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Your Dad always bought bias tires for the trailer, but you think radials might be better. What is the difference between bias vs. radial trailer tires?

You don’t want to start a world war by going against your father’s thinking, especially when he’s trying to be helpful, but you’re not convinced that bias-ply tires are suitable for the trailer. The tires will have to handle a heavy load, but radials dissipate heat better than bias-ply. Your father advocates for the bias because he says they are safer. And to add more stress to the decision, the wife and kids are waiting for a decision because they are ready for vacation.

Bias-ply tires are stiffer, with thicker sidewalls than the typical radial tire, making them suitable for heavy equipment or agricultural machinery. At the same time, radial tires are more expensive, last longer, and are a better fit for highway trailer use.

But is it that simple? Could there be something to what your father is saying because he knows how heavy you load the camper trailer? And if the trailer he handed down to you all has used bias-plys all his life, was that because he just wanted to save money, or is it just a fundamental mistrust of the radial design? You don’t want to buy the wrong tire for the trailer and lose any time on vacation by towing the trailer to a garage. And what about trailer-sway? Which tire provides the best grip on the road?

Considering all the advances in technology and tire design, figuring out which kind of tire is best for your trailer can be a complicated task. Let’s see if we can’t seek the answers to some of your trailer tire questions and see what some experts recommend. Hopefully, we can save you from some headaches while pulling your trailer for a family vacation.

Table of Contents

What is the Difference in the Construction of Bias vs. Radial Tires?

There is a difference between bias and radial tires, and it has to do with the design and construction of the tire. In the early days of tire manufacturing, tire makers were having trouble making their product strong enough to last anytime, so they decided to add steel belts or nylon plys under the tread to reinforce the tire's stability. Some tire makers crisscrossed the belts at 30-45 degree angles (bias tires), but manufacturers of radials felt a 90-degree angle (basically straight across the face of the tire from side to side) was best.

Bias Ply Tires

Bias Ply, sometimes called cross-ply, uses rubber or nylon belts (plys) set at 30-45 degree angles to the tire face. The belts criss-cross in layers, forming an X pattern that reinforces the tire's rigidity and makes it resistant to puncture.

The advantage to this kind of tire construction is that the bias is a stiffer rolling tire with stronger sidewalls and the ability to handle heavier loads over short distances. This ability gives the bias better traction in a straight line, making it ideal for the trailer to haul something heavy but not too far. The bias-ply tire is perfect for handling the rough off-road conditions that construction equipment, logging trailers, or agricultural haulers endure. Many ranchers who travel down rough gravel or rocky mountain roads will opt for bias-ply tires because they know that their trailers will take a great deal of abuse from the jagged edges of surfaces of those kinds of roads. (You will find bias-ply tires on boat trailers that need straight-line traction when pulling a boat from the water).

Radial Tires

Radial tires lay the inner belts at 90-degree angles, producing a tire with more flexibility to the road surface. A radial tire wears better, which means it lasts longer. In addition, a radial tire has better traction, more stability, and dissipates the heat of the road surface more uniformly than a bias tire. Since heat can be a prime enemy of a tire’s health, the longer a tire is in motion, the more heat it will generate while pulling along the pavement's surface. Bias tires do not handle heat well, making them worse for asphalt or highway use.

What are the Primary Factors I Should Consider?

There are some primary applications to consider when choosing the right tire for your trailer.

Primary Purpose of the Trailer

If the trailer is for use on a ranch, as an essential utility hauler, where it will be out in the middle of the fields but rarely on the road, then bias might be right. If your trailer will be attached to the back of the combine and sit under heavy grain or corn weight, bias-ply should fit the deal. However, if you are taking the family travel trailer on a tour of the great 48 states and planning on burning up the miles, radials would be a better choice.

Miles Per Day

Bias-ply tires are better suited to trailers that are not traveling long distances, so if your trailer hauls a load of hay from the barn to the field and that’s about all, bias tires are the way to go. However, if you are pulling a bass boat because you are one of the best bass fishermen on the Bassmaster circuit, choose a good quality radial.

Weight of the Load

If the consistent load demands of the trailer are high, the bias-ply tire might be the best. A radial tire is usually practical for personal camper applications. (Just a note: uninflated tires do not handle load capacities like inflated ones. Be sure to keep your trailer tires inflated with the correct pressure for optimum performance).

Speed of Travel

Most trailer tires have a speed rating of 65 mph, and traveling above that speed will increase the friction and heat of your new tires. Read your trailer's specifications to ensure your tires align with your trailer's load and speed limits. (Remember to allow additional travel time as pulling a trailer means your tow vehicle carries an additional load. The slower you travel, the less strain you place on the vital components of the engine and transmission.)

What’s the Difference in Cost Between Bias and Radials?

Being equal (tire size), bias-ply tires are usually less expensive than radials, although the price differences between bias and radial tires are shrinking as manufacturing techniques improve.

Can I Mix a Radial and a Bias Tire on the Same Trailer?

No. The tires should not mix on the same trailer. The tires ride differently and have different functions. It is never good to use both bias-ply and radial tires on the same trailer.

How Can I Tell if I Have Bias or Radial Tires on My Trailer?

Every tire has a marking on the side indicating the tire size. Looking at the series of letters and numbers, you may notice something like 75/R15 - the letter R means it is a radial tire. Bias Ply tires will have the letter D where the tire size is.

How Can I Tell if my Present Trailer Tires Have Dry Rot?

If your trailer has been sitting a while (more than a few months), your tires may have deteriorated to the point of dry rot. Excessive marking or cracking in the tire's tread, bulging, or flat spots are specific indications of fatigue and should prompt replacement at once. However, a visual inspection of a tire may not reveal the actual state of the rubber. It is best to assume that a trailer sitting in the elements for any prolonged length of time will have faulty tires. Owners are better off replacing them than asking a tire to perform a task it can no longer handle.

Trailer tires should be checked often and replaced every five years, or 12k miles, if not more frequently.

Bias Vs Radial Trailer Tires

About The Author

Charles Redding

Charles Redding

I've spent many years selling cars, working with auto detailers, mechanics, dealership service teams, quoting and researching car insurance, modding my own cars, and much more.

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