Saturn 2007 Ion Owner's Manual page 310

Brake Wear
Your vehicle has front disc brakes and rear drum
brakes or rear 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 Saturn
specifications.
The rear drum brakes do not have wear indicators,
but if you ever hear a rear brake rubbing noise,
have the rear brake linings inspected immediately.
Also, the rear brake drums should be removed
and inspected each time the tires are removed for
rotation or changing. When you have the front
brake pads replaced, have the rear brakes
inspected, too.
Brake linings should always be replaced as
complete axle sets.