Did you see a strange warning light on your dashboard as you shivered into the driver’s seat this morning?
If it looks like an exclamation point between parentheses, it means your tire pressure is way too low. Like other gases, air contracts as it gets colder — and that means there’s less pressure in your tires.
Tire pressure (per square inch) drops between 1 and 2 pounds for every 10-degree decrease in temperature, and that can make a big difference to a driver who hasn’t filled up since summer.
When the temperature hits 25 degrees, for instance, your tires could be 5 to 10 pounds per square inch lower than they were on a 75-degree morning last summer.
So even if you filled up to a comfortable PSI of 32 in August, your tires could have dropped by 25 percent or more on a cold winter day — which in most cars is enough to trigger a warning.
Tire manufacturers say the onset of winter weather is a good time to make sure your tires are properly inflated. Air pressure can affect steering, handling, gas mileage, and the life of the tires themselves.
“If you simply use [the light] that as a crutch to say, ‘Hey, I need to put air in my tires,’ then you’re already down a certain threshold,” Jim Davis, a spokesman for the tire maker Goodyear, said in a 2014 interview. He suggests that people check in using a pressure gauge once a month or before any big trip.
Every vehicle has its own ideal PSI. It’s usually written on the driver’s side door jamb, and in the owner’s manual.
That rating might not be the same as what’s listed on the wall of the tire, which is the maximum amount of air it can hold, rather than the best amount for your particular car. It also might be the difference between an unexpected flat and a smooth ride.
Your tires are the only part of your vehicle touching the road. Try to keep it that way.Andy Rosen can be reached at firstname.lastname@example.org. Follow him on Twitter @andyrosen.