GMC 1996 Suburban Owner's Manual page 300

After the tires have been rotated, adjust the front and rear
inflation pressures as shown on the Certificatioflire label.
Make certain that all wheel nuts are properly tightened.
See "Wheel Nut Torque" in the Index.
When It's Time for New Tires
Rust
or
dirt on a wheel, or on the parts to which
it is fastened, can make wheel nuts become loose
after a time. The wheel could come off and cause
an accident. When you change a wheel, remove
any rust or dirt from places where the wheel
attaches to the vehicle. In an emergency, you can
use a cloth or a paper towel to do this; but be
sure to use a scraper or wire brush later, if you
need to, to get all the rust or dirt off. (See
"Changing a Flat Tire" in the Index.)
L
One way to tell when it's
time for new tires is to
check the treadwear
indicators, which will
appear when your tires have
only 1/16 inch (1.6 mm) or
less of tread remaining.
You need a new tire if any of the following statements
are true:
0
0
0
You can see the indicators at three or more places
around the tire.
You can see cord or fabric showing through the
tire's rubber.
The tread or sidewall is cracked, cut or snagged deep
enough to show cord or fabric.
The tire has a bump, bulge or split.
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