Tires: Cracks in tire tread, lincoln avaitor, climate areas

Question
Hi Barry, I have a 2004 Lincoln Avaitor with 36400 miles on the origional tires. I am the origional. Had a screw in one today and took it in for repair to a well know discount tire shop. There is still plenty of tread on the tire. The service rep said no issue to fix the leaking tire, but I should replace all 4 since there is cracks in the grooves. No cracks on the sidewalls. The truck is driven daily and we live in Las Vegas so have the extreme heat in summer. Don't want to risk a tire coming apart on the freeway or the occasion we take it on a trip. The cracks appear to be small, nothing major  that would jump out. Not a "car guy" but not an idiot either so didn't want to spend the cash to replace the tires since there is still plenty of tread, but don't want to risk a tire failure from it seperating. I hope I gave you enough info.

Thank you for your time.

Chris Page

Answer
Chris,

Recent bulletins from the tire industry indicate that tires degrade simply due to time.  The age of a tire is important even if the tire is unused.  There some disagreement over how to best express this age limitation, but my take is:

If you live in a hot climate (AZ, CA, NV, TX, and FL) then the limit is six years.  If you live in a cold climate (MN, ND, WI, MT, etc), then the limit is 10 years.  States in between are  ..... ah ........ in between.

You live in one of those hot climate areas, and your vehicle is 5 years old, so that means your tires are that old, plus some.  

The cracks are somewhat an indicator of the status of your tires.  Sounds like they are ready or nearly ready to be replaced.