To help protect your investment, properly inflated tires will provide your vehicle with great service and long life. Time and temperature are not your friend when it comes to maintaining optimal pressure. As tires are used, the rubber they're made of stretches and conforms to the road with each rotation. This stretching results in about 1 psi of lost air pressure over the course of a month. For example, if your vehicle calls for 32 psi and you do not add air to your tires over a six-month period you could lose almost 20% in air pressure.
Additionally, the fluctuation in temperature also impacts your tire's psi. The rule of thumb is for every 10 degree Fahrenheit change in ambient temperature, your tire's inflation pressure will change by about 1 psi (up with higher temperatures and down with lower). This means that a properly inflated tire at 85 degrees could lose approximately 5 psi if the temperature were to drop to freezing (32 degrees). To gain a better understanding of how temperature affects your tire's air pressure, read "Air Pressure, Temperature Fluctuations."
As you can tell, frequently checking your tire's pressure is time well spent to ensure optimal performance and wear. Proper inflation helps drivers avoid uneven wear and tire sidewall damage in extreme low pressure situations.
Maintaining sufficient air pressure is required if your tires are going to provide the handling, traction and durability of which they're capable, so take a look at the air and tread depth gauges available so you can monitor your tire's air pressure.