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Serving the RV Community for 30 years

Exploring the country and enjoying special times together is often done in an RV Trailer. To fit the unique and diverse traveling preferences of people across the country, RV trailers come in a wide variety of sizes and configurations.

Tires are an important safety component of every RV trailer. These tires will wear out and will need to be replaced many times throughout the life of the trailer. Even though all RV trailers have tires, there are different types of tires that are used on RV trailers. These various types of tires have different characteristics. As RV trailer owners, it is important to understand more about these critically important components which work hard to transport us safely to our destination so that we may enjoy the beauty and wonder of creation and share good times with friends and family. Let’s take a little walk through the types of tires that may be found on RV trailers.

Tire Construction

RV Trailers are used to carry the extra stuff needed to comfortably enjoy the types of exploration and recreation activities in which we choose to participate. Each piece of this stuff has weight, and that combined weight is carried on various structural components of the RV. A large portion of that weight is carried by the trailer tires. This leads us to the most important aspect of an RV trailer tire – load carrying capacity.

RV trailers can weigh as little as a few hundred pounds up to almost 30,000 pounds, or 15 tons. That is a bunch of stuff that tires must be able to carry. Tire selection for an RV trailer is done by making sure that the needed load or weight can be properly carried by the trailer tires. The National Highway Transportation & Safety Administration (NHTSA) has developed vehicle safety standards that specify the proper load carrying capacity of tires for newly purchased vehicles. The Recreation Vehicle Industry Association (RVIA) has gone even further to enhance many of these foundational standards for RV Trailer tires. At the heart of these standards is tire load carrying capacity, which is the most important specification to match a tire to an RV trailer.

Almost all RV tires are radial tires. The term radial refers to the internal construction of the casing or carcass of the tire, which is the doughnut portion of the tire and is defined by the tire’s sidewalls. The primary function of the casing or sidewall is to provide the structure to carry the load or weight. The sidewall also provides some protection from road hazards.

The other major part of the tire is the tread package, which is the outer layer of the tire that contacts the road. The tread package is the vehicles’ contact point with the road and provides maneuverability and stability of the vehicle on different surfaces and conditions.

Trailer Tire Types Defined

It is important to understand that there is not a specific type of tire that is made solely for an RV trailer. RV trailers are only a portion of the types of small or medium trailers that are built. Cargo trailers, boat trailers, flatbed trailers, livestock trailers, et cetera make up most trailers that are towed across the country every day. Even though it is possible to use different types of tires on an RV trailer, some tires are much better suited for the job. The four most common radial tire types that might be found on an RV trailer are passenger car tires, light truck tires, special trailer tires, and commercial truck/bus tires. Each of these tire types have some unique characteristics that may make them better suited for a certain application and for RV use.

Passenger Car Tires (P-metric)

Passenger car tires are designed for relatively small vehicles with the primary purpose of moving people from one location to another. They are probably the most prevalent type of tire that is produced and purchased in America. The primary cargo for a passenger car tire is people, so ride comfort is an important aspect of the design of this tire type. The load that passenger cars carry is usually focused on the weight of the number of potential passengers and a small amount of personal cargo, like luggage or personal items. So, the loads are relatively small and the additional design characteristics focus on ride comfort, steering, and drive handling for a motorized vehicle. Passenger car tires are tested for very high speeds. This is called the speed rating of the tire, which for passenger car tires, is usually well over 100 mph. Passenger car tires are rarely used on RV trailers, but they have been used on some smaller RV trailers. As required by Federal Safety Standards, there must be additional load reserves calculated when passenger car tires are used on trailers. This extra load requirement as well as the design purpose often eliminates the use of passenger car tires for RVs because of the smaller load capacities for the range of tire sizes that are available. RVIA has also set a higher capacity standard for tires used on small and medium trailers, which means the use of passenger car tires on new RVs is rarely done any longer. Passenger car tires, however, may also be found on small pickups, small sport utility vehicles, and minivans, which function to move small groups of people around, and are used to tow smaller RVs.

