What Causes Low Tire Pressure in Winter?

It's inevitable – your car tires will lose air pressure during the winter. Here’s why it happens.
low winter tire pressure

A dead battery. Snow, ice and salt buildup. Frozen door locks. Many of winter’s harmful effects on your car are readily apparent. Others, however, you may not notice until it’s too late. Such is often the case for one of the most prevalent issues motorists must contend with during the colder months: low tire pressure.

There’s no way around it – your car tires will lose air pressure at a faster rate when the cold weather arrives. Here’s what causes low tire pressure in the winter, why under-inflated tires cause a serious safety risk and how to best keep your tires in fair shape during the foul-weather season.

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What Causes Low Tire Pressure in the Winter?

The simple answer to this question is cold temperatures. As you may remember from grade school science classes, when a substance is cooled, its molecules slow down and move closer together. In other words, the substance becomes compact and dense.

This same principle causes low tire pressure in the winter. As the temperature drops, the air molecules condense and exert less pressure on the walls of the tire.

As a general rule, a tire will lose 1 pound per square inch with every 10-degree drop in temperature. This is in addition to the 1-2 psi tires typically lose each month from normal, everyday driving.

The Dangers of Low Tire Pressure

Low tire pressure can be expensive – it causes fuel inefficiency (which will cost you at the pump) and premature tread wearing (which means forking over money for a new set of tires). But driving with underinflated tires isn’t just a financial drain, it’s a serious safety hazard. Low tire pressure makes it more difficult to steer and stop, which can easily contribute to a crash. A worn-down tire is also more prone to punctures that will leave you with a flat.

Most notably on the safety front, low tire pressure can cause a blowout. When a tire is underinflated, more of its surface comes in contact with the road. This increases friction that, in turn, causes a buildup of heat. If the air inside a tire gets too hot, a portion of the rubber wall can pop loose. The sudden rupture causes an immediate and rapid loss of air. Blowouts are extremely dangerous as they can cause you to lose control of your vehicle and force other drivers to deal with a flying piece of debris.

When to Check Tire Pressure in Winter

The aforementioned dangers can all be prevented by taking the simple step of checking your tire pressure more often in the winter. Nowadays, most cars have tire-pressure monitoring systems that alert drivers via dashboard light when the tires are under inflated. But it’s best to keep your tires inflated rather than wait until they are underinflated.

You should be checking your tire pressure at least once a month throughout the year. During the winter, however, you’ll likely need to double the frequency. To get the most accurate reading, check your tire pressure using a high-quality air gauge in the morning or after the car has been idle for several hours. Tires and the air inside them will get hot when in use, causing the air to expand and pressure to increase. You need the tires to be cold to prevent a false reading. If the low-pressure light comes on when you start your car but goes away once you begin driving, you still have underinflated tires.

Compare the reading with the manufacturer’s tire pressure recommendation, which can be found in the owner’s manual and on the driver’s-side doorjamb. Once your tires are inflated to the recommended level, you’re good to go!

Winter is one season not to be trifled with. Learn how to prepare your car and stay safe on the road during the cold-weather months.

Even a properly inflated tire can suffer damage. Keep them protected during all four seasons by enrolling in AAA’s Tire & Wheel Protection Program.

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3 Thoughts on “What Causes Low Tire Pressure in Winter?

  1. My vehicle tire pressure indicator light kept coming on in the mornings, after frigid nights. Upon inspection by my mechanic, he determined that where the valve stems (and pressure sensors) were inserted into the wheel rims there was corrosion–probably due to the salt on the roads (to control ice in winter)–maybe there were also dissimilar metals in contact with each other. After replacing the pressure sensors on the whee rims, the problem ceased.

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