Differences Between Radial and Bias Ply Trailer Tires

Updated 07/28/2014 | Published 07/26/2014

Products Featured in This Question

Karrier ST175/80R13 Radial Trailer Tire with 13" White Wheel - 5 on 4-1/2 - Load Range D

(1556)

$146.14

Question:

I have a tent trailer, the tires that are on now are ST175/R13 . What is the difference between R13 and D13, can I use a D13 as a spare tire. thx

asked by: Gordon S

Expert Reply:

The difference is that D stands for bias-ply and R stands for radial.

The main difference between a radial ply and a bias ply tire is how the tire is constructed. The cords inside a bias ply tire run at a 32 degree angle to the direction of travel, and the cords on a radial tire run at a 90 degree angle to the direction of travel, or across the tire from wheel lip to wheel lip.

A radial tire flexes more than a bias tire, giving it better ground contact, traction, stability, and tread wear.

A radial tire will normally run cooler than a bias ply tire, especially when the tire is under a load. A tire that runs cooler will last longer.

A bias ply tire has a stiffer sidewall than a radial, a feature that might be useful for off road applications like farm use.

At one time radials were more expensive than bias ply tires, but now they are closer in price. This makes radials a much better value.

To answer your question though yes, you could use a bias ply as a spare in an emergency situation to replace a radial. However, I would still recommend you use a radial just to keep everything consistent. For that I would recommend the # AM31985.

I attached an FAQ on trailer tires for you to check out as well.