Cool weather and tire pressure: Protect yourself

Proper inflation of your tires is essential during the cold winter months.

The cooler temperatures can cause the air in your vehicle's tires to contract and thus make your tire pressure fluctuate. Tires need to have proper grip to the pavement so that you, as the driver, can control the vehicle.

A tire that is grossly underinflated can separate from the wheel rim, causing an accident. An underinflated tire creates friction that can cause the tread to separate and the tire to fail. Underinflated tires also wear more quickly and burn more gasoline.

You should check your tire pressure more often in the winter months. Less sunlight and colder ambient temperatures will reduce your tire pressure about 1 pound per square inch (PSI) for every 10-degree Fahrenheit change in the thermometer.

That is, if you last checked your tires on a 70-degree summer morning, they could lose 3 psi when the temperature drops to 40.
How to set tire pressures
The tires on your car should be set to the pressures listed in your owner's manual or on the door edge.You may find recommended "cold" pressures; that means you should set the tire to this pressure before the car has been driven, which warms and expands the air inside the tire. You may also find maximum allowable pressures listed. An overinflated tire can lose grip and wear unevenly.

Vehicles built since 2007 include tire pressure monitoring systems (TPMS) as standard equipment, a safety feature required by the federal government. At minimum, your car should provide an alert if one or more of your tires falls below a minimum tire pressure. Some cars offer a real-time readout that displays the current tire pressures at each corner of the car.
TPMS is an important safety feature, but do not expect an insurance discount for cars so equipped. (See how your choice of car affects your car insurance and discounts.)
While TPMS alerts a driver to pressures that have fallen into a dangerous zone, you should check tires regularly even without a warning light. Tire pressure gauges are readily available and inexpensive; a digital or dial gauge will be more reliable and easier to read than an old-fashioned pen-style gauge. You'll see these benefits:

    A properly inflated tire improves gas mileage. The U.S. Department of Energy estimates that underinflated tires waste 2 billion gallons of gasoline a year.
    A properly inflated tire wears more slowly. If you see tires wearing on their edges but not at their centers, your tires are underinflated. Conversely, worn centers are a sign of overinflation.
    A properly inflated tire is safer. Your car is putting more rubber on the pavement, which means handling is more secure and braking is more stable.

Many people tend to forget to check their spare tire as well; check the spare when you change your oil and you'll avoid an expensive road-service claim.

As read on: http://www.carinsurance.com/Articles/content197.aspx