Mazda 3 Owner's Manual page 544

Replacing a Tire
WARNING
Always use tires that are in good condition:
Driving with worn tires is dangerous. Reduced braking, steering, and traction could result
in an accident.
If a tire wears evenly, a wear indicator will appear as a solid band across the tread.
Replace the tire when this happens.
You should replace the tire before the band crosses the entire tread.
NOTE
Tires degrade over time, even when they are not being used on the road. It is recommended
that tires generally be replaced when they are 6 years or older. Heat caused by hot climates
or frequent high loading conditions can accelerate the aging process. You should replace the
spare tire when you replace the other road tires due to the aging of the spare tire. The period
in which the tire was manufactured (both week and year) is indicated by a 4-digit number.
Refer to Tire Labeling on page 8-23 .
Tread wear indicator
New tread
Customer Information and Reporting Safety Defects
Tire Information (U.S.A.)
Worn tread
8–33