Once a month, plus any time the weather turns. Cold air alone can take a tire from fine to low overnight.
Check your tires once a month, and again whenever the temperature swings by 10 degrees or more. Air contracts as it cools, and a tire loses about 1 psi for every 5 to 6°C the temperature drops. A tire you set on a 25°C September afternoon can read 5 psi low on the first frosty morning in November.
Your vehicle's recommended pressure is on a sticker inside the driver's door. The number molded into the tire's sidewall is the most that tire can safely hold, which is higher than you want for daily driving.
Driving warms the air inside a tire and pushes the reading up. Check in the morning before you drive, or after the car has sat for three hours.
Cold readings are the true readings.
A heated garage fools you the other way. Set the tires to spec at 15°C and then park outside at -15°C, and by morning they'll read about 5 psi low.
On most newer vehicles, the tire pressure light comes on when a tire is about 25 percent below its recommended pressure. For a tire that should sit at 35 psi, that's around 26 psi. Grip and fuel economy start slipping long before that.
Some winter wheels have no pressure sensors, and on those the warning light stays on all season. A gauge in the glovebox becomes your only real warning.
Watch for these:
A tire that needs air every week has a slow leak, most likely a nail in the tread or a tired valve. Most nails in the tread can be repaired, for about $40. TPMS or valve service runs about $25. Our repair guide covers what can be fixed.
Keep a gauge in the glovebox and check all four on the first frosty morning, plus the spare if you carry one.
Last updated: September 2026
Once a month, and again whenever the temperature swings by 10 degrees or more. Check before a long drive too.
About 1 psi for every 5 to 6°C drop. A 30-degree swing from a warm fall afternoon to a frosty morning can take 5 psi out of every tire.
The number on the sticker inside the driver's door jamb. The number on the sidewall is the most the tire can hold, which is higher than you want for daily driving.
Set them to the door-jamb number while the tires are cold, then recheck after each big temperature drop. That usually means topping up a few times between November and February.
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