the DOT number on the tire shows the production date. In pennsylvania
state vehicle inspection mechanics are supposed to check all tirees
nymbers and reject any that are too old. I will ask a inspection buddy
but I beeve it 6 to 8 years. these rules started after some accidents
caused by aged tires shredding and deaths.

by 10 years outdoors tires are junk, I replaced some trailer tires and
a buddy has cars that get little use, like a few thousand miles a
year.

He was forced to replace the tires at 10 years, and remarked the tires
sun shined on were much worse.