1997 Pontiac Grand Prix Owner's Manual - Page 316

I NOTICE: Don't let anyone tell you that underinflation or overinflation isall right. It's not. If your tires don't have enough (underinflation), you can air get the following: 0 Too much flexing 0 Too much heat 0 Tire overloading 0 Bad wear Bad handling Bad fuel economy. If your tires have too much air (overinflation), you can get the following: Unusual wear Bad handling Rough ride Needless damage from road hazards. When to Check Check your tires once a month or more. Don't forget your compact spare tire. It shouldbe 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 leaksby keeping out dirt and moisture. 6-46