How to Read & Determine Tire Size of Your Vehicle
An assortment of characters on a tire’s sidewall can be difficult to read; here are a few tips to determine your tire size.
While road safety depends on your vehicle’s ability to handle the road, pinpointing the right tire size is important. When looking at a tire’s sidewall, you’ll notice two things that stand out: the manufacturer’s name and the size. The size format can be presented in a few different ways but it should be easy to locate. Let’s look at the example tire code LT275/65R18/S to find out what each of the characters represents.
This letter group is the suggested use of the tire. The letters “LT”, from our example, indicates the tire is for a light truck. In other cases, “P” would represent that the tire is for a passenger car. This applies only to American tires as European metric tires have no letter at the start of the code.
The width of a tire is measured in millimeters and represents the length between the sidewalls. In our example above, the tire is 275 millimeters wide. A wider tire covers more surface of the road and a better grip on the road.
This is the height to width ratio of a tire’s cross-section. For our example, the number ‘65’ represents a tire with a height equal to 65% of its width. This important sizing calculation indicates the general performance or lateral stability of a tire.
This letter represents the way a tire was constructed. The “R” in our example means radial, meaning the tire was constructed via layers radially running across the tire. A “B” represents a bias construction method where the layers of the tire run diagonally.
A wheel’s rim diameter is the total length of a wheel from one side to the other, in our case “18”. When replacing a tire, always ensure the new tire is the same rim diameter as the original tire. You’ll likely need roadside assistance if you get this one wrong! 😀
This metric indicates the tire’s load-carrying capacity or the maximum weight the tire is designed to carry. The load index for a typical passenger car varies from 75 to 100; look for the figure in pounds or kilograms somewhere on the tire sidewall.
Tires can only operate safely within certain speed limits. The speed rating is the maximum speed a tire can function at. In our example, “S” is designed for speeds up to 112 miles per hour. This safety warning keeps drivers within an appropriate range
AuXcar is always here to provide world-class breakdown assistance at a touch. Spare tire changes, battery jumpstarts, engine code checks, towing trucks, and emergency fuel are available from a network of talented automotive service providers. As a driver, it is your responsibility to have the right tire. Check your tires today to stay safe on the road.