Buick Verano Owner's Manual page 304

Factors such as maintenance,
temperatures, driving speeds,
vehicle loading, and road conditions
affect the wear rate of the tires.
Treadwear indicators are one way
to tell when it is time for new tires.
Treadwear indicators appear
when the tires have only 1.6 mm
(1/16 in) or less of tread remaining.
See
and
more information.
The rubber in tires ages over time.
This also applies for the spare tire,
if the vehicle has one, even if it is
never used. Multiple conditions
including temperatures, loading
conditions, and inflation pressure
maintenance affect how fast aging
takes place. Tires will typically
need to be replaced due to wear
before they may need to be
replaced due to age. Consult the tire
manufacturer for more information
on when tires should be replaced.
for
Tires age when stored normally
mounted on a parked vehicle.
Park a vehicle that will be stored for
at least a month in a cool, dry, clean
area away from direct sunlight to
slow aging. This area should be
free of grease, gasoline, or other
substances that can deteriorate
rubber.
Parking for an extended period can
cause flat spots on the tires that
may result in vibrations while
driving. When storing a vehicle for
at least a month, remove the tires or
raise the vehicle to reduce the
weight from the tires.