Understanding Tire Size
Learn how to read tire size and choose the right set for your vehicle.
TIRE SIZE EXPLAINED
Tires come in a variety of inner diameters, typically ranging from 13" to 22". The tire size you need will depend on the make and model of your vehicle. Tire size must match rim size and may impact ideal inflation pressure, so knowing the size of your tires is an important part of taking good care of your vehicle.
HOW TO READ TIRE SIZE
If you’re in the market for new tires, the first step is to check the size of your current tires. Simply check the tire placard on the front driver’s side door sill or in the glove box, the Owner’s Manual, or the sidewalls of your tires for a series of numbers and symbols that should look like this: P215/60 R17.
The wheel diameter will be the last number in the series. In this example, the vehicle's rim diameter is 17". The rim size (aka rim diameter) is the most important number to pay attention to when you’re shopping for tires that will fit your vehicle properly.
If you need help choosing tires, check out our Tire Decision Guide.
WHAT DO TIRE SIZES MEAN?
Using the example P215/60 R17, here’s what each number/symbol means:
- P: The tire class or type of tire. P stands for passenger. Another common class is LT for light trucks.
- 215: The tire width measured in millimetres from sidewall to sidewall. Always a 3-digit number.
- 60: Aspect ratio, which is the percentage ratio of a tire’s height to its width. In this example, the tire’s height is 60% of its width.
- R: Tire construction type. Specifies how the cord plies that shape and strengthen the tire are arranged. R stands for radial, which is the standard today.
- 17: Wheel diameter. Tells you what rim size you’ll need for this tire.
If you don’t have existing tires to refer to, you can find your vehicle's recommended tire size by checking the vehicle's tire information placard on the inside of the driver's side door or your owner’s manual.
Shop by tire size
Once you know your car's rim diameter, browse tires by size to find the right tire, at the right price. Then, visit one of our expert technicians at your local Firestone Complete Auto Care. You can trust our tire specialists to mount and balance your new tires. Our tire experts can also offer tire advice if you are considering buying new wheels (rims) or curious about changing the outer diameter of your tires. After all, we've put more tires on more cars than any other company!