Pontiac 1998 Grand Am Owner's Manual page 276

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:
0
T o o
much flexing
0
T o o much heat
Tire overloading
Bad wear
0
Bad handling
Bad fuel economy.
If your tires have too much air (overinflation),
you can get the following:
Unusual wear
Bad handling
0
Rough ride
0
Needless damage from road hazards.
When to Check
Check your tires
once a
month
or more.
Don't forget your compact spare tire. It should be at
60 psi (420 Wa).
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 Inspection and Rotation
Tires should be rotated every 6,000 to 8,000 miles
(10 000 to 13 000 km). Any time you notice unusual
wear, rotate your tires as soon as possible and check
wheel alignment. Also check for damaged tires or
wheels. See "When It's Time for New Tires" and
"Wheel Replacement" later in this section for
more information.
The purpose of regular rotation is to achieve more
uniform wear for all tires on the vehicle. The first
rotation is the most important. See "Scheduled
Maintenance Services" in the Index for scheduled
rotation intervals.
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