Radial vs Bias 205/75-15 Tires on Horse Trailer

Question:

I just purchased four brand new ST 205 75D15 to replace all my tires that were ST 205 75R15. I would like to know which of the two is the better tire especially when I am pulling a horse trailer with two horses in it. I did the research and understand that there is a difference in the build of the tire and that the 75R15 runs cooler. I want to ensure that I am safe, especially since I am pulling precious cargo. Thank you and have a great day.

asked by: Dayle M

Expert Reply:

The "D" on your new ST205/75D15 tires stands for diagonal or bias ply construction, meaning that the tire's body plies crisscross. A radial tire's plies like what you previously had on your trailer branch out from an imaginary center of the wheel. As you mentioned in your question, a radial tire's construction will allow for it to run cooler than a bias ply tire. This is especially true when the tire is under a heavy load. The reason this is important is because excessive heat is the primary cause of tire failure.

A radial tire will also flex more than a bias tire, giving it better ground contact, traction and stability. One advantage that a bias tire has over a radial construction, which may be beneficial considering your application on a horse trailer, is that they will have a stiffer sidewall. This allows bias tires to be more useful for off road applications like farm use.

While radial tires are the better option when compared to bias ply alternatives, using the new bias tires on your horse trailer is certainly not unsafe. As with any trailer tire, you will just want to make sure you are always inflating them to their maximum psi as listed on the tire sidewall and staying under their load capacity and speed rating.

If you decide to go back to radial tires on your trailer, I recommend the Taskmaster Provider # TR20515D. These have a maximum load of 2,150 pounds at 65 psi and a speed rating of 81 mph. They also include a 2-year limited warranty.

I have also attached a couple of articles on trailer tires and wheels that you may find helpful.

expert reply by: Chris R