Q: The pressure in my tires changes from when I park inside my heated garage to when I check them outside in the cold weather. What is going on here?
A: Generally, a tire’s air pressure changes 1 psi (pounds per square inch) for every 10 degrees Fahrenheit (F) change in temperature. The air pressure goes up when the temperature increases and goes down when the temperature decreases. For example, if you have your car parked in a heated garage at 70 degrees F and then drive your car when it is 0 degrees F outside your tires may be as much as 7 psi too low. If you are checking the tires inside the warm garage, you need to adjust the tire pressure for what the temperature is outside. To do this, you need to add 1 psi for every 10 degrees F difference between the garage and outside.