These DOT date stamps are very interesting. I have heard that it is not recommended to install tires older than 3 years and that they should be discarded at 6 years! I found out that one of my cars had tires that were 10 years old which explained why they wore heavily on a little road trip. Here is an explanation of the tire dating:
"DOT codes are a 10 to 12 digit number located near the letters "DOT". BTW the digits can be numbers or letters.
The first 2 digits are a code for the manufacturing plant.
The next 2 digits are a code for the tire size.
The next 3 or 4 digits are a code for the type of tire.
The last 3 or 4 digits are the date code. The format is week/week/year/year or week/week/year
Starting in the year 2000, the date coding used is 4 digits. That means the highest number you should see for the year is 08. Before 1999 the format was 3 digits. 1999 and 2000 are transition years, so you will find both 3 and 4 digits. "
or check Tirerack at
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=11
