Difference Between a ST175/80D13 and a ST175/80R13 Trailer Tire

Updated 11/19/2024 | Published 06/07/2014

Question:

I have a 1983 sunline camper st 175 80 d13 whats the dfference between that tire and the st 175 80 r 13

asked by: Steven S

Expert Reply:

The difference between the letter D in your ST175/80D13 and the R in the tire size of the Wheel and Tire ST175/80R13 part # AM31985 that you referenced is the tire construction.

D stands for bias-ply which is a less preferred tire construction, whereas R stands for radial.

Because of the construction of a radial tire, the tire has more flex and will allow for more ground contact. That will improve traction and better tread wear. It also gives the radial tire better stability.

The radial tire will normally run cooler, if not overloaded, which will help the tire last longer, especially when the tire is under a load.

I am including links to a couple of FAQ pages on trailer tires.

expert reply by: Jameson C

Wayne P.

8/24/2024

Thanks for your expert advice. I have a set of ST 175/80 D 13 tires, weight rating 1,360 lbs each on a old basstracker boat trailer from 1988. The tires are brand new. ????Question: what would be the speed rating on these tires? I can’t find a rating on either side of the tires. I just want to make sure they are safe at highway speeds.Thankyou, Wayne

Chris C.

11/16/2024

Interesting. I have 14s on a trailer that I just rebuilt. When I loaded the trailer with one ton of heating pellets the tires rub slightly on tbe fenders when cornering. I can't raise the fenders any more than they are without making the trailer look dorky. I am going to replace the 14s with 13s and think that D (or bias ply) tires will be fine. I use tbe trailer for trips to pick up building materials and an occasionally dump runs. Perhaps 500 miles per year. Very little highway driving. I think the tires will dry rot before I see the tread wearing so I can't see paying twice the price for radials. Do you disagree? Thank you. Chris.