Ford Windstar Owner's Manual page 305

Maintenance and Care
Rotating the tires
If your vehicle has the optional full-size spare tire, you may
rotate the spare tire into the rotation pattern.
If your vehicle has aluminum wheels, you may remove the
full-size (if equipped) spare tire from the wheel and remount it
on an aluminum wheel to rotate the spare tire into your
vehicle's rotation pattern.
Replacing the Tires
Replace tires that show wear bands. When your tire shows a
wear band, it has only 1/16 of an inch (1.59 mm) of tread left.
A worn-out tire
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