All Those Numbers and Letters
The side of your tire may look like an ancient hieroglyphic text to you. But each of the markings stamped into the side of a tire has a meaning. Some of them will be important to you, some won't. You're probably not worried about the speed rating of the tires for your Prius, but your Porsche 997 Turbo needs go-fat rubber on the road. On the flip side, treadwear ratings are important to your hybrid, since they affect gas mileage and the effect your tires have on the environment.

The Breakdown
As technology has advanced, the tire companies agreed upon a uniform system of describing every aspect of each tire. Lucky for us, they all follow the same formula (except for race car tires which are not legal for street use.) The following categories are squeezed onto the side of every tire you can buy.

• Vehicle Application
• Tire Width
• Aspect Ratio
• Radial Designation
• Wheel Diameter
• Load Index
• Speed Rating
• The Official DOT Stuff
• Ply Construction
• Load and Pressure Limits
• Treadwear and Traction Ratings

You decide which ratings matter to you based on your car type and needs.