Buick 1993 Skylark Owner's Manual page 245

When It% Time for New Tires
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 2/32 inch (1.6
mm) or less of tread
remaining.
You need a new tire if
You can see the indicators at three places around
0
You can see cord or fabric showing through the tire's
0
The tread or sidewall is cracked, cut or snagged deep
enough to show cord or fabric.
0
The tire has a bump, bulge or split.
the tire.
rubber.