When it comes to keeping your trailer in optimal condition, the right tires are an absolute must. Whether you’re hauling equipment, vehicles, or cargo, choosing the best trailer tires can make a significant difference in safety, performance, and durability. In this article, we’ll explore some of the best trailer tires available for 2025, with a special focus on the ST 205/75R15 and 205/75/15 trailer tire sizes, as well as answer some of the most common questions about trailer tire selection.
What’s the Difference Between 205/75R15 and 205/75D15?
One of the most frequent questions we get from trailer owners is: “What’s the difference between 205/75R15 and 205/75D15?” These numbers refer to the tire size and construction type, and understanding them is essential for choosing the right tire for your trailer.
- 205/75R15: The “205” refers to the tire’s width in millimeters. The “75” is the aspect ratio, which means the tire’s sidewall height is 75% of its width. The “R” indicates that it is a radial tire, which is the most common type for trailer tires. Finally, “15” is the rim diameter in inches.
- 205/75D15: The “D” in this size indicates that the tire is a diagonal ply tire (also called bias-ply), which was the traditional construction method before radial tires became common. Diagonal ply tires are often more rigid and provide a smoother ride but at the cost of less durability compared to radial tires.
While both tire types may look similar in size, radial tires (R) are generally considered better for trailers due to their enhanced durability and better handling on highways.
If you’re in need of the best 205/75R15 trailer tires, you can check out our full selection at Namatireonline.
What Does “ST” Mean on a Trailer Tire?
Another common question is: “What does ST mean on a trailer tire?” The “ST” stands for Special Trailer, which is a designation used for tires that are designed specifically for trailers. Unlike passenger vehicle tires, ST tires are built to carry heavier loads, withstand the demands of constant trailer use, and provide better durability over long distances.
This makes them ideal for trailers that will be used for heavy-duty hauling or long-distance travel. If you are towing a boat, RV, or construction equipment, you will likely need to look for ST-rated tires such as the ST 205/75R15.
Which is Better, D or R Trailer Tires?
When choosing trailer tires, you’ll often come across the terms D (bias-ply) and R (radial). But which one is better?
- Radial Tires (R): Radial tires, such as the ST 205/75R15, are designed with steel belts running perpendicular to the direction of travel. This results in a flexible sidewall and better traction on the road. Radial tires are generally preferred for highway use due to their improved fuel efficiency, durability, and smoother ride.
- Bias Ply Tires (D): Bias-ply tires, on the other hand, have layers of rubber that are angled at 30-40 degrees to the direction of travel. This gives them a firmer, more rigid structure, which can be beneficial for trailers carrying heavy loads at slower speeds. However, they can wear out faster and don’t perform as well on highways as radial tires.
For most trailer owners, radial tires (like the ST 205/75R15) are the better option, especially if you plan on driving long distances on highways. However, bias-ply tires might be preferable for certain off-road applications or for trailers that carry very heavy loads at lower speeds.
What is the Tire Pressure for a 205/75R15 Trailer Tire?
Proper tire pressure is essential to ensure your trailer tires perform at their best and to avoid accidents caused by under or over-inflation. For the 205/75R15 trailer tire, the recommended tire pressure typically falls between 50-75 PSI, depending on the load you are carrying. Always check the manufacturer’s specifications on the sidewall of the tire or the trailer’s owner’s manual to ensure you’re inflating your tires to the correct pressure.
What is the Difference Between 75R and 75D Tires?
The difference between 75R and 75D tires is mainly in the construction.
- 75R refers to radial tires, where the internal layers of fabric and steel are aligned perpendicular to the direction of travel, making them more flexible and capable of providing a smoother ride with less rolling resistance.
- 75D refers to bias-ply tires, where the layers are arranged diagonally, resulting in a more rigid tire. These tend to be more durable under heavy loads but can create more road friction and wear out faster.
In most cases, 75R tires (radial) are recommended for trailers used on highways, as they offer better fuel efficiency and longevity compared to 75D tires.
Which Trailer Tire Lasts the Longest?
The longevity of trailer tires depends on several factors, including construction type, maintenance, and usage. Generally speaking, radial tires tend to last longer than bias-ply tires. Among the best trailer tires for longevity are those designed with a high ply rating, such as 10-ply tires, which offer greater load capacity and durability.
To ensure that your trailer tires last as long as possible, make sure to follow proper tire maintenance practices, including checking tire pressure regularly, rotating tires when necessary, and avoiding overloading your trailer.
For long-lasting ST 205/75R15 tires, consider choosing high-quality options from reputable brands like those available on Namatireonline.
How to Choose Trailer Tires?
Choosing the right trailer tires can be a daunting task, but keeping these factors in mind will help you make an informed decision:
- Tire Size: Make sure to select the correct tire size based on the specifications of your trailer. Common sizes like 205/75R15 or 225/75R15 are popular choices.
- Load Capacity: Consider the weight of the cargo you will be hauling. Trailer tires come with different load ratings, and it’s essential to match the tire’s capacity with your trailer’s weight.
- Construction Type: As discussed earlier, radial tires (R) are ideal for highway use, while bias-ply tires (D) may be better for off-road or heavy-load applications.
- Tire Pressure: Make sure to adhere to the recommended tire pressure for your specific tire type and load capacity.
If you’re unsure which trailer tires are best for you, check out our tire selection at Namatireonline, where we offer a wide variety of options like ST 205/75R15 trailer tires and more.
What Does D15 Mean on a Tire?
The “D15” label on a trailer tire refers to the rim diameter (15 inches) and the bias-ply construction (D). It’s important to select a tire that is compatible with your trailer’s rim size to ensure proper fit and performance.
Can You Mix R and D Tires?
Mixing radial (R) and bias-ply (D) tires on the same trailer is not recommended. This is because the performance characteristics of these tires are different. Radial tires are more flexible, while bias-ply tires are stiffer, which can lead to uneven wear and handling issues. It’s best to use either all radial tires or all bias-ply tires to maintain stability and ensure the safe operation of your trailer.
Conclusion
Choosing the best 205/75R15 trailer tires or other trailer tire sizes like ST 205/75R15 can significantly affect the safety, performance, and durability of your trailer. By understanding the differences between tire types, sizes, and construction methods, you’ll be better equipped to make an informed decision. Whether you’re hauling a load on the highway or tackling off-road terrain, there’s a tire out there that suits your needs perfectly.
For more information or to purchase your next set of trailer tires, visit us at Namatireonline. We offer high-quality tires for every trailer need, from 10-ply trailer tires to specialized RV tires and more. Stay safe and ensure your trailer is road-ready with the best tires available in 2025!
