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 More info.

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.
– 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.
– The Z indicates the tire’s speed rating. (See Tire Ratings below for speed ratings.)
– R simply means that this tire is a radial.
– 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.


The temperature grades are AA (the highest), A, B, and C, representing the tire’s resistance to the generation of heat and its ability to dissipate heat when tested under controlled conditions on a specified indoor laboratory test wheel. Sustained high temperature can cause the material of the tire to degenerate and reduce tire life, and excessive temperature can lead to sudden tire failure. The grade C represents a level of performance that all passenger car tires must meet under the Federal Motor Vehicle Safety Standard. Grades AA, A and B represent higher levels of performance than the minimum required by law. The temperature grade is established for a tire that is properly inflated and not overloaded. Dr. Drivewire warns that excessive speed, under inflation, or excessive loading, either separately or in combination, can cause heat buildup and possible tire failure.

Speed Rating

Speed Ratings are key to buying the right tire and generally only appear on performance tires. Speed rating indicate that a tire is capable of handling sustained speeds up to a certain speed, assuming the tire is properly inflated and in perfect condition.

The rating Q = 99 MPH.

S = 112 MPH
T = 118 MPH
U = 124 MPH
H = 130 MPH
V = 149 MPH
W = 168 MPH
Y = 186 MPH
Z = 149 MPH and over

Performance Tires

Performance tires are those made mostly in 15 inch diameter and larger, with aspect ratios (profiles) of 35, 40, 45, 50 or 55. By using a tire with a lower profile (shorter sidewall), you gain quickness in steering response and better lateral stability. Speed ratings are generally H or greater. Most are speed rated V or Z. In general, performance tires are low profile tires with higher speed ratings and improved traction characteristics.

The goal of a performance tire upgrade is to provide improved traction and greater lateral stability, helping to increase the overall handling characteristics of the car. It also looks really cool. Performance tires are available at discount auto parts stores and online.

Plus Sizing

Plus sizing your wheels and tires is a popular and effective way to improve both the performance and appearance of your vehicle. By using a larger diameter wheel with a lower profile tire it’s possible to properly maintain the overall diameter of the tire, keeping odometer and speedometer changes negligible. The effect this has on appearance is obvious. Since wheels look better than tires, more wheel and less tire is desirable.

Maintenance and Safety

Safe tires are well-maintained tires. Well-maintained tires will last longer and give you better overall performance. Tire maintenance is as simple as it is important.

Tire Pressure

The single greatest cause of tire damage and abnormal treadwear is improper inflation. Tires can’t deliver their best performance without the right air pressure.

Check your tire pressure regularly with an accurate gauge available from any auto parts store. Also, get to know your tires. Look at them regularly when getting into and out of your car. Get used to how they look when properly inflated. That will make it easier to spot problems.

When you check air pressure, refer to your owner’s manual for the proper inflation. Although the sidewall of your tire indicates a maximum pressure figure, this number does not indicate the proper inflation for your car. It merely indicates a top pressure that you must not exceed for any reason. Find your car’s tire sticker (usually located on the door jamb or in the glove box) or refer to your owner’s manual for the correct air pressure for your tires. If you have questions, consult the manufacturer, a mechanic or a tire professional.

The tire pressure recommended by your owners manual or tire information sticker is a “cold” pressure, so it should be checked in the morning before you drive the car more than a few miles.


As your tire wears its ability to grip the road decreases. If your tires are neglected, the tread can wear completely away, leaving the surface of the tire smooth or bald. This is not only dangerous, but also illegal in many states.

When checking your tires’ inflation pressure, look for obvious signs of wear. Almost all tires have wear bars, small raised points of rubber in the grooves that show up when tires are worn out. If your tread is the same height as the wear bars, it’s time for a new tire.

Here’s an old reliable trick you can use to check the tread depth of your tires. Be sure to inspect your tire at various points. Irregular tread wear may not be readily visible.

1. Take a penny and pinch Abe’s body between your thumb and forefinger.
2. Put his head into one of the grooves of the tread at the point on your tire where tread is lowest.
3. If any part of his head is obscured by the tread, you’re driving with the legal amount of tread. If you can see all of his head, you’re ready for a new tire.

Tire Rotation…

Each tire on your car probably supports a different amount of weight, causing your tires to wear at different rates. By having your tires rotated, you can extend their life expectancy. Ideally you should rotate your tires every 5,000 to 8,000 miles, and even more frequently if you do most of your driving around town or if you own a front-wheel drive vehicle. Check your owner’s manual for proper rotation intervals.

There are several patterns you can use in rotating your tires. For instance, crossing tires from one side to another is a rotation pattern many people use. The pattern of rotation may also be dependent upon your sidewall preference (some tires have a black sidewall on one side and a white strip or white lettering on the other) and tread pattern (directional tread patterns must be rotated directionally). Which ever pattern you use, stick with it as long as you have those tires on your vehicle.


Alignment is a catchall word describing a combination of several different angles and relative positions of a wheel and tire in order for a car to roll and steer easily and predictably. Improper alignment may be felt by the car’s pulling to one side or wandering or by uneven treadwear on one or more tires. Misalignment could also result in a major repair bill if it’s not corrected. In addition to damaged tires, your car’s suspension system can be damaged. By checking your alignment every 10,000 miles, or at least once a year, your mechanic should be able to identify small problems before they become big ones.

Don’t Forget About the Spare

When you maintain or replace your tires, don’t forget about your spare tire. If you need it in a roadside emergency, you’ll want it to be there for you. Tires will lose pressure over time, and if you don’t check the spare for a year, you could be surprised and find a flat tire.

Make sure that you know where your jack is and how to use it. Your owner’s manual will give you step-by-step instructions on how to change your wheel and tire assembly. You many want to practice before you have a real need.

Safety Tips

New Tires to the Front

If you are buying only two tires from an auto parts store instead of a complete set, have the two new tires mounted on the front. If you were to have any problems with your tires, you would want to be able to steer your car through the situation. It’s better to have your best tires on the steering axle of your car.

Don’t Mix and Match

If you have to replace a single tire, make sure that at the very least it’s the same size and construction (radial or bias) as the other tire on that axle. Different manufacturers use different materials and methods of construction, so mixing brands may cause irregular wear and handling problems. Unless it is impossible, use the exact brand, model and size tire as the one you are replacing.

Repairing a Punctured Tire

Any repair done without removing the tire from the wheel is improper. Without inspecting the inside of the tire for hidden damage comes the risk of returning a weakened tire to service. Without dismounting the tire, hidden damage could be missed. Simply “plugging” a tire from the outside without removing the tire from the wheel is improper. It is only acceptable if used as a short term, low speed alternative so that you can get the tire to a shop where it can be properly inspected and repaired.

Speedometer Accuracy

Installing tires, different than your vehicle’s original equipment tire size outside diameter, may very well effect the accuracy of your speedometer and odometer. If you purchase larger tires (common for light truck and S.U.V. owners), you should verify that your speedometer is still working accurately. Overlooking this has no noticeable effect on the tires, but it can result in unwanted confrontations with your local law enforcement officials.