There is a lot of information on the sidewall of a tire. Typically, you'll find UTQG ratings for treadwear, traction and temperature, the size of the tire, the load rating index number with a speed rating index, the construction type (bias or radial), the D.O.T. (Dept. of Transportation) compliance code, construction details, and of course, the make and model of the tire. On some tires used as Original Equipment, you may also find a marking that indicates its OE status. Porsche uses an N-0 or N-1 designation, BMW uses a star on some O.E. tires and General Motors uses a "TPC" code. Light Truck tires are sometimes marked with an LT for "Light Truck" before the size, passenger tires are often marked with the letter P for "Passenger" before the size. Passenger tires of the same size with or without the P are virtually interchangeable .

Vehicle manufacturers understand that there is little reason to spend millions of dollars developing the ride and handling qualities of a new vehicle's suspension if they are going to omit integrating the influence of its Original Equipment tires. This has resulted in either completely new tire designs or fine-tuned versions of existing designs being engineered for every new car and light truck from the beginning of the vehicle's development process.

There was a time in America when it was thought that the only reasons a vehicle manufacturer chose Original Equipment tires were "how wide were the whitewalls" and "which manufacturer would sell their bias ply tires for the lowest price." Well even if that had been true, times have changed and neither whitewalls nor cheap bias ply tires are used on vehicles today.

Part of the reason for this is because tire comfort and tire performance directly correlate with the driver's overall vehicle satisfaction. Original Equipment tires play an integral role in achieving the vehicle's desired comfort and performance capabilities, and greatly influence the vehicle's personality. And as vehicles have evolved, so have OE tires. For the most part, today's vehicles are lighter, more fuel-efficient and more responsive than those built a decade ago. This has caused corresponding reductions in tire weight and rolling resistance, while enhancing the tire's handling capabilities.

Unfortunately even the best tires are still a compromise. This is because the current materials and manufacturing technologies that provide many desirable tire attributes are directly opposed to other desirable attributes. For example, a "hard" tread compound that could provide long wear and low rolling resistance would also reduce traction. An "aggressive" tread design that could better resist hydroplaning or provide enhanced snow traction would also generate more noise. And a "stiff" sidewall that could provide responsive handling and high-speed stability would also reduce ride comfort. These opposing goals require blending and balancing the tire's comfort and performance traits until they are optimized for the OE tire's intended vehicle application.

Each vehicle manufacturer prioritizes the areas that they feel are of greatest benefit to help their vehicles satisfy their drivers. For example, a vehicle manufacturer that offers a line of fuel-efficient vehicles may be able to place more emphasis on traction and less emphasis on lowering rolling resistance than a vehicle manufacturer that builds a line of larger, less fuel-efficient cars.

A tire's characteristics can be represented graphically in a "spider" chart (see below). These charts provide a visual means of presenting multiple performance characteristics to allow direct comparison of an existing tire's capabilities (usually established at the 100 level as a baseline) to the targets and/or realized performance levels for a new tire.

While the tire manufacturer's ultimate goal is to develop technology that allows them to expand the new tire's entire comfort and performance envelope in all directions compared to the original tire, frequently they are only able to expand the tire's capabilities in several areas without causing compromises that would result in less performance in other areas. This type of analysis allows confirmation of the accomplished improvements and any resulting compromises.

Starting from the same original tire would result in identifying different goals for a tire intended for a luxury coupe vs. a tire intended for a true sports car. Which is the better tire? In reality, neither of them is better; but they are both different. Most importantly, both would be tuned to meet the desired personality of the car. However, if misapplied, the driver would experience a loss of performance if the luxury coupe tire was installed on the sports car, or a loss of comfort if the sports car tire were installed on the luxury coupe.

Only the vehicle manufacturer and tire manufacturer working together to develop the OE tire can determine exactly which tire design and internal construction will produce the most satisfactory results. A tire manufacturer who builds "all-purpose" replacement tires will never receive the benefit of the vehicle manufacturer's insight and intent, and is relegated to producing "average" tires.

Does it really make a difference?

Since 1990, J.D. Power and Associates has conducted an annual Original Equipment Tire Satisfaction Study to report on how consumers rate their satisfaction with Original Equipment tires on their one-, two- or three-year-old vehicles. The study conducted in 2002 was based on the experiences and opinions of more than 33,700 drivers. The study includes a nationally representative sample of all makes and models of passenger cars, vans, pickup trucks and sport utility vehicles sold in the U.S.

The study monitors consumer perceptions regarding tire quality, performance, brand image and service. Results are calculated using a tire satisfaction index that includes five factors: product quality, long-term performance, situational performance, design and winter traction. The 2002 study found Michelin brand products achieve the highest tire index score with passenger car and light truck drivers.

Maintaining high customer satisfaction is key to vehicle and tire manufacturers alike. Vehicle manufacturers benefit from higher vehicle satisfaction ratings, and tire manufacturers that have high levels of driver satisfaction also have the highest percentage of drivers who report that they intend to buy that same tire brand in the future. Among year-one owners, more than 60 percent of the drivers on OE Michelin report that they plan to repurchase Michelin tires in the future, the highest repurchase intention of all tire brands.

Example...185/60R14 85H or 185/60HR14

185mm x .60=111mm x 2=222mm + 355.6mm(14")= 577.6mm or 22.74"

The first number is the width of the tire in millimeters, measured from sidewall to sidewall. To convert to inches, divide by 25.4 In the example above, the width is 185mm or 7.28".

The second number is the aspect ratio. This is a ratio of sidewall height to width. In the example above, the tire is 7.28" wide, multiply that by the aspect ratio to find the height of one sidewall. In this case, 185x0.60=111mm or 7.28"x0.60=4.36".

The last number is the diameter of the wheel in inches.