Tires: tire dry rot, rubber degradation, tire dry rot

Question
I own a 2004 explorer with 34,000 miles. i was told i needed new tires because my tires have dry rot.  i live in Massachusetts.  i just replace the brakes in the truck and i was told it is because i do not drive the truck enough. now same with the tires.  my truck has been towed to ford maybe 15 times because i was again told i did not drive it enough in the first three years i owned it.  After they replaced the third new battery the truck was fine. sorry to go on, my question is:  the sidewalls of the tires are fine , between the threads there are small cracks on all four tires, i am not sure if i need to replace the tires or not?

Answer
Robert,

Assessing cracks in tires is difficult without seeing them in person.  But you should be aware that cracking is a normal part of rubber degradation.  Some cracking is to be expected.

If the cracks were on the surface of the tread, rather than in the grooves like your case, this would be cause for removal.

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.

Here's how to tell how old the tires are:

First locate the letters "DOT" on the sidewall of the tire.  Nearby will be the DOT code.  DOT codes are 10 to 12 digits long.  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.  These are always numbers.

Starting in the year 2000, the date coding used was 4 digits.  That means the largest number you should see for the year code is 09.  Before 1999 the format was 3 digits.  1999 and 2000 are transition years, so you will find both 3 and 4 digits.

The date code only has to be on one side – and it is permissible for there to be a partial DOT code, so long as one side has the complete code.

It is likely that your tires are 5 or 6 years old.  You do not live in one of "those" areas, so you can use the 10 year limitation.

I suggest you locate a tire dealer you can trust and have him look at the tires.