Ford 2002 Focus Owner's Manual page 319

Maintenance and Specifications
Replacing the tires
Replace 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 and
tread design (e.g., All Terrain",
etc.), as originally offered by
Ford.
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.
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