Chevrolet 2007 Express 2007 Express Owner's Manual page 324

Brake Wear
Your vehicle has four-wheel disc brakes.
Disc brake pads have built-in wear indicators that
make a high-pitched warning sound when the
brake pads are worn and new pads are needed.
The sound may come and go or be heard all
the time your vehicle is moving, except when
you are pushing on the brake pedal firmly.
CAUTION:
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The brake wear warning sound means
that soon the brakes will not work well.
That could lead to an accident. When
you hear the brake wear warning sound,
have your vehicle serviced.
Notice: Continuing to drive with worn-out
brake pads could result in costly brake repair.
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Some driving conditions or climates may cause a
brake squeal when the brakes are first applied
or lightly applied. This does not mean something
is wrong with your brakes.
Properly torqued wheel nuts are necessary to help
prevent brake pulsation. When tires are rotated,
inspect brake pads for wear and evenly tighten
wheel nuts in the proper sequence to GM torque
specifications.
Brake linings should always be replaced as
complete axle sets.
Brake Pedal Travel
See your dealer if the brake pedal does not
return to normal height, or if there is a rapid
increase in pedal travel. This could be a sign
of brake trouble.
Brake Adjustment
Every time you make a brake stop, your disc
brakes adjust for wear.