Despite all the recent hoopla about keeping your tires inflated, new research shows that most drivers are checking their tire pressures -- without knowing the correct inflation level. According to the AAA Foundation for Traffic Safety, 51 percent of American drivers check their own tire pressure. Unfortunately, 48 percent of those surveyed consult the tire sidewall, which indicates maximum tire pressure.

Bill Egan, Goodyear chief engineer of advanced product design, said the correct tire inflation isn't a multiple-choice answer. "We stress the importance of proper tire inflation without specifying the correct level," Egan said.

Part of the problem, Egan said, is that the answer varies with application and the load to be carried.

Tire inflation to tires is like oil to a vehicle's engine; the correct inflation determines the tire's load-carrying capacity for optimal tire deflection, thus maximizing handling, treadwear and ride as well as reducing rolling resistance and ensuring durability by reducing the stress-strain level that allows the tire to run cooler, Egan said.

That makes the specially formulated inner liners engineered into some tires doubly important for helping tires to hold air. Unfortunately, not all tiremakers use 100 percent concentrations of halogenated butyl rubber -- the best choice for air pressure impermeability -- to help protect the integrity of a tire's internal components, Egan said.

The Society of Automotive Engineers reports that 87 percent of all flat tires have a history of underinflation. Tires without these special inner liners can lose twice as much inflation in a year -- up to 15 pounds per square inch.

Halogenated butyl rubber, when used, is the most expensive material in a blackwall tire. "To omit it or to use it in less than 100 percent concentrations saves money," Egan said. "However, as a way to retain air in your tires, it's a case of being a penny wise, and a pound foolish."

According to the AAA tire safety survey, few checked for the correct inflation pressure that related to their specific vehicle, such as by looking in the owner's manual -- 27 percent -- or at the tire inflation sticker on the vehicle's door jamb -- 18 percent.

Most American drivers -- 82 percent -- say their inflation pressure gets checked regularly, at least once every three months, with 48 percent getting it checked at least once a month.

Goodyear recommends that motorists check tire pressure monthly, before a long trip or when the outside air temperature changes significantly. If the car is carrying extra weight, such as luggage on a vacation, additional air should be added to the tires, preferably 4 psi over the vehicle manufacturer's recommended cold tire pressure, or that which is specified in the owner's manual or on the door jamb (not to exceed the maximum on the tire sidewall), Egan said.

Among the 51 percent of Americans who check their own tire pressure, 86 percent use their own tire gauge, the AAA study indicated. The remainder practice far less reliable methods, such as the 13 percent who use a service station gauge, the 8 percent who simply look at the tire and the 3 percent who thump the tire with a tool.

Barring the use of their own tire pressure gauge, Egan said motorists may receive a free tire inspection check and free air at their local Goodyear retailer which can be found by calling 1-800-Goodyear, or by visiting the company's Web site at www.goodyear.com .