Rookie tire question

[schnellman]

I've done some mixing and matching in the past and didn't have any real problems. When shopping for rear replacements try to match up the UTQG, service description from the manufacturer and any other tech info you can get. Then, when you put the tires on you can use the first couple of hundred miles to get a feel for your new set up. There's nothing like the seat of your pants to match your driving to your tires and your suspension set up.

[jmatta]

First thing to do is check the date code on the fronts; it will indicate the week and year of production (WWYY format).

Reference: http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=11

If the tire is 5 years or older, it is beyond useful life and should be replaced. Plus by then it has likely turned into a hockey puck.; 23k miles on the rears...those must have been hard as rocks!