My new 5000# GN has Goodyear tires... 15" trailer tires, load range D, but only SIX PLY and they're also RADIALS.  I knew this when I bought it and just figured I'd replace them.  The thing is, based on the markings on the tire they're FINE... loaded, the trailer is still only around 7000# and each tire is rated for something like 2150#.

SOOOOOOOOO, can anyone post a good educational website with info about TRAILER tire load ratings and ply choices?

Thanks!!

As Chad said, I would not worry about the ply, but more importantly what weight they are rated to carry.

Your load rating is a combination of the tires, wheels, axles, springs and what ever weight that sits on the hitch.

If your trailer is a GN and has 25% of its weight resting on the Gooseneck Hitch.

7000lbs  * 25% = 1750 lbs on hitch

7000lbs * 75%= 5250 lbs on tires.

4 tires at 2150 lbs each = 8600lbs total. So your loaded trailer at 5250# is well within the limits of the tires.

If it's a bumper pull with 600 lbs on the hitch leavng 6400# on the axles and you are still well under the max.

Your "D" rated tires are typically rated at 65psi.  A "E" tire will usually run at 80psi. A "G" rated tire runs at 110psi.

Buying a higher rated tire may let you hold higher pressure, But that doesn't mean your rims will hold the extra pressure. I definitely would NOT put a "G" rated tire as a replacement on a rim designed for "E" rated tires.  Somebody may just read the label on the tire and not look at the rim and put 110 psi and blow the rim to pieces.