ST vs. LT Tires: What’s the Difference?

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ST vs. LT Tires: What's the Difference?

Are you looking for a little entertainment? Head over to your favorite RV forum and search for “ST vs. LT tires,” and don’t forget the popcorn. The debate on which one is better for travel trailers and fifth wheels has raged on for years. It probably isn’t going to be settled anytime soon, either. If you are new to RVing, going through the forum discussions will present you with good information and wrong information. It can be challenging to figure out which is which. Hopefully, by the end of this article, you will understand how these two types of tires differ, so you can decide what is right for you.

What are LT Tires?

Cars will have P-type or passenger tires designed to give the buttery-smooth ride felt in most cars. If you want to carry a heavy load, P tires will bend and flex more than they should. Just like a wire gets hot when you bend it back and forth, a tire does too. Heat is the arch-nemesis of tires and causes many blowouts.

LT stands for light truck tires, and they are designed for heavier duty trucks and SUVs that need to carry more weight. They have thicker sidewalls and heavier duty construction than P-type tires. The thicker sidewall and materials used in the tire make it more rigid and harder to bend and flex as much as passenger tires.

Though they give a stiffer ride, they are still designed with the passengers’ comfort in mind. Manufacturers attempt to develop these tires to hold up and dissipate heat under a load while still flexing and rolling enough to provide a ride that is as comfortable as possible. Their tread is designed to have maximum traction under various road conditions and grip the road under a powered axel.

Though LT tires were not explicitly engineered for trailers, some travel trailers and fifth wheels come with this type of tire installed off the lot. That doesn’t mean LT tires are the best option for every camper out there. There are pros and cons to everything in life.

What are ST Tires?

Travel trailers and fifth wheels do not need to feel nice to passengers while traveling down the road since no one should be in them at that time. They don’t need the traction to grip and propel you forward because their job is to be pulled behind a vehicle. ST stands for “special trailer,” and they are engineered to hold up lots of weight. Their rigid walls prevent trailer sway. The tread design provides low resistance for ease of towing and better gas mileage.

They don’t just look different externally. Tim Fry, a senior development engineer with Goodyear Tire & Rubber Company stated, “The major difference is reflected in the polyester cords used in ST tires. These cords are bigger than they would be for a comparable P or LT tire. Typically, the steel wire also has a larger diameter or greater tensile strength to meet the additional load requirements. Because of the heavier construction for an equal volume of air space, an ST tire is designated to carry more load than a P or LT tire.”

On top of the internal differences, the rubber used in ST tires typically has more chemicals that resist aging and UV rays. The rubber compound itself is usually harder, giving it more sidewall strength. In short, ST tires are designed to be put on a trailer.

Trailer Tire Safety

A lot is riding in your RV tires, literally. It’s vital to follow tire safety when towing a travel trailer or a fifth wheel. Most tire blowouts are a result of either old tires that come apart or heat buildup.

Heat Buildup

Proper Inflation: Proper inflation is listed in two places. There will be a sticker located somewhere around your RV door, which has the GVWR, tire size, and inflation pressure. The tire itself will list the cold inflation pressure on them. Underinflated tires will bend and flex the tire more as the wheel travels down the road. This causes heat to build up, and remember, heat is the arch-nemesis of tires.

Overloaded Trailer: Overloaded tires cause flexing and add dangerous stress to your tires, resulting in blowouts. Your travel trailer or fifth wheel is not intended to have more weight than the GVWR states on that sticker mentioned above. GVWR stands for Gross Vehicle Weight Rating, and it is a measurement of all the things in the RV plus the weight of the RV itself. On top of the GVWR, each tire has a maximum load rating as well. Goodyear has a handy index and instructions on how to find your tires’ load index here.

Tire Blowout

There are two ways to find out if you are overloaded. Go to a truck stop with a CAT scale without your RV and weigh your towing vehicle, then go over the same scale with your RV attached. Subtract your vehicle’s weight from the second weight, and you have the total weight of your RV.

The best and second method requires you to find a place that specifically weighs RVs like RVSEF or Escapees RV Club Smart Weigh Program. They can weigh each tire separately and tell you if any tire is overcapacity.

