Bias Ply vs. Radial Tires. Understanding Which is Better for Your Trailer

Neighbors Trailer

Feb 16, 2023
2606
6 min read
trailer tires

If you have ever shopped for trailer tires, you have likely encountered two main construction types: bias ply and radial. Both will carry your load, but they behave differently in ways that affect safety, handling, tire wear, and cost. Choosing the wrong type for your application can lead to premature tire failure or compromise the safety of your tow rig. This guide breaks down the key differences between bias ply and radial trailer tires to help you make the right call.

Understanding How Trailer Tires Are Constructed

Tire construction refers to how the internal plies (reinforcing layers) are arranged inside the tire carcass.

Bias Ply Tires

Bias ply tires have their cord plies arranged at an angle (typically 30 to 40 degrees) to the direction of travel, crossing each other in a diagonal pattern. This creates a rigid, interlocked structure throughout the entire tire, including the sidewall and tread area. The sidewall and tread are effectively the same structure.

Radial Tires

Radial tires have cord plies that run perpendicular (at 90 degrees) to the direction of travel, from bead to bead. A separate belt package stabilizes the tread area. This separates the sidewall and tread functions, allowing each to flex independently. The tread belt is stiff for load-bearing while the sidewall flexes freely.

Bias Ply vs. Radial Tires: Head-to-Head Comparison

Category	Bias Ply	Radial
Tread wear	Faster, less even	Slower, more even
Heat buildup	Higher at speed	Lower, dissipates better
Ride quality	Stiffer, more vibration	Smoother, better stability
Sidewall strength	Very stiff, puncture resistant	Flexible, can bulge under overload
Load capacity	Excellent for static loads	Excellent for dynamic loads
Cost	Lower upfront	Higher upfront, longer lifespan
Best application	Low-speed, occasional use	Highway towing, frequent use

Tread Wear and Tire Longevity

Bar graph comparing average lifespan of bias ply tires at 3 years versus radial tires at 6 years

NeighborsTrailer.com

Radial tires typically last significantly longer than bias ply tires under comparable use conditions. The separate belt construction reduces heat buildup at highway speeds, which is the primary enemy of tire longevity. Bias ply tires generate more heat because the entire carcass flexes as a unit with every rotation. For trailers that regularly travel at highway speeds, this heat differential is a significant concern.

When Bias Ply Tires Make Sense

Despite the overall performance advantages of radials, bias ply tires remain the right choice in certain situations.

Low-speed, farm, or construction use: Trailers that rarely travel above 45 mph generate less heat, negating radial's thermal advantage. In these applications, bias ply's stiffer sidewall offers better puncture resistance on rough terrain or job sites.

Budget-sensitive applications: Bias ply tires cost significantly less upfront. If a trailer is used infrequently (a few times per year) and only at low speeds, the cost savings may outweigh the performance gap.

Older trailer designs: Some older trailer frames and suspension systems were designed around the stiffer handling characteristics of bias ply tires. Switching to radials on these trailers can sometimes alter handling behavior. When in doubt, follow the trailer manufacturer's recommendation.

When Radial Tires Are the Better Choice

For most modern trailer applications, radial tires offer clear advantages.

Highway and interstate towing: At speeds above 55 mph, radial tires run cooler and more stable. Heat buildup is the number one cause of trailer tire blowouts, so the thermal advantage of radials directly translates to safety.

Long-haul or commercial use: Trailers that log significant mileage will benefit from radial's longer tread life. The higher upfront cost is typically recovered through fewer replacement cycles.

Enclosed and cargo trailers: These trailers often carry high, concentrated loads and travel long distances. Radial construction handles these demands better. For guidance on maintaining these tires properly, see our guide to preventing dry rot in enclosed trailer tires.

Trailers used frequently: The more a trailer is used, the more the total cost of ownership calculation favors radials. Frequent use also means more time at highway speed, amplifying the heat and wear advantage.

Can You Mix Bias Ply and Radial Tires on a Trailer?

No. Mixing bias ply and radial tires on the same trailer is dangerous and should never be done. The two tire types have different flex characteristics, load distribution patterns, and cornering behaviors. Running them together creates uneven loading between axles, unpredictable handling, and increased risk of trailer sway. Always use matching tire construction across all axle positions.

Understanding ST Tire Markings

Trailer tires carry a size and construction marking on the sidewall. An ST205/75R15 tire breaks down as follows: ST = Special Trailer service, 205 = section width in millimeters, 75 = aspect ratio (sidewall height as a percent of width), R = Radial construction, 15 = wheel diameter in inches. Bias ply tires use a "D" or "B" in that position instead of "R." Always replace with a tire that matches the original size and construction type unless you are intentionally upgrading the full set.

When renting a trailer through Neighbors Trailer, every booking is automatically covered by NT Protect, mandatory coverage charged at a few dollars per day at the time of booking. While NT Protect provides financial protection, you should still inspect the tires before departure. Radial or bias ply, a visually compromised tire needs attention before the trip begins. For more detail on trailer tires, our guide to choosing the right tires for your trailer has a full breakdown of specs and ratings.

Frequently Asked Questions

Are radial tires always better than bias ply for trailers?

For highway use and frequent towing, yes. For low-speed, occasional-use applications, bias ply can be the better value. The right answer depends on how the trailer is used.

Do radial trailer tires cost more?

Yes, radial tires typically cost 20 to 40 percent more upfront than comparable bias ply tires. However, they often last twice as long, making the total cost of ownership similar or lower over time.

Can I put car radial tires on a trailer?

No. Passenger car radials (P designation) are not designed for the lateral forces and static load demands of trailer service. Always use ST-rated tires on trailers.

How do I know if my trailer has radial or bias ply tires?

Look at the size marking on the tire sidewall. An "R" in the size designation (like ST205/75R15) indicates a radial tire. A "D" or "B" indicates bias ply (like ST205/75D15).

Should I replace bias ply tires with radials?

You can upgrade from bias ply to radial as long as you replace all tires simultaneously and maintain the correct size, load range, and speed rating for your trailer. Never mix the two types.

Content updated March 2026