1999 Pontiac Grand Am Owner's Manual - Page 258

yellowblue When to Check NOTICE: Don't let anyone tell you that underinflation or overinflation is all right. It's not. If your tires don't have enough air (underinflation), you can get the following: D Too much flexing D Too much heat D Tire overloading D Bad wear D Bad handling D Bad fuel economy. If your tires have too much air (overinflation), you can get the following: D Unusual wear D Bad handling D Rough ride D Needless damage from road hazards. Check your tires once a month or more. Don't forget your compact spare tire. It should be at 60 psi (420 kPa). How to Check Use a good quality pocket-type gage to check tire pressure. You can't tell if your tires are properly inflated simply by looking at them. Radial tires may look properly inflated even when they're underinflated. Be sure to put the valve caps back on the valve stems. They help prevent leaks by keeping out dirt and moisture. Tire Pressure Monitor System (If Equipped) The tire pressure monitor system can alert you to a large change in the pressure of one tire. The system "learns" the pressure at each tire throughout the operating speed range of your vehicle. The system normally takes between 45 and 90 minutes of driving to learn the tire pressures. This time may be longer depending on your individual driving habits. Learning need not be accumulated during a single trip. Once learned, the system will remember the tire pressures until the system is recalibrated. 6-36