A perfectly normal tire, inflated with 35 pounds per square inch (psi) can lose 1 psi each month because of natural tire permeability.
Check all four tires at least once a month and before a long trip. (Some professional drivers are required to check tire pressure every day!)
Always check tire pressure when the tires are cold. This usually means before driving more than one or two blocks at less than 30mph or 50kph.
Check your spare tire pressure too. Many experts suggest keeping the spare pressure at one or two pounds higher pressure than normally used on your vehicle. (It's easier to let air out than to increase pressure in an emergency.)
The recommended pressure for your tires are those listed by your vehicle's manufacturer.
Recommended pressure can be found:
DO NOT use the pressure stamped on the sidewall of your tires - that's the Maximum Pressure for which the tire is designed. If you're even thinking of using a greater pressure, then you need to use a tire designed for a pressure which exceeds the amount you wish to use.
Be wary of pressure gauges at gas stations. They are often abused and cannot be considered reliable.
Purchase a good pressure gauge and check it for accuracy with your tire dealer.
Check your tires cold - before you've driven even one mile or at least three hours after the vehicle has been stopped.
Air expands when it's heated and contracts when it's cooled.
Even in cold weather, the air in a tire becomes warmer and pressure increases as the tire is driven.
High speed or highway driving can heat a tire to the point where it is uncomfortable to touch with your bare hand.
The best time to inflate your tires is in the morning before the day's heat or driving heats up a tire.
Your tire's valves are very important maintenance items for proper tire pressure. Because valves are ordinarily made of rubber they can deteriorate over time. Replace them when you buy new tires. At highway speeds, a cracked or deteriorated rubber valve stem can bend from centrifugal force and permit air loss.
The valve cap is also an important item. A high-quality valve caps can help maintain the tire's air, if the valve core fails for any reason. Valve caps also keep out moisture, which could freeze and in turn depress the valve core, causing air loss. The cap also keeps out dust and dirt particles, which could also interfere with the proper operation of the valve core and cause air loss.
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