Not all tires are equal! When talking about car tires and trailer tires, each type has its special applications, where they can safely perform.
Let's compare tires to see how they perform and what they have to offer.
Design Differences Between Vehicle and Trailer Tires
If you wish to compare tires, you will clearly see the difference between car tires and trailer tires. From their tread pattern to their sidewall structure, these tires are distinct to ensure their safe performance in their intended use.
Load capacity, traction, handling, and even durability at high speeds are significantly different between passenger tires compared to trailer models. But, why is this so?
The main thing we need to consider is driving stress and how these tires handle it.
Passenger car tires are the only link between the road surface and the vehicle. Therefore, they are responsible for the vehicle's performance, handling, and traction, as they transfer power when accelerating or braking. Sharp turns don't cause issues either. Longer tread life is guaranteed, even though they are often used daily.
On the other hand, the main purpose of trailer tires is their load capacity and towing capability. This is ensured with their stiffer sidewalls, that withstand loads and prevent trailer swaying. Trailer tire construction is optimized to safely handle the stress created by towing, placing emphasis on following the tow vehicle.
Therefore, the main difference between trailer tires and passenger tires is the pressures they face. And yet this small distinction changes everything!
The Structure and Tread Design of Standard Tires
Passenger car and light truck tires, or as they are known P-metric and LT tires, are usually manufactured with a radial ply structure. Depending on the car tire type, their internal structure and tread design can greatly vary.
Yet, a standard passenger vehicle's tires are required to withstand the following pressure:
- The pressure of acceleration, where tires must provide traction and ensure stresses
- The friction of braking, where tires have to stop the vehicle and withstand pressure
- Turning and maneuvering pressure, where the tread pattern and structure deform to provide better traction
Passenger tires compare to LT tires as their intended use is similar. They have to provide traction and controllability, even if their vehicle's main application serves different needs. Weather conditions, load durability, tread life, and tread wear, as well as other performing aspects, need to be considered when choosing the correct car tire set.
Trailer Tires are Built Different
Trailer tires are manufactured with thicker sidewalls and stable footprints than car tires. This is due to their primary purpose being load hauling and towing.
However, these thicker sidewall materials maintain the tire's optimal shape under heavy loads, without compromising its performance. As trailer models do not deal with the forces of acceleration, cornering, and braking, all of their focus can be turned towards stability and load capacity.
ST tire models can be manufactured with two distinct internal ply structures. They are available for purchase as bias and radial ply tires.
Let's see how these tires compare below, in our radial vs bias ply trailer tires section.
Bias Ply Trailer Tires
Bias-ply models are the thicker tires for trailers. This is due to the angled ply placement of the tire's construction, which provides better load durability and damage resistance.
When you see the bias-ply rating on tires, it means that they are sturdier. These tires are perfect for larger loads, which is why many heavy duty trailer tires feature bias-ply placements. Additionally, the bias construction stabilizes the tire, effectively resisting swaying throughout the towing process.
Yet, this construction type can be found in many different trailer tire models: from small trailer tires to E-rated trailer tires. All in all, there is a good reason why bias-ply tires are not a thing of the past.
Radial Trailer Tires
If smooth towing and better heat-resistance are more important, go with a radial trailer tire set. These tires feature belts placed at 90-degree angles, which optimize their pressure and stress durability.
As a result, these tires keep cool during their performance, preventing heat build-up. By eliminating this issue, radial trailer tires are able to offer better fuel efficiency, longer tread life, and smoother performance.
Radial trailer tire structure is similar to that of a standard tire, yet, they are still different. These trailer tires feature the thicker sidewalls needed for heavy load capacity. Therefore, radial models are also good trailer tires, just for different applications.
The part of the tire that is under just the tread of a radial tire is called the steel belt structure, which sits on the radial plies. These further enhance the tire's durability and performance.
Trailer Tires vs Car Tires Specifications
As mentioned before, standard tires and heavy-load tires are different... which means that passenger car and trailer models are also of versatile categories.
Therefore, car-trailer tires will have distinct markings, tire ply ratings, speed ratings, and load ranges, which determine their applications. Compare tires to each other, and their performance capabilities will be significant.
But, what exactly is the difference between E-rated tires for towing and regular tires for passenger cars?
Let us guide you through the various markings you will find on such tires.
Differences in Tire Markings
When it comes to passenger car, light truck, and trailer tire sizes, all of them differ - just to make our lives harder. However, the complicated system is in reality not hard to navigate if you know what you are looking for.
So, let's dig in:
Passenger car tires consist of three sets of numbers and two letters, not in that order. Let's take P255/55R18 as an example. In this tire size, P stands for P-metric, indicating passenger cars. The first number (255) is the width of the footprint, while the second one (55) is the aspect ratio or the height of the sidewall. R shows the radial car tire construction. Lastly, you will see the rim diameter (18 in this case).
Light truck tires are similar, but not completely the same. For context, let's take the same LT255/55R18 tire size. However, here the first two letters are already different, as they indicate that the tire is for light trucks. Then comes the tire width, aspect ratio, radial construction, and rim diameter.
However, bias-ply light truck tires also exist. For these instead of R, you will see just a dash (-). Additionally, LT tire size can also be shown in inches. For example, 33x11.5R18. Here, the tire has a 33-inch diameter, with an 11-inch width and an 18-inch rim diameter. It also has radial construction.
A trailer tire can feature a similar size. Only, the first letters will be ST, representing its Special Trailer application. After this, you will have the three sets of numbers for the width, sidewall height, and rim diameter. Radial tires will have an R before the rim measurement, while bias-ply models a dash (-).
