Tires: 7.50 R16 LT tires v. 245 75 R16, rim width, side clearance


Question
was wondering what the difference is between these types of tires. I have a gooseneck trailer with the 7.50 R16 and a 3/4 ton truck with the 245 75 R16 tires on it. Both types are LT and E load rated. I was thinking of buying new tires for the 3/4 ton truck and putting the current, slightly worn, truck tires (the 245 75 R16's) on the gooseneck because the 7.50 R16 tires on the trailer are about shot.

Do you think this would be a problem?

Thanks for your help!


Answer
David,

A 7.50R16LT Load Range E has a maximum load carrying capacity of 2755 # (single) and 2470 # (dual) at 80 psi, with a diameter of 31.8" and a section width of 8.7" on a 6" rim with an approved rim width range from 5 1/2 to 6 1/2".

An LT245/75R16 Load Range E has a maximum load carrying capacity of 3042 # (single) and 2778 # (dual) at 80 psi, with a diameter of 30.5" and a section width of 9.76" on a 7" rim with an approved rim width range from 6 1/2 to 8".

This means that you can do what you are considering if, and only if, the following are acceptable.  If even one of those is not acceptable, then you can't do this:

1) If the rim width on the trailer is at least 6 1/2".  This ought to be stamped somewhere on the rim - sometimes on the inside, which would require taking the rim off the trailer to see it.

2)  If there is more than 1" side clearance currently between the tire and the trailer:  1/2" because of the change in section width and the other 1/2" to allow for the tire flexing in cornering.

3)  If lowering the trailer 5/8" is acceptable.

4)  If the tires on the truck are not too old.  

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 code.

DOT codes are a 10 to 12 digit number located near the letters "DOT".  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 08.  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.