If you set your tire pressure to the number stamped on the sidewall, your tires are overinflated. That number — usually 44, 50, or 51 PSI — is the maximum the tire is rated to safely hold, not what you should run. The correct pressure for your specific vehicle is somewhere else.
Where to find the right number
Open the driver's door and look at the door jamb. There's a yellow-and-white placard listing the recommended cold inflation pressure for the front and rear axles. For most passenger cars, this is 30 to 35 PSI. SUVs and light trucks often run 33 to 38 PSI.
Why the door jamb wins
The vehicle's engineers determined the right pressure for your car's specific weight, suspension geometry, and the tire size it comes with from the factory. The number on the sidewall is set by the tire manufacturer for the tire alone, with no knowledge of which car it's mounted on. The door jamb is calibrated to the whole system.
What 'cold' actually means
Cold inflation means the tire has been parked for at least three hours, or has been driven less than a mile. Heat builds pressure — a tire that's been driven on the highway for 20 minutes will read 3 to 5 PSI higher than the same tire cold. Always check and adjust pressure cold.
Pressure changes with temperature
Tire pressure drops about 1 PSI for every 10 degrees Fahrenheit drop in temperature. A tire set to 35 PSI on a 70-degree fall day will read 30 PSI on a 20-degree winter morning. This is why TPMS lights tend to come on the first cold morning of the year.
Symptoms of underinflation
- Outer-shoulder wear on both edges
- Worse fuel economy (1-3% per 5 PSI low)
- Slow, mushy steering response
- Heat buildup that can cause tread separation at highway speed
Symptoms of overinflation
- Center-tread wear in a stripe down the middle of the tire
- Harsher ride
- Reduced wet traction (smaller contact patch)
- Increased risk of impact damage on potholes
How often to check
Once a month, cold. More often in fall and spring when temperature swings are large. A $10 pencil gauge is more accurate than the gauge on most gas-station air machines.
Door jamb, not sidewall. Cold, not warm. Once a month, not once a year.