Tires: Tires size, chevy vans, 4 digits

Question
Currently I have LT265/75R16 tires on my 1989 Chevy utility van (duals in rear).  A friend of mine gave a set of rims and tires he said would fit the vehicle.  The tires on those rims are 7.50R16.  Is there a major difference in tires?

Answer
Richard,

There is a lot of conflicting information in your post.

Chevy Vans never came with dualled rear wheels except for cutaways and I don't have any information on those.

However, Chevy Pickup Duallies of that era came with LT225/75R16's - which means the rims were 6" wide and had a dual spacing of 10.2".  An LT265/75R16 requires a minimum rim width of 7" and a minimum dual spacing of 12.2".

Earlier versions of Chevy duallie pickups did come with 7.50-16's on 6" rims with a dual spacing of 10.0".  

So not only does it sound like the rims you were given don't have enough dual spacing, it also sounds like your current rims are not suited for the LT265/75R16's on them.

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 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.