DENVER (KDVR) — It’s that time of year when low tire pressure lights start to turn on and warn motorists that cold temperatures are coming and it’s time to winterize your vehicle.

It’s fundamental physics. Air molecules move slower as energy decreases with ambient temperatures, and as a result, the air pressure in tires significantly drops.

AAA Regional Director Skyler McKinley said motorists should not wait to fill up their tires for the season, as low tire pressure can become a safety hazard and affect drivability and even fuel efficiency.

“If that warning light comes on, that is your warning system saying, ‘Hey, these tires are severely underinflated,'” McKinley said. “They really are sort of the last line of defense to get you to fill up your tires.”

Low air pressure is dangerous

Because those warning lights are a safety feature, McKinley said drivers should resolve the issue as soon as possible, ideally staying on top of it before the warning light goes on. He said AAA research has found that sometimes cars light up too late.

“Even if it’s dry, if that light is on, it is still really dangerous because what happens is when you have low tire pressure the sidewalls on those tires flex excessively, that makes them heat up,” McKinley said. “That can not only accelerate tire wear but can lead to loss of tread segments or even blowouts. That’s especially true if you have low tire pressure and you hit a pothole or some other road obstacle or debris.”

When tire pressure is low, McKinley said it affects several functions of the vehicle. It can make steering sluggish and can make it more difficult for the vehicle to stop.

“Low tire pressures affect braking distances, and they are just less responsive to steering and handling. Your tires are optimized at their optimal pressure to maximize surface area and tread contact with the road,” McKinley said.

This is true regardless of the weather. McKinley said it is important to stay on top of it so drivers aren’t caught in a storm with low tire pressure or hit with the task of replacing tires when such measures could have been prevented.

On top of safety reasons, under-inflated tires can lower gas mileage by 0.3% for every 1 PSI, pound-force per square inch, that a tire is below its optimal pressure, according to the U.S. Department of Energy.

He recommends manually checking tire pressure at least once a month, ideally once a week.

How to fill up your tires correctly

The PSI of your tires should match the number specified in the vehicle’s owner manual or the number listed inside of the door jamb.

That number is the cold weather maximum, so that is what McKinley said drivers should fill tires up to when it’s cold out. It’s best to fill up your tires on a cold morning before driving a significant distance.

“When you’re driving, your tires will heat up as the rubber meets the road and your tire pressure will be more after a long drive than before one. This is fundamental physics,” McKinley said.

McKinley said tires are designed to have more leeway with overinflation as opposed to underinflation.

“The risks of overfilling your tires aren’t as dangerous as underinflating your tire,” he said.

To avoid overinflating, McKinley suggests checking the number on the tire itself.

“The numbers listed on tires are the maximum, don’t fill up to that number,” he said.

Safe winter driving

McKinley said now is the time to stay on top of winter vehicle maintenance, including tire pressure, wiper blades and snow tires.

“If you moved here from a state, like California, Florida or Texas, that doesn’t really have seasons the same way that we have seasons in Colorado, your all-season tires aren’t the right tires. Get snow tires or winter tires if you can. I understand that can be expensive and I understand a lot of folks that just don’t have the space to store an extra set of tires, in which case make sure you get all-season tires that have a mud plus snow (m + s) designation,” McKinley said. “These are chemically composed tires that are just better for the temperature variations that we see in winter.”

If you fill up your tires and the light does not turn off, McKinley recommends getting the sensors fixed because the tire pressure management system is a safety system.

He also noted that it’s important to be cautious in winter weather driving conditions regardless of how nice your vehicle is or how treaded your tires are.

“Just because you’re driving with the right tires with the right pressure in a big car doesn’t give you a license to go 20 to 40 miles an hour faster than the cars next to you. In fact, four-wheel drive does not mean four-wheel stop,” McKinley said.

Most service stations have air pumps that take credit and debit cards. However, McKinley said that if you frequently service your vehicle at a dealership or if you bought tires from a retailer, they will likely fill up your tires for you.