Do Bias Ply Tires Have a Larger Diameter that Radial Tires in the Same Tire Size  

Question:

Expert Reply:

Bias ply tires can have a larger diameter than a radial tire of the same size. This is due to the way they are constructed. The cords in a bias ply tire run at a 32 degree angle to the direction of travel. This gives the tires a stiffer sidewall. The cords in a radial tire run at a 90 degree angle from the direction of travel allowing for more flex and better traction. The diameter difference is usually very minimal and unfortunately there is no set rule or dimension for the diameter differences.

There are a few things that can affect the overall diameter difference. The tire manufacturer will play a big role. Not all tire manufacturers make their tires to the same exact specs. A Kenda trailer tire and a Carlisle trailer tire could have slightly different dimensions in the same tire size. Also, the load range of the tire will also have an affect. A load range C tire will have a slightly smaller diameter than a load range D tire.

I am surprised to hear you want to switch to bias ply tires. Bias ply tires are typically better suited for trailers that see off-road conditions such as agricultural or construction trailers. Radial tires are best for highway or on-road use. They provide better traction, tread wear and they typically run cooler than a bias ply tire.

If you have some room to work with in your fender (a couple inches or more), then you should be okay to switch to a bias ply tire. If it is a tight fit for your radial tires, I recommend sticking with radial tires. The difference in diameter will usually be less than an inch.

expert reply by: John H

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