Speed: If your RV is equipped with ST tires, they are not meant to be driven over 65 mph. You see and hear of people towing their trailers down the road at 80+ mph all the time. You also hear of ST tires blowing out all the time. Coincidence? There are some ST tires on the market, such as the Goodyear Endurance, which has an N speed rating allowing for a max speed of 87 mph. You can find the speed rating after the load rating on a tire. If your ST tire has no letter, then the speed rating is 65 mph.

Tire Source & Speed Rating Chart

The source and speed rating chart can be found here.

This writer believes that towing an RV down the road is safer at no faster than 65 mph, though. On top of the safety factor, the faster you pull that thing, the worse your gas mileage is. Look at it this way, a 500-mile trip will take 7.6 hours at 65 mph and 6.6 hours at 75 mph. Is the safety of your family and RV worth saving an hour? If you absolutely must make sure your speed needle is at the exact number that the speed limit signs state, make sure your tire is rated for that speed.

Age

Most people don’t put enough miles on their RV tires to wear them out. But tires do have an expiration date. Tires on a trailer should be replaced every 5 to 6 years. That is generally a good rule for ST or LT tires on a trailer. Trailer tires are constantly under a heavy load, and they tend to sit in storage for long periods between use, which causes them to break down faster.

Before each trip, inspect your tires for any cracks around the treads or the tire’s sidewall. There should be no bulges or defects of any kind. Remember, the 5 to 6-year rule only applies if your tires aren’t showing defects before that time. Many factors may require them to be replaced sooner.

The ST vs. LT Debate

Some RVers feel that LT tires are superior to ST tires and that no one should use ST tires. This claim can be found in many RV forums. It is usually based on anecdotal information or personal stories.

While individual stories and reviews of tires are important, it is hard to argue with an entire tire industry spanning global manufacturers and companies that say ST tires are a tool developed specifically for trailers. With tire manufacturers coming out with new ST tires with higher speed ratings, some of their arguments do not hold water.

Some RVers just want LT tires on their travel trailers and fifth wheels that didn’t come with them. On the flip side, some RVs come with LT tires from the factory. However, if you want to switch to LT tires, you must make a few considerations.

  • LT and ST tires do not have the same load rating when comparing size for size, so make sure whatever tire you choose has a sufficient load capacity for your RV. If the tires you are switching to have a higher load capacity, that does not automatically increase your GVWR. It’s never safe to overload your RV.
  • You will probably have to choose a larger tire size to find an LT tire of equal or greater load capacity. Make sure there is sufficient clearance all around the tire.
  • When you change your tire size, you will need a properly sized wheel as well. Changing out tires and wheels can be rather costly.

Conclusion

At the end of the day, it boils down to this. Tire manufacturers state that they have designed ST tires for the loads and motion that travel trailers and fifth wheels experience. Therefore, it is reasonable to assume that your best gas mileage and towing feel will probably come from ST tires, especially if that is the type of tire your RV came with. If your current ST tires don’t have the speed rating you like, or you don’t feel comfortable with the no-name brand tires that came with your rig, there are several options of high-end ST tires to choose from.

LT tires are not wrong or right for the most part. They just aren’t engineered for that job necessarily. Can you use them? Yes. If they are the proper weight rating and size for your RV. Many people run them with little problems at all, and some RVs come with them.

Should you switch to them if your RV didn’t come with them? It’s up to you but think of it this way. A rounded shovel is suitable for digging in the ground, a snow shovel is designed to glide over the top of the ground to move snow. Both are shovels, and technically you can use the smaller round tip shovel to move snow, but it won’t do the job as well as the snow shovel.

The snow shovel could be used to dig a hole, but it would be difficult, and you would probably damage the snow shovel in the process. Similarly, tire engineers tell us that ST tires were designed for the loads and force a trailer will experience. LT tires were engineered more for the loads and forces the towing vehicle will have. It’s best to always ensure that you are not only using the right tool for the job, but you are using it properly too.


About the author: Levi Henley

Levi Henley and his wife, Natalie, have been full-time RVers for over 5 years. They have also been Coach-Net customers for the same amount of time.  They travel and workcamp around the U.S. in their 26-foot Itasca Sunstar motorhome with their two cats.  They write for multiple RV-related publications and recently co-wrote “Seasonal Workamping for a Living: How We Did It.” You can follow their adventures on the road at henleyshappytrails.com 

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