Things You'll Need:
- Tire pressure gauge
- Magnifying glass(maybe!)
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Step 1
The tire pressures listed on your vehicle door pillar, or glove box or trunk lid, is the pressure recommended by the manufacturer of your vehicle. It was arrived at through testing of an example of your vehicle under different loads, weather, and road types on closed & open circuits. Keeping your pressure at these recommendations will allow the vehicle to perform closely as to how it was designed to. It will accelerate, steer, and brake most effectively around these pressures. This pressure may be at or as much as 5-10psi lower than the next tire pressure listing - the one on your tires.
The PSI on the tire is the MAXIMUM pressure allowed in the tire. Exceeding it could cause improper wear patterns & increase chance of blowout.
Unfortunately the tire's listing is the pressure used by most consumers and even many reputable service garages. It is incorrect and actually reduces the contact area between your tires and the road. Also, it may stiffen/roughen the ride your vehicle is capable of giving. Steering and braking ability may be compromised also.
Always use the Vehicle Manufacturer's pressures, as mentioned above, and if these seem too soft, it's quite alright to add 1-2lbs psi to those numbers. It will help your fuel economy slightly, and the vehicle will roll better.
Very important: Do not set pressures after driving for a while. The tires(and the air inside) are hot and will give exaggerated pressure readings! My suggestion: Check/set tire pressures in the morning, when it's coolest, or at least 3 hours after a drive.
Here's a trick I use to set my pressures correctly every time.
1. On your way home, stop at a station closest to home and fill tires to maximum pressure listed on the tire. If they are hot from driving and the pressure reading is higher than max, then you will need to wait three hours or until the morning to set pressure properly. -
Step 2
2. After three hours, or the next morning, go out and check pressure. It will probably still be high enough that you will need to remove air to achieve the vehicle mfg's suggested tire pressures. That is the ideal situation, and it allows you even to lower the pressures to a pound ABOVE those recommendations, if you prefer a firmer ride.
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Step 3
3. Final rule: NEVER use your eyes to judge the inflation of a tire. Some tires look low or even overfilled depending on their speed rating & stiffness of sidewall. Only a reliable gauge will tell you exactly what's in the tire. :)
