Ford 2002 Excursion Owner's Manual page 271

Replacing the tires
Replace the tires when the wear
band is visible through the tire
treads.
When replacing full size tires, never mix radial bias-belted, or
bias-type tires. Use only the tire sizes that are listed on the
Certification Label. Make sure that all tires are the same size, speed
rating, and load-carrying capacity. Use only the tire combinations
recommended on the label. If you do not follow these precautions,
your vehicle may not drive properly and safely.
Make sure that all replacement tires are of the same size, type,
load-carrying capacity and tread design (e.g., "All Terrain", etc.),
as originally offered by Ford.
Do not replace your tires with "high performance" tires or larger
size tires.
Failure to follow these precautions may adversely affect the
handling of the vehicle and make it easier for the driver to lose
control and roll over.
Tires that are larger or smaller than your vehicle's original tires may also
affect the accuracy of your speedometer.
Maintenance and specifications
271