Tires: Travel Trailer Tire selection, fleetwood travel trailer, bias ply tires

Question
I have a 30' fleetwood travel trailer. Loaded gross wt is approx. 9500 lbs. It currently has ST225/75R/15 tires on it. The tires are showing cracks on the sidewalls which I assume is due to age and not being used a lot before I bought it. I had a flat on our last trip and had to replace the flat with a matching radial. I came across a set of four ST225/7515 bias ply tires with 3000 miles on them for $60.00. What is your recomendation for tire replacement? Go with the bias ply deal and use the new radial as a spare or would I need a bias ply spare?

Answer
Robert,

The general rule is that radials and bias tires should never be mixed.  Obviously there are situations where "You can get away with it."

So I would make sure that all tires on the ground are of the same type - and would even go so far as say they ought to be the same brand.  This is to minimize the differences between the amount the tire deflects and, therefore, the differences between what load the tire actually carries.

You should also be aware of the Load Range.  I'm guessing that these are all Load Range D - 2540# at 65 psi - but you should check to make sure.

Plus, 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 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.