Radial vs Bias Trailer Tires and Can the Same Wheels Be Used for Both Types of Tires

Question:

I have an 18-ft Fleetwood CK18 travel trailer that came with ST205/75D14* Bias tires on 5-lug rims. Can I use the same rims for radial tires? I need to replace all my tires and some are recommending I go to radial. *Note: the trailer tag specifies ST205/75C14.

asked by: Al

Expert Reply:

The same wheels can be used for both bias and radial tires. You do not need different wheels for radial tires.

The tire you have now that is labeled ST205/75D14 is a bias tire because the D inside the tire size means diagonal or bias ply construction. A radial trailer tire will be labeled as ST205/75R14. The R inside the tire size meaning radial construction.

The trailer specification of ST205/75C14 is meaning you can use a bias or radial with a Load Range C rating. Normally on a tire the load range (B, C, D) will be labeled after the tire size, not inside the tire size.

I would strongly recommend using a radial tire like the Karrier ST205/75R14 Radial Trailer Tire, Load Range C, part # AM10234 over a bias tire. 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: Jeff D

Nathan

5/28/2020

Are D and R tires the same exact size? I’m being told I can’t switch a set of radial tires because they won’t fit under the fender.

Chris R.

6/1/2020

The overall size between a bias (D) and radial (R) ply tire is the same. I'm not sure who told you that but you can certainly go from bias to radial (or vice versa) without issue - assuming you're sticking with the same specific size.