Drivers were asked how often they normally check their tires to determine if they are properly inflated. Their answers are in the following table:

These data indicate that only about 30 percent of drivers of passenger cars, 34 percent of drivers of pick-up trucks, SUVs, and vans with P-metric tires, and 48 percent of drivers of pick-up trucks, SUVs, and vans with either LT or flotation tires claim that they check the air pressure in their vehicles' tires at least once a month.

B. Loss of Tire Pressure Due to Natural and Other Causes

According to data from the tire industry, 85 percent of all tire air pressure losses are the result of slow leaks that occur over a period of hours, days, or months. Only 15 percent are rapid air losses caused by contact with a road hazard, e.g., when a large nail that does not end up stuck in the tire punctures a tire.

Slow leaks may be caused by many factors. Tire manufacturers commented that tires typically lose air pressure through natural leakage and permeation at a rate of about 1 psi per month. Testing by CU supports those comments. In addition, tire manufacturers said that seasonal climatic changes result in air pressure losses on the order of 1 psi for every 10 degree F decrease in the ambient temperature. Slow leaks also may be caused by slight damage to a tire, such as a road hazard that punctures a small hole in the tire or a nail that sticks in the tire. NHTSA has no data indicating how often any of these causes results in a slow leak. 

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