What Pressure Should My Tires Be for My Boat Trailor?

When you think about your boat, you probably almost exclusively think of using it on the water. Of course, this makes total sense, but when you own a boat there is more to think about than just sailing. For example, when you need to transport your boat from point A to point B, what do you do? Hook it up to a trailer! Boat trailers allow you to take your boat with your anywhere on highways and roads, so you can explore other bodies of water other than those near you. Of course, when you have tires there is always the possibility of something going wrong, like a puncture or deflation. When something happens to your tire pressure, you may not know how to get it back to the right place. In this post, we’re going to run through what you should know about boat trailer tires, as well as their perfect pressure.

Boat Trailer Tires and Why They Are Different

The biggest misconception about boat trailer tires is that they are just like every other tire, or more specifically, just like car tires. The truth is that boat trailer tires are actually an entirely different animal than car tires. If you did not know this, it might explain why you’ve found yourself on the side of the road changing your boat trailer tires more times than you can count. Of course, you are not alone in this. Boat U.S. has reported that most of the calls to Trailer Assist are about boaters having tire trouble more than anything else. With this in mind, it casts complete clarity on the fact that boat trailer tires require special care that car tires do not. The sooner boaters know this, the less time they have to spend changing tires or calling AAA for roadside assistance.

The main difference between boat trailer tires and car tires is that boat trailer tires do a lot less. They do not steer, do not transfer power from the engine to the road, and cannot be maneuvered to swerve and avoid the different obstacles that come up on the road. Car tires do all of these things and more, so it makes sense that they are a bit sturdier and go longer without incident than boat trailer tires.

Boat trailer tires are also known as Special Trailer Tires (ST), and these are designed specifically for boat trailer requirements. They come with stiff sidewalls which help prevent the rig (boat) from swaying. In addition to this, they can carry heavy loads with 10% more load capacity than truck tires and care tires. As they are designed for trailer wheels, they are narrower, have shallower treads, and run cooler.

Tire Pressure Recommendation

Since your boat trailer tires have a large burden to carry, you want to ensure that the tire pressure is up to the challenge. Your trailer tires should always be inflated to the maximum psi, which should be indicated on the tire itself. Regardless of the load of the trailer, your tire should still have the information you need. Be sire not to over-inflate or under-inflate the tire as this can make the trailer less stable. As tire trailers are made with a thicker sidewall, they are designed to handle a more “vertical load.” If the tires are underinflated, the thicker sidewall can overheat which will result in tire failure.

This useful chart will help you decide how much pressure your boat trailer tire needs depending upon its size.

Extra Tips and Issues to Look Out For

Changing Your Boat Trailer Tires

To maintain optimal tire pressure, you also have to really care for your tires. Poor care can lead to other issues that can jeopardize tire pressure. For one, you should never keep your boat trailer tires for longer than the specified lifespan. Most all trailer tires should be replaced after 3-5 years of use. Even if they seem to have a lot of life left in them, going over the time limit could lead to oxidation of the tire’s rubber.

Car tires get worn out after a certain amount of driving, but for boat tires, the culprit is oxidation of the rubber. Unlike car tires, your boat trailer tires typically sit in the same spot for long periods of time. In short, your boat trailer is likely not in use all that often, which means over-use is virtually impossible. Since your trailer tires spend most of their time sitting, the average boat trailer tires may only travel 10,000 miles if that per year. So, how does oxidation happen?

UV radiation from the sun, exposure to ozone from exhaust does a lot of the damage. These factors cause serious exterior damage to the sidewalls of your boat trailer tires. In addition to these, oxygen from pressurized area will create damage from within the tire. This is even more dangerous because it is an unseen issue that can grow over time with you being none the wiser. What’s more, there’s not many ways to detect this, which is why replacing your tires after the allotted amount of time is so important. 

Avoid Overloading Your Trailer Tires

As mentioned, one of the biggest issues for boat trailer tires is under inflation. However, the problem itself is a result of under inflation. What is especially frightening about an under-inflated tire is that you won’t always know how to identify this as the issue. Due to the sidewalls of the tire, the tire won’t sag when under-inflated like a car tire will. So how can you tell? When your trailer is not performing as it should. Your boat trailer may not handle well as you’re on the road, which cause stress to the tires (and cause them to overheat). The only accurate way to find out if your tires are under inflated is to take them to a gas station and get the psi checked. Your psi can be slightly diminished or dangerously low, but by just looking at the tires you wouldn’t know. Before loading up your trailer for a long trip, always check your tires!

What Tire Type?

There are two main boat trailer tire types to choose from: radial tires and bias ply tires. Each come with their own set advantages, making your choice purely based upon what you need for your boat trailer as well as the best fit for the trailer itself.

  • Radial Tires: Radial tires contain plies that run across the tire and belts (that are usually made of steel) running underneath the tread around the boat trailer tire’s circumference. These tires are best for “tread wear” and will last, on average, 40,000 miles. Unfortunately, radial tires are highly susceptible to oxidation of the tire rubber. On the brighter side, they are less likely to develop flat spots on either side when they are parked in the same position for a long amount of time and will typically run cooler on long trips, adding to their overall longevity. Some manufacturers recommend this tire type for their trailers, so you have some so there is not a lot of guess work when it comes to choosing this option. However, if the manufacturer does not specify on using this tire, you can consider your trailer’s handling as well as the amount and distance you travel each year to help you decide.
  • Bias Ply Tires: Bias ply tires have plies that run at a 30 degree angle. Their sidewalls are stiffer, which makes them more secure for swaying rigs. In short, they’re much better for carrying heavy loads. While radial tires will last a long time, bias ply tires tend to last an average of 12,000 miles. Of course, while radial is good for tread wear, bias ply tires are a bit more impervious to oxidation (though not forever!)

Most people tend to choose the radial tires over the bias ply tires, but the choice is totally up to you and what you need out of your trailer’s performance. Of course, you should never mix and match tires--choose one type and stick with it! 

Tire Safety for You, Your Boat, and the Road

Now that you know the recommended tire pressure (one the reaches the indicated psi), and the tire types to choose from, the only thing left is some standard road safety.

As mentioned already, knowing the correct tire pressure is not enough. You must also focus on maintaining tire pressure at the maximum recommended PSI. This will ensure cool running, proper load carrying, and the lowest rolling resistance, all of which promote higher safety!

Each tire has a valve stem that comes with a cap - be sure that the cap it kept on at all times to avoid contamination of the internal rubber valve. This will help stave off internal cracks and wear and tear. Like with your car, always carry a spare tire at optimal psi pressure just in case.

Even though your boat trailer is not like your car, the same amount of care must be shown to the vehicle. Tire pressure, proper care, frequent safety checks, and more are important parts of maintaining your own safety and the safety of others on the road. Now that you have the information you need, we hope you have safe and enjoyable travels as you head out to your next sailing adventure.