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I have a set of Michelin 235/16 motor home tires that are 16 years old and used only 15000. Only in the weather while actually driving. They look good and no signs of dry rot. Are they safe?  

First, "shelf life" implies unused tires - and you obviously are talking about tires in service.

Second, 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 is 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 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.

If you want more detail on the coding system:

http://www.barrystiretech.com/dotcoding.html  

hi at 16 year old you would be best taking them to a museum .i would not risk using them on your vehicle the normal tyre age is 6 years and bellow. thanks  eric roberts  old tyre problem