Wheels and Tires:
Take the mystery out of buying new tires!
Learn to read the fine print
Thanks to recent tire advances, your tires last a lot longer than they used to. However, even with proper maintenance, tires do wear out and need to be replaced. If you've ever made a trip to a tire store, you probably were inundated with endless tire options. How can you find the right tire to fit your driving habits?
Finding the right size
First off, you'll need to know your tire size. If you look on the sidewall of your current tire, you'll see something like 'P215/75 R15.' That's the size.
All manufacturers use a uniform P-Metric Scale to rate tire size:
Deciphering the Code
Unless you're already familiar with the P Metric Scale, it may be difficult to translate our example tire's code. But with just that little information, an auto pro can install the right tire every time. In fact, in just seconds they could tell you the use; tire width, the tire ratio, type and even the diameter. So let's break it down so you'll know what to look for the next time you buy tires.
 
P 215/ 75 R 15
Tire use: The first letter indicates the category or type of use. Nearly all car tires will be identified with a "P" for passenger.
P=Passenger Tire
C=Commercial Tire
T=Temporary Tire
P 215/ 75 R 15
Tire Width The first number is the tire width, measured in millimeters, from sidewall to sidewall. To convert to inches, divide by 25.4. Therefore, our tire above is about 8.5 inches wide.
P 215/ 75 R 15
Tire Ratio The second number is the aspect ratio. In other words, the ratio of sidewall height to width. Aspect ratio determines the profile, or how 'tall' your tire will look. It also determines the contact patch-or footprint-that your tire makes on the road. To find the height of one sidewall, multiply the tire width by the aspect ratio. For our tire above, one sidewall is about 6.3 inches tall.
P 215/ 75 R 15
Tire Type Almost all tires will have an 'R' for radial.
P 215/ 75 R 15
Wheel Diameter This is the measurement of the wheel in inches. This measurement corresponds to the rim diameter. |