Light Truck Tires (LT Tires)

Light truck tires are mostly found on slightly larger motorized vehicles. This type of tire must be able to function on a motorized vehicle that steers and has a drive axle. Larger pickup trucks, sport utility vehicles, passenger vans, cargo vans, small delivery trucks, and smaller motor homes are typical vehicles that use light truck tires. The function of these vehicles is less about moving people around and more about moving cargo items from one location to another. These tires are designed to carry more load than passenger car tires. When a tire is designed to carry more load, comfort is given less priority. To carry more load, the internal structure of the tire must be supported with stronger material which means that some degree of comfort is sacrificed. Often the word stiffer is used to describe the needed increase of internal structure for the casing to carry more weight or load. Stronger is probably a more appropriate word to describe the needed difference between a passenger car tire and a Light Truck tire since the purpose of the vehicle is more directed to carrying more cargo and less focused on the comfort of the passengers.

Light Truck tires also have a variety of tread designs to deal with unique surface conditions. Since these tires are used on larger load-carrying vehicles, the tires may be used on different surfaces that are not hard typical road surfaces like asphalt. Dirt, gravel, sand, mud, and snow are road surfaces that are often encountered with these larger load hauling vehicles. Therefore, LT tires are fitted with differing tread packages designed to provide better contact and maneuverability on a variety of surfaces. Because these tires are primarily used on motorized vehicles, the speed rating is often well over 100 mph for LT tires. While there are a limited number of off-road small RV trailers, most RV trailers are towed on typical hard road surfaces. The tread package that works well for a trailer is a simple design that should help the vehicle follow straight behind the tow vehicle on hard surfaced roads. This type of tread is found on some LT tires; therefore, some LT tires can be a good fit for some RV trailers. There are even a few LT tires that have been marketed by the tire manufacturer as good trailer tires.

Special Trailer Tires (ST Tires)

ST or Special Trailer tire have been designed specifically for use with all types of trailers. Because of their design characteristics, ST tires are most often the type of tire that is fitted on most small to medium-large sized RV trailers. There are two primary design differences that make ST tires well suited for trailers. Because trailers are designed to carry cargo and that cargo is often heavy, ST tires have even more load capacity than a similar sized LT tire. Comfort is not really a concern because trailers are not intended to have people as cargo. The tread package or pattern on an ST tire is designed to follow in a straight line behind the tow vehicle. Because of these specific tread designs, ST tires cannot be used on a motorized vehicle. They are not designed for steering maneuverability or drive axle applications. A limiting factor for ST tires is the speed rating. Just a few years ago, almost all ST tires were limited to a speed rating of 65 mph. Because of some international trade changes most ST tires now have higher speed ratings, but they are still not as high as passenger or LT tires. Most ST tires now have speed ratings that range from 75 mph to over 90 mph with some still rated at 65 mph. Just because the published speed rating is higher does not mean that it is a good idea to travel at these higher speeds. Speed is an important factor in trailer sway which is a significant driving safety concern. Remember also that ST tires are used on all types of trailers not just RVs, which often have greater value than flatbed, cargo, or utility trailers.

Commercial Truck/Bus Tire

Commercial Truck and Bus tires are designed to carry very heavy loads and are designed for rugged service. The size of RV trailers is increasing all the time; some custom RV trailers are weight rated to over 15 tons or 30,000 pounds. With these heavier trailers the only tire that can be used is a commercial tire. There are some commercial tires that are sized and well fitted to use on these larger RV trailers. The commercial tires will carry even more load than an ST tire. Many have tread designs that work well for trailers, and some are even specifically made for trailer use only, like a ST tire tread design. Speed ratings usually range from 62-85 mph like an ST tire. Many of the Commercial trailer tires can be identified by the rim diameter on which they are mounted. Except for some smaller European 16” commercial tires, the rims are in ½ inch sizes – 17.5, 19.5 and some large custom RV Trailers even use 22.5 tires.

Replacement Tires

As RV owners, we are usually not aware of the weight of our stuff and when we are confronted with the idea, our mind usually scans for large items. However, we need to remember that every single item has weight and the accumulation of the weight of each item sneaks up on us. We at RVSEF weigh RVs and have observed that year after year, owners struggle with overloading their RVs. Even though many RVs provide a large amount of space to store our stuff, it does not mean that we can just fill that space with whatever we want. Weight, not volume, is the important consideration for the components of the vehicle to safely carry people and our stuff as we travel. Consistently, 50-60% of the RVs that are weighed exceed a vehicle weight rating. Often the consequence of overloading results in tire failure or reduced tire life. This can be costly in various ways, but most importantly it can be an increased risk to the lives of everyone who travels down the road.

