The car maker and tire makers are disputing each others' claims about tire life expectancy. Ford, who got a black eye through the Explorer rollover problems (and may get another one due to roof strength) is urging customers to toss tires with plenty of tread life if the tires are older than 6 years. Ironically, the tire companies say otherwise. You'd figure someone in the sales department would say "Hey, that'd sell more tires!" But they insist that 10-year-old tires are just as good as new ones. Ford now joins many European car makers and Toyota in recommending a 6-year expiration date on tires.