Are you the proud owner of a new or pre-owned boat? Getting out on the water for some fun in the sun is a great way to enjoy good weather.
However, when it comes to getting your boat to the water, you’re going to need a trailer. Most boats come with trailers included in the package, regardless of whether you’re buying your boat new or used.
Trailers are essential for moving the boat around, and they require the same care and maintenance that you put into your boat. One of the common mistakes new boat owners make is failing to use the correct tire pressure in the trailer tires.
This guide gives you everything you need to know about using the correct boat trailer tire pressure.
Contents
Why Is Tire Pressure Important?
Trailer tires require higher pressure levels than standard motor vehicle tires, usually in the range of 50 to 60-psi. Most trailer tire manufacturers print the related tire pressure into the sidewall for easy reference, but you might come across a tire that doesn’t have this feature.
If that’s the case, you’re going to have to learn how to inflate your tires to the correct pressure. The tire’s pressure rating also determines the max-load the tire can support before it bursts. You’ll need to ensure your tires have the recommended pressure, or you risk reducing the load capacity of your trailer.
Failing to inflate the tire to the correct pressure reduces the load capacity and diminishes its service life. Under-inflated tires will cause damage to the sidewalls and the tire’s structural integrity, resulting in it falling apart – likely when you’re on the road at high speed towing the boat.
If you experience a blowout at speed, you could wind up in a dangerous scenario resulting in an accident.
- For example, a single-axle boat trailer featuring a 2,490-pound trailer and cargo uses ST175/80R13C tires with a maximum tire psi of 50-lbs. At the optimal inflation rate, each tire can handle 1,360-lbs of weight or 2,720-lbs over the entire axle load.
- Reducing the tire pressure to 40-psi, we find that the individual load rating on the tire drops to 1,190-lbs, or 2,380-lbs over the entire axle, leaving you with a 110-lbs difference between the optimal pressure rating for the tires.
- Dropping the pressure further to 35-lbs, we find that total tire capacity across the axle drops to 2,200-lbs. So, if the loaded boat weighs 2,400-lbs, you’re placing too much demand on the tires, and you can expect them to fall apart on your when you reach speed.
How Does Friction and Kinetics Energy Affect Tire Pressure?
You might wonder what will happen if you inflate the tire to the max rating and how it will respond when it heats up. After all, air expands under heat, right? So, won’t the tire explode when it gets over-pressurized?
The reality is that the air pressure will rise as the tire warms up. However, the increase is negligible, rising by only one or two psi for every ten degrees in temperature change. If you’re driving in warm weather, fill the tires to 2-psi below the max rating to compensate for the increased pressure caused by friction.
Tips for Properly Inflating Your Trailer Tires
All trailers come with a VIN plate, sticker, or tire-and-load plate or stickler. Most manufacturers place the sticker on the inside frame rail, so look around for it. These plates or stickers give you the correct tire size and the GVWR rating for those tires, along with the recommended psi rating.
If you’re buying a preowned trailer, check the plate or sticker to see if the trailer has the correct size tires. Many owners fit the wrong tires to the trailer without realizing it. If you can’t find the plate or sticker, call the manufacturer and ask them for the information.
Check the Tire Before Fitting It To the Trailer
The sidewalls of trailer tires usually have all the information you need on the tire’s size, rated capacity, and function. There are specific tires designed for trailers, and you’ll see that they have the letters “ST” molded into the sidewall for easy identification. “ST” stands for “Trailer Use Only.”
ST tires have reinforced sidewalls to compensate for handling heavy loads. The reinforcement prevents the sidewalls from deforming as you corner with the trailer.
We recommend going with radial or bias-ply tires as the best choice for your trailer. Bias-ply tires have stiff sidewalls, and they are less expensive than radials. However, they are only suitable for short-distance use.
Radials are the best option if you’re going on a journey that takes longer than an hour to reach your destination. Radials offer less heat accumulation, higher load capacity, and lower road noise. As a tip, never place two different tires on the trailer. Using a radial on one side and a bias-ply on the other will lead to disaster. Also, we recommend replacing both tires at the same time.
How Do You Know When Trailer Tires Need Replacement?
Tires give you plenty of warning signs that it is time for a replacement. Over-inflating the tires causes them to wear down the tread in the center rather than evenly distributing the wear across the entire surface. Underinflating the tires causes wear on the outside edges.
Inspect the tires before heading out on your journey to prevent any nasty surprises on the way to the venue.
Some of the other signs that it’s time to replace the trailer tires include the following.
Tread-Depth
You can use a Lincoln penny to check the tread depth on your tires. Place the penny upside down on the tread. If you can see the top of Lincoln’s head above the tread, it’s time to replace the tires. Running tires with low tread reduces the tire’s grip, resulting in slip-outs, especially in wet weather.
Tire Sidewalls
Look for spiderweb cracks on the sidewalls, it’s a sign of rot, and you’ll need to replace the tires.
Valve Stems
Faulty or worn valve stems cause leaks in the tire pressure, resulting in flat or underpressurized tires. Check the valve stems by pressing a finger to one side of the stem, and listen for air escaping from around the valve stem.
In Closing – Check the Tires Before You Buy
If the trailer has worn tires, it’s going to cost you to replace them, and tires are not cheap – especially good-quality radials. When buying a pre-owned boat, inspect the trailer and the tires.
If you find the tires are worn or cracked, negotiate with the owner to drop the price to account for the expense of buying new tires, they’ll usually be happy to accommodate your request.
When purchasing your new tires, ask the dealer if they sell tire covers. Fit the tire covers after you park the trailer at home. The covers stop the sun’s harmful UV rays from weathering the rubber on the tires, reducing the chances of spiderweb cracks appearing on the sidewalls.
Keep the tires in good condition by adding a tire restoration product to the side walls. However, please don’t get it on the tire’s tread as it may cause the tire to slip out when cornering the trailer.
