What is the Difference Between a Letter D and R in Trailer Tire Size

Updated 12/09/2018 | Published 12/08/2018

Question:

Whats the difference between an R15 and a D15?

asked by: Jake

Expert Reply:

The letters R and D in a trailer tire size indicate what style of tire is used. If it's a D it's a bias-ply tire or if it's an R it's a 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. I attached a help article on trailer tire info for you to check out as well.

I attached a link to a page that has all of our 15 inch wheel tires as well.

expert reply by: Jameson C