the tire size do mean something! Understanding them can save you a lot of trouble! They assure you proper fitment on your car, making shopping easier. As it may be confusing at first glance, let us give you some tips to become a pro!
Tire width
The first number in the tire size indicates the width of the tire in millimeters. For instance, if the tire size reads "225/55R18," the width of the tire is 225 millimeters.
Aspect ratio
Following the width, you'll find a two-digit number: this one is the aspect ratio, which is the ratio of the tire's height to its width. In our example, the aspect ratio is 55, indicating that the tire's height is 55% of its width.
Construction type
The letter "R" stands for the construction type of the tire. "R" stands for radial, which is the most common type of tire construction today. Radial tires have layers of fabric running radially across the tire.
Rim diameter
The number after the construction type letter represents the diameter of the wheel rim in inches. In our example, the rim diameter is 18 inches.
Load index and speed rating
At the very end of the tire size, you may find two more numbers and letters. The first number is the load index, which indicates the maximum weight capacity of the tire. As the number gets higher, the greater the load it can bear.
The second letter is the speed rating, specifying the maximum speed at which the tire can safely operate. Speed ratings range from A (lowest) to Y (highest). For example, a tire with a load index of 97 and a speed rating of T can support up to 1,606 pounds and is rated for a maximum speed of 118 mph. May be useful to know if you pull an RV…!
You may also see…
Some tires sizes may give you more information like specific performance characteristics or seasonal designations. For instance, you might come across terms like "All-Season," "Winter," "M+S" (mud and snow) or “RFT” (run on flat) on the sidewall.
Although you may now know more about tire sizes, it doesn’t mean you don’t need help anymore! That is why you can chat with us or send us an email at any moment: we will gladly help you choose the right tire for your car.
And don't forget! You will find a sticker in the archway on the driver site stating the recommended tire size for your car.