What is the Difference Between ST175/80D13 Tires and ST175/80R13 Trailer Tires

Expert Reply:

The D in 175/80D-13 indicates that it is a bias ply tire where as the R in 175/80r-13 indicates that it is a radial tire. The difference is how the steel belts inside are oriented. Bias ply tires are generally better in off road types of situations. Radial tires track better and run cooler. You do not want to mix the different construction types because that can lead to uneven wear and decreased ride quality.

Each type of tire will have a load range such as # AM10210 which is a radial with a load range D. The load range is an indication of the capacity. This tire is rated for 1,610 pounds at 65 psi as is the bias ply version, # AM1ST77. Going with a higher capacity tire than stock does not increase the trailer capacity.

I have included a link to all of the tires we carry in size 175/80-13. I have also included a link to our informational article on trailer tires for you.