Standard vs Trailer Tire Speed Ratings
When it comes to the speed rating of trailer tires vs car tires, heat-resistance plays a huge role. Car tires are designed to withstand driving pressure, even at higher speeds, while trailer tires focus on load.
Therefore, standard tires are able to keep cool at higher speeds. This means that car tires are also manufactured with higher speed ratings compared to trailer tire models. It all comes down to their heat resistance, as pressure builds up along the tread area during high speed applications.
But, what are the trailer tire ratings for speed?
It is recommended that trailer models, including even mobile home tires and camper tires, should not be driven at high speeds. Most trailer tires are manufactured with L speed ratings, which is equivalent to about 75 mph. While some models feature an M speed rating (81 mph), even these are leagues behind passenger tire models.
Compared to the most popular trailer tire speed ratings, passenger tire speeds are much higher. Even the slowest touring tire has a Q rating, which is equal to 99 mph. Yet, that is not the norm. Usually, passenger car and SUV tires, even some light truck tires, feature T (118 mph), H (130 mph), or V (149 mph) speed ratings. Additionally, high performance models can go at speeds of 168 mph, as they are marked with W speed ratings.
Passenger vs Trailer Tire Load Ranges
What's the difference between a passenger car tire and a trailer tire's load durability?
Well, tires for trailers were specially manufactured for heavy-duty applications, while passenger car models just need to handle regular, everyday loads. This is observable in their load ratings.
The trailer tire load rating is optimized as the main purpose of these tires is their durable load capacity. Additionally, like light truck models, these tires can also have single or double applications. Therefore, their load index will have two numbers on it. For example, 129/125. This means that is two tires are on the axle, each tire can handle 4079 lbs, however, if there are four tires that number drops to 3638 lbs/tire.
We need to keep in mind that smaller trailer tire models will have lower load ratings as well.
On the other hand, SUV and passenger car tires have smaller load ratings. Typically a passenger car tire will feature a load index below 100, while SUV tires range between approximately 100-115. This means that their load capacity ranges roughly between 1000-2600 lbs per tire.
However, it is also important to mention the trailer tire load range, as well. These depend on the ply rating of their internal structure, and passenger car/SUV tires do not have these. LT and trailer tire load range levels are similar, as it depends on the play rating. Therefore, load range E trailer tires are similar tire light truck tires of the same rating.
Load ratings depend on the ply rating, and they will regulate the maximum load pressure needed to handle larger loads.
Should You Use Standard Tires on Your Trailer?
The short answer is no! No, you should not use standard, LT tires on trailers.
Having light truck tires on trailer applications is not a good idea, as trailer tire structure greatly differs from LT or SUV designs. But, let's take a closer look at this:
What Makes Trailer Tires a Better Option than PT or LT Tires?
It should go without mentioning, that LT and trailer tires greatly differ, especially in their construction. Trailer tire models feature thicker sidewalls, which are manufactured to handle larger loads. Additionally, they also effectively stabilize the tire in order to minimize the possibility of the trailer swaying.
Compare tires to LT models and you will see similar load ranges. While light truck tires might be able to handle loads as well as heavy-duty trailer tires, their internal structure does not provide the stability necessary. These tires are designed for the frame and load distribution or light trucks, therefore, it is most likely that they will fail in trailer applications.
Irregular Wear Formations, Swaying, and Structural Damage
There are three main issues we need to talk about when it comes to mounting car tires on trailers. These are uneven and accelerated wear, trailer swaying, and tire failure.
When you mount standard tires on a trailer, the weight and pressure distribution will be irregular. This is because car tires are designed for different frames than trailer tires and will not be able to handle pressure accumulation. As a result, their footprint will start wearing prematurely and in an irregular pattern. However, the shortened service life is the least of your worries.
The bigger issue comes when looking at how these tires compare to trailer models' stability. Car tires are unable to provide the driving stability necessary to combat trailer swaying. In better situations, the trailer will be harder to handle, but it can easily tip over into its side if you are not careful.
Lastly, the internal structure of car or LT tires will not be able to handle the stress a trailer placed on them. This will quickly lead to structural failure. Unseen internal damage can easily cause accidents with a tire blowout, which will put both you and the vehicle in danger.
What about Using Trailer Tires on a Passenger Car or SUV?
If you value your safety, do not do it!
Even if you are thinking of using a trailer tire as a spare for your car, don't. Trailer tire structure is unable to handle the stress the car places on them. Not only do they not provide the traction necessary for vehicle applications, but their internal structure will also fail because of driving pressure.
Bad weather conditions, high speed highway driving, and sharp maneuvering will cause trailer tire failure. This can easily lead to even fatal accidents.
What does ST on Tires Mean?
ST on the tire's sidewall stands for "Special Trailer" indicating that these tires are designed specifically for trailers. Trailer tires feature a distinct construction from car tires or light truck tires, therefor they are only for trailer use. They optimize the trailer's performance, stability, and handling.
How Long do Trailer Tires Last?
How long trailer tires last will greatly depend on how often they are used yearly. For tires used for less than 5,000 miles a year, the aging process will get to them after about 6 years. On the other hand, trailer tires that are used more frequently will wear down in about 3-5 years.
What is the Minimum Tread Thickness for Passenger Car Tires?
The minimum tread thickness for passenger car tires is: 2/32". This is where the treadwear bars are placed. Once the tread reaches this point, they are no longer considered to be safe to be used. Most states require tires with 2/32" of tread depth to be changed for new tires.
Can You Put Trailer Tires on a Car?
No, you cannot use trailer tires on a car. The difference between car tires and trailer tires is too great for them to be interchangeable. In such applications, trailer tire construction of trailer models will not withstand the heat placed on them, which will lead to blowouts.