09/06/10

Tires and load range designations on tires have changed over the years. It used to be a 6-ply or 8-ply tire, and you knew the higher the number the stronger the tire.
Now they use a letter to designate load range and tire strength. To help simplify this you can take the letter for the load range on the tire, determine what number it represents in the alphabet, and multiply that by two, to determine the strength of the tire.

It sounds much more difficult than it is. If your tire is a load range "D" that is the 4th letter in the alphabet. 4 X 2 equals 8 so a load range "D" tire is equivalent to an 8-ply tire in strength.

This tip contributed by Mark Polk at RV Education 101