It happens every year around this time. You walk out on a 35 degree morning, start the car, and the tire pressure light is on. You look at all four tires and none of them look low. By lunch the light is off again.
Nothing’s broken. It’s physics, and it’s one of the most common calls we get once fall shows up in the Valley.
Cold Air Takes Up Less Space
Tire pressure drops as the temperature drops, roughly one PSI for every 10 degrees. Here it’s normal to see a 40 degree swing between a September afternoon and the next morning. That can take a tire from 35 PSI down to 31 overnight, which is right about where most tire pressure systems start warning you.
Once you drive a few miles, the tires warm up, the pressure comes back, and the light shuts off. So the light wasn’t wrong. Your tires really were low that morning.
Why It Matters Even When the Light Goes Away
It’s easy to ignore a warning that fixes itself. But a tire that runs a few PSI low every morning all winter wears out faster on the outer edges and gives up grip on wet or icy pavement. On a loaded truck, or a car headed up 55 to McCall, that difference is real.
How to Set Your Pressure Right
Use the number on the sticker inside your driver’s door jamb. Not the number on the tire sidewall. The sidewall number is the most that tire can safely hold, not what your car is designed to run.
Check it cold, before you’ve driven more than a mile or two. If you drive across town to a gas station and check there, you’ll get a high reading and end up underinflated.
Once the cold mornings settle in, top the tires off to the door sticker number. You’ll probably need to do it again in December.
When It’s Not Just the Weather
If the light stays on after 15 or 20 minutes of driving, or one tire keeps losing air faster than the others, something else is going on. What we usually find:
- A nail or goathead thorn in the tread
- A bent wheel or leaking bead from a pothole or curb
- A leaking valve stem
- A TPMS sensor with a dying battery
If the light flashes for a minute when you start the car and then stays on, that usually means a problem with the system itself, not low air.
Swing By
If your light is acting up, bring it in for a free tire check. We’ll find out whether you’ve got a leak or just a cold snap, and we’ll tell you which. Call (208) 559-8492 or stop by 19945 Middleton Road in Caldwell. Walk-ins are always welcome.