Tires are consumable which means that they wear out and will have to be replaced regularly. Because of the unique nature of recreation vehicles, there are many tire questions that arise when it comes to replacing tires. One of the more often suggested replacement options is to replace the ST tires with LT tires. This concern often arises because of the quality concern of some ST tires. As we discussed earlier, it is very important to understand the differences between ST and LT tires. The primary difference is that the ST tire has a higher load capacity than a similar size LT tire. Here are examples of three types of tires with the same external dimensions and the load capacity for each tire type.

  • Passenger Car Tire – P225/75R15 can carry 1874 lbs.
  • Light Truck Tire – LT225/75R15D can carry 2205 lbs.
  • Special Trailer Tire – ST225/75R15D can carry 2540 lbs.

If we placed these tires next to one another they would appear to be pretty much the same size. The treads would be a little different, but the width, height, and hole in the middle are almost identical, so, they could all fit on the same rim and probably in the same wheel well. However, we can see that there is a significant difference in the load carrying capabilities of the tires. When we lift them up, we would be able to tell a difference. Higher capacity tires weigh more, because it takes heavier duty material embedded in the rubber to strengthen the casing or sidewalls, so that the tire can carry more weight or load.

So, when an ST tire is replaced with an LT tire, that LT tire may immediately be overloaded because the LT tire cannot carry the same weight as the ST tire. Great care must be taken to know the weight of the RV so that tires with insufficient capacity are not purchased as replacement tires. Overloading is a very common issue with RV tires. Often people have purchased LT tires as replacement tires and then weighed the RV only to find out that the new LT tires are now overloaded because they do not have the needed capacity to carry the weight of the loaded RV. This does not mean that LT tires cannot be used as a replacement for an ST tire. It simply means that you need to be careful and know the actual weight on the tire and make sure the replacement tire has enough capacity to properly carry that weight. If the LT tire does have the load capacity to carry the known weight, then it can be a great replacement tire. However, if the LT tire does not have the load capacity to carry the weight, then it is not a good fitment and should not be used. If the LT tire is overloaded its lifespan will be prematurely shortened. Some folks get away with this change without knowing the weight measurements on each axle end, but that is a dangerous game of probability to play with the lives of family members and the lives of others traveling down the road next to the trailer.

It's A Hard Life

RV Trailer tires have a challenging life. They are usually on axles that are placed close to one another and function as a group. This proximity is needed but also creates additional lateral stress when turning or backing. This additional stress occurs to the sidewalls and where the tread package is attached to the casing of the tire. One simple way to reduce the stress on the tires when backing is to watch the tires. When you see the tires contorting, pull forward about a foot or two and this will relieve some of the pressure on the tires. Sitting for extended periods of time is also hard on the compounds that make up the tire. The best way to handle this is to travel more to see more of the country and spend more time enjoying family and friends.

These stresses are a normal part of the life of a trailer tire, but they also contribute to a shorter life span as well. Trailer tires often need to be replaced sooner than motorized tires even though the tires have traveled fewer miles. Understanding these conditions and the weight carrying capacity of RV tires is important for an RV trailer owner to consider, so that wise decisions, proper maintenance, and safe operation can provide years of enjoyment and pleasure in this wonderfully unique vehicle.

RV Trailer tires are an often-discussed topic among RV Trailer owners with many misunderstandings and assumptions. Knowing the different types of tires and how they are used on RV Trailers is a good first step to dispelling these often-repeated misunderstandings. While these different types of tires have all been used on RV Trailers, some types fit this application better than others. RV Trailers are boxes designed to carry heavier loads; therefore, the load capacity specification is extremely important to know and keep in mind when purchasing replacement tires. Passenger car tires are rarely a good option, except for possibly very small light weight trailers. LT or light truck tires carry a more load and are usually good quality, but diligent care must be taken to make sure there is enough load capacity for their specific use. With newer standards for additional reserve capacity, LT tires are less often fitted on new RV Trailers. ST or Special trailer tires are the most common type of tire used on small, medium, and medium-large RV trailers. Commercial tires are the most rugged type of tire and have the greatest load capacity. They are commonly seen on larger fifth wheels and some large custom conventional trailers.

RV Trailer tires have a hard and stressful life, which means they age a little more quickly than motorized tires. Caring for the tires and regularly checking their condition is a good habit to add to your toolbox of RV skills and practices. Careful observation and knowing how to manage these important safety components will help to enjoy RVing and experience life’s beauty and shared good times with friends and family.