Tires Exposed - Inside Secrets to Buying the Right Tire

  Every car sold comes with tires, right? It is hard to drive off the lot without them. The reality is that it is only a matter of time before you start giving some thought to upgrading to performance tires, or maybe you just need a new set. Does the thought of buying tires or auto parts make you as frightened as an acrophobic going to the top of Sears Tower? Calm down. Take a deep breath because Dr. Drivewire will explain all of the insider secrets you need to know about purchasing the best tire for your needs.

In two short minutes you'll have your masters in tireology. You will have all the skills you need to pour through the product specifications, eliminate the middle man and buy with confidence from a secure online store. Premiere online retailers offer off dealer pricing, real time inventory, free shipping and rush delivery.

Reading the Sidewall

The side of your tire contains a wealth of information. Here's an example of a tire sidewall, in this case a Bridgestone Potenza S-02 P205/55ZR14

a - The brand or model of tire.

b - This is a tubeless tire. Almost all tires today are tubeless.

c - The arrow on the tire indicates that the tire is unidirectional and must be mounted so that the arrow points toward the front of the car.

d - "P" means passenger tire.

e - Indicates how wide the tire is in millimeters. Also referred to as section width.

f - The tire's aspect ration, or profile. Basically, how tall the tire is. The number is actually a percentage of the width. This tire is 55% as tall as it is wide.

g - The Z indicates the tire's speed rating. (See Tire Ratings below for speed ratings.)

h - R simply means that this tire is a radial.

i - The diameter of wheel that this tire is intended to fit. In this case 14.

Tire Ratings


Consumer magazines, tire retailers and Dr. Drivewire frequently use the UTQG ratings when comparing tires. The initials stand for Uniform Tire Quality Grading, a quality rating system developed by the Department of Transportation (DOT). The system was designed to provide information to consumers as to the relative performance of passenger tires in the areas of treadwear, traction and temperature. The UTQG ratings are most valuable when comparing how a manufacturer's tires rate within its own product line rather than as a comparison between brands. UTQG is just one tool to use when selecting tires and it should not be your only guide.

A UTQG Auto Parts Tire Rating Looks Like This: 150 A B

The number 150 indicates the treadwear rating.

The first letter (A) indicates traction rating.

The second letter (B) indicates temperature rating.


The treadwear grade is a comparative rating based on the wear rate of the tire when tested under controlled conditions on a specified government test course. For example, a tire graded 150 would wear one and a half (1 1/2) times as well on the government course as a tire graded 100. Regardless of what kind of UTQC treadwear grade a tire may get, actual performance will vary significantly based on driving habits, maintenance and differences in road conditions.


The UTQG traction grade is based on a straight ahead braking traction test. It is not based on cornering traction. The traction grades from highest to lowest, are A, B, and C. They represent the tire's ability to stop on wet pavement as measured under controlled conditions on specified government test surfaces of asphalt and concrete. A tire marked C would be considered a poor traction tire.