Seemingly new tires can actually be past an "expiration date" and pose danger to those using them. Known as "aged tires", their tread can actually separate while you're driving. At highway speeds, the results have often been fatal. If you have an unused tire that's over 6 yrs old, be wary of using it, according to this link from ABC News: http://abcnews.go.com/Video/playerIndex?id=4826897