Came across this on a tv news show, like 60 minutes, not exactly sure which one, and it aired a year or two ago. But someone sent me an email with the relevant portion of the show. Tires have date stamps on them that tell you the week and year they were manufactured. On the sidewall near the rim find the DOT line, and at the end of that info is a box with four digits. The first two digits represent the week of the year that the tire was made: 01 to 52. The last two digits represent the year: 00 to 09. Or for the '90's, 90 - 99. The industry says tires have a safe life of six years. And the show uncovered tire retailers that were selling tires that were one, two, even three years old. An old tire can simply fail, and cause a fatal accident, as was shown in the news show. So when you buy, check the date!