There was a news item on our local ABC affiliate yesterday on tires that reach a maximum lifespan before the tread wears out...we learned the same thing at the SMB Rally in Park City last year. (I believe it was covered on 20/20 yesterday too.) Basically, you shouldn't run any tire which is more than 6 years old. (You can read or watch the newscast story at
http://preview.tinyurl.com/6fm6z5).
The date that a tire is manufactured is given by a code on the outside of the tire. (Our BFGs came with white highlighted lettering which is on the inside and therefore the dates on our tires are on the inside.) The date should be a four-digit code...the first two numbers are the week they were manufactured and the last two numbers represent the year. Before 2000, the code consisted of only three numbers with the last number the year code. On our BFGs, the code was below the "d" in Goodrich. We replaced our tires last September and the codes indicate that they were manufactured in the 22nd and 34th weeks of 2007. So, they were already a year old when we bought them. We didn't get 6 years out of the first set of tires so I'm not worried but if you don't put a lot of miles on your van, you should check to make sure that your tires aren't exceeding the 6 year limit. As they get older than 6 years, they are more susceptible to tread separation...