10 Things You Need to Know About Boat Trailer Tires

Although your boat is an essential part of fishing or watersport adventures, how you deliver it to the water is crucial, too. The right trailer is vital for transporting and protecting your boat, so the boat trailer tires should rank on your list of necessary items, too. Here are ten things you need to know for safety and efficiency when maneuvering your boat around town on a trailer.

1. Your Trailer Needs a Certain Type

It may be tempting to put any tire that fits on your boat trailer, but there are specifications in place for trailer tires. Special Trailer (ST) tires are the only type you should use on your boat trailer unless you’re willing to risk damage or potentially an accident.

ST tires have robust sidewalls to handle lots of weight, which helps avoid tipping your boat onto the road while cornering turns. Radial and bias-ply tires are both available for trailers, with radials working better for longer trips and bias-ply ideal for short trips to your local waterways.

Before you purchase a trailer (or even a boat), consider the costs associated with the boat plus trailer and tire costs. Before you start estimating your investment with a boat payment calculator, think about how you’ll transport your new toy and plan accordingly. Trailer tires are an essential component of your boating setup, and it’s not worth the risk to gloss over that part of the venture.

2. Measurements Do Matter

Just like any vehicle, you should only use four (or more, depending on your trailer’s size) of the same tire for your boat trailer. Therefore, measurements matter when grabbing a set of tires. Make sure to look at the ST designation for Special Trailer, as these are tires specifically for transporting trailers and goods.

Also look at the tire width (measured in millimeters), the height/width ratio, the letter designation (R for radial or D for diagonal/bias ply), and the wheel diameter—all in that order along the sidewall of the tire. The information tells you what type of replacement tires you need and indicates how heavy a load the trailer can manage. Ignoring that information—or misunderstanding it—can mean problems with more than getting from point A to point B.

3. Proper Inflation is Key

Correct tire pressure is critical no matter your load or vehicle type. And when your personal watercraft is in the trailer, you should check your tires’ inflation even more carefully. Boat trailer tires need to be able to handle bumps in the road while cushioning your boat’s ride. Filling them to the specified PSI is a step in the right direction.

Make sure to check the pressure regularly, too, as PSI can change with weather conditions. For example, if you fill the tires with air when it’s hot outside, cold weather can make them lost pressure. Therefore, checking pressure frequently and adjusting as necessary should be part of your boat transporting routine.

Your spare tire should also have regular pressure checks in case you wind up needing it during your trip. Even if it’s a short drive to launch your boat, you don’t want to have to change a tire or wait for a tow truck with the entire setup behind your towing vehicle.

4. Always Follow Load Limits

Load range is one of the aspects of boat trailer tires that affects how much you pay for a set. But beyond pricing, load limits are relevant because too low of a limit and you could blow out your tires just by driving a short distance.

Load ratings range from B to F, and those ratings correlate with a specific tire ply rating and weight limit. When considering load limits, you must factor in the weight of the boat, its engine, the trailer itself, the fuel, and any equipment you have stowed inside the boat.

In general, it’s preferable to use tires with a higher load rating than you expect to need, particularly when you are looking at your boat’s gross weight. Make sure to factor in equipment and other weight to get an accurate idea of what the total load will typically be.

5. How to Check for Wear

Most vehicle owners are familiar with the penny test, but here’s a reminder to use the same technique with your trailer tires. Tire tread depth should be around 4/32 of an inch deep; when sliding a penny into the grooves (Lincoln head down), you shouldn’t be able to see all of Lincoln’s head.

If you drive with tires that are bald or nearing bald (anything under 2/32 of an inch or below), you risk not only your tires and trailer but also your boat. And with new boat prices being what they are, you’re better off purchasing new tires instead.

Other signs of wear include cracks from sun damage or bulges from too-high pressure (often brought on by heat). You shouldn’t tow a trailer with damaged tires, so checking for this type of wear is a pre-trip must.

6. Regular Rotations Might Help

Depending on the size of your boat trailer, it may need regular rotations and tire balancing. For smaller trailers (single axle), you probably won’t need rotation, unless you notice odd wear patterns or other issues.

In general, common issues like filling tires to the incorrect pressure, exceeding load capacity, and trailer misalignment can cause irregular or uneven wear. Rotating the tires won’t help those scenarios, as the damage is already present, so you’ll need to replace your tires before investigating any structural problems with the trailer.

7. Environmental Exposure Hurts

While you probably don’t leave your boat uncovered in the sun for weeks on end, it’s also crucial to consider the environmental exposure your tires get. Heat and abrupt changes in pressure can cause your tires to crack and begin to disintegrate and sitting in one place all the time only exacerbates the issue.

If possible, store your boat and trailer inside a climate-controlled garage or at least in the shade and away from the rain. If not, consider covering up the tires (tire covers are widely available) or at least moving the trailer periodically throughout the off-season.

Sun and moisture are two of the biggest issues with tire wear and protecting the trailer’s mobility requires a bit of forethought. To ward of moisture damage, try to park the trailer on a dry surface such as concrete or wood (rather than grass or dirt/mud) or remove the tires entirely when you store your boat.

8. Tires Aren’t Ageless

Tires may not necessarily have an expiration date, but you should know your tires’ manufacture date and recognize that they won’t last forever. Even if you properly inflate them, protect them from direct sun and other conditions, and never overload them, your boat trailer tires will eventually require replacement.

Even though trailer tires often see fewer miles than vehicle tires, that doesn’t mean you’ll only ever need one set of tires for your boat trailer. In fact, they can sometimes wear out sooner than vehicle tires—even with lower mileage—because of environmental conditions.

Look at each tire for its date of manufacture (it’s a Department of Transportation—or DOT—timestamp). In conjunction with the mileage you put on the tires, the age can also indicate when it’s time to replace them.

9. Used Tires Aren’t Always Ideal

Just like buying a used boat, grabbing used tires may not always be ideal. When you purchase anything used, you run the risk of having it malfunction—and with no recourse. It’s especially challenging with tires because there’s no way of knowing what type of storage scenario they were in or whether they have already been through weathering and other trials.

Even used tires you keep in your own climate-controlled garage can prove a hazard once you (and your boat) are on the road. Keep in mind the benefits of buying new tires, and shop used carefully—or not at all. After all, you can check the performance of say, used outboard motors, but there’s no way to verify a tire’s performance without taking it out on the road.

10. There Are Tire Monitoring Options

Checking tire pressure regularly should be a priority for both your boat trailer and your towing vehicle. But if the idea of manually checking every tire each time you roll out of the garage is too much, consider investing in a tire pressure monitoring system instead.

Tire pressure monitoring systems use tire stem caps with technology inside; affix the caps onto your tires, and the receiver will display the pressure and even provide alerts when attention is necessary. Systems for boat owners also work in water, ideal for seamless and worry-free launching.

With the costs of boat insurance, trailer registration, and the cost of the boat itself, there are a lot of expenses associated with boating. That said, taking proper care of your trailer tires can help keep costs down and avoid disasters which will put a dent in your savings.