Weathering and ozone cracking causes superficial cracks onthe sidewall surface around the tire circumference.
This condition is typical of tires which have
been in service for a long time.
You should check the date code on the tire.
To find the tire date code look on the
sidewall for a stamped string of letters
and numbers following the DOT.
The last four digits of the string indicate the week and year of
manufacture (e.g. 3206 would be the 32nd week of 2006).
Tire cracks can also come from exposure to ozone from
sunlight or storage next to ozone sources (e.g. electrical
equipment, air purifiers, vehicle exhaust).
According to the Tire Industry Association (TIA),
other possible causes include use of damaging tire
cleaning/dressing products, improper
inflation pressure, exposure to excessive heat, or by long
term parking when the tire is under load and deflected.
If the cracking is superficial they can be continued in
use, according to the TIA. For safety reasons, discard
tires over 6 years old or with less than 50%
remaining tread. Discard any tires wherecracking is
severe or structural material (i.e. cord) is visible
