While there are differences between car and trailer tires, they look the same and operate on the same principles. Because of this, one would think that car tires can easily take on the job of a trailer tire. I was about to use some car tires I had laying around the house but after doing some research decided against it.
So can you use car tires on a boat trailer? The general answer is yes, but this is one of those cases where just because you can do it does not mean you should. A trailer, especially a boat trailer, is a piece of specialized equipment designed to do only its intended job. The tires used in these trailers have a distinct difference in design than that of a run-of-mill car tire.
Using non-specified tires on trailers is the number one cause of tire blowouts on trailers on the road today. Spending a few minutes of your time knowing the difference between car tires and trailer tires can help make sure you are not one of those suffering the same fate.
Knowing The Difference
There are several reasons why one might use a tire that is not according to specifications. You could have a pair of extra tires lying around the house, hand me downs from relatives, or you are just the type who does not want any extra stuff to go to waste. Whatever the reasons you may have for having car tires that you can use on your trailer, you have to know whether or not it is safe to do so.
A mistake many boat owners have is that they often think that because they own a relatively lightweight boat, it makes it okay to use just about any tire on trailers. The main thing that separates the two kinds of tires is the strength of the sidewall on trailer tires. Ordinary tires have caused many a blowout on inconvenient times on road trips. These blowouts could have easily been avoided should the correct kind of tires are used on their trailers.
Tires are classified as P, LT, and ST, and that is Passenger, Light Truck, and Special Trailer tires, respectively. ST tires are rated to have 10% more loading capacity than Light Truck tires and 40% more than Passenger car tires (Source: West Marine). These numbers do not lie, and Boat U.S. also reports that tire problems are the number one reason for people calling in for assistance on their trailers.
All these facts combine into information that will lead you to decide not to use tires other than ST tires on your boat trailer. They have stiffer sidewalls and are typically narrower than regular tires. These tires are designed that way for fewer sideways movement and are equipped with shallower treads less wiggle while on the road. The bottom line is that it is always better to be on the safe side.
Are There Exceptions?
Perhaps the only acceptable reason for using car tires on a boat trailer is if you are only doing it temporarily on an emergency to get from point A to point B but, once they serve the purpose, car tires should be changed back to trailer-rated tires. Using non-standard tires for boat trailers has accompanying risks. It compromises your safety and others, and as such, the choice should be obvious.
Furthermore, if one absolutely must use car tires, at the very least, check its load rating, pressure, and general condition before usage. Making sure that the car tire is as near as possible to the recommended specifications of the trailer is one way to an uneventful ride. Specifications, in this case, means tire pressure, tire size, as well as recommended speed.
Flexing Tires Are Not Suitable For Trailers.
Car tires are designed to carry passengers comfortably, with emphasis on ride comfort. This makes them less stiff than ST tires making them flex on heavier loads. Trailers are made with higher centers of gravity and are prone to overturning at speeds. Trailer tires are created with stiffer sidewalls specifically to counteract this tendency, therefore putting in wheels that flex is not sounding very good at all.
In addition to reinforced sidewalls, trailer tires are also manufactured to be narrower and with shallow treads to reduce load sway and movement further. Besides, the suspension in a trailer is not as good as those in an automobile, making them even more prone to additional movement while underway.
Air Pressure Is Super Important.
Unlike car tires, whose psi hover around 30-35 psi, trailer tires usually will be about 50-65 psi. Tire pressure determines how heavy of a load can that trailer carry and define it’s carrying capacity. It is a good idea to know exactly how much your boat and your trailer combined weight when optimizing air pressure on your trailer tires. Most ST tires run on the maximum PSI specified by the tire manufacturer.
Pulling your boat trailer around with an under or over-inflated trailer tires will compromise the load capacity of the entire trailer. It is important to remember that both overinflation and underinflation can lead to overheating tires. Overheated tires can lead to blowouts and on to accidents. Fortunately, all new trailers will have a tire-and-load sticker that states the exact specifications regarding the tires’ correct size and rating.
Keeping It Within Its Speed Limit Rating
The industry standard on all Special Trailer tires is that it should run on 65mph under normal inflation and road conditions. Running above this speed restriction is not optimal, especially when running with a load. This recommended speed is based on how safe a vehicle with a trailer can go without endangering anyone on the road.
It is also a must to remember that these limits are not targets, so it doesn’t mean that just because the limit is 60 mph, you should maintain it as such. It’s all but prudent to drive as fast or as slow as the conditions allow while making sure that it stays within the limit. Heavier vehicles also need a longer stopping distance, and it is always a good idea to take it slow.
Prevention Is Always A Good Thing.
Trailer related accidents or inconveniences can mostly be prevented by simple maintenance and knowing the correct tolerances of your equipment. One of the first things you can check is your tire’s inflation pressure while it is still cold, meaning it has not run any distance yet. Tire pressure is clearly marked on your tires, check all of your trailer tires to make sure they are even on all tires.
Do a walkaround on all tires to check for any structural damage or cracks on the sidewalls, as well as checking your tread depths. Traction is dependent on this depth, and we do not want them to shallow as to almost be non-existent. This is also as good a time as any to check valve stems.
Trailer tires often sit for prolonged periods of time in one position, and continuous exposure to the sun’s harmful UV light can make the rubber brittle. It is a great idea to put covers on the trailer tires if you are going to leave it out parked for a while. For the opposite extremes of weather, such as wet or frozen conditions, it is better to just entirely remove the tires and store them in a protected space.
Related Questions:
Do ST tires last longer than regular tires? Special Trailer tires are manufactured with tougher and heavier duty materials than those of regular tires, and they are expected to last significantly longer than conventional tires. Trailer tires also experience less traction as they are just meant to follow a lead vehicle. This makes their wear and tear relatively on the minimum compared to the ones pulling the trailer.
What about LT tires? Light Truck tires are increasingly becoming popular as alternatives for the narrower ST tires on trailers. Sure, they may look cooler, but LT designated tires have softer sidewalls and deeper treads that make them flex and sway on the road. These movements are a no-no when hauling trailers, especially a boat trailer at that.
Will it overinflate if run on max PSI? Overinflation is one of the most common reasons for tire blowouts, and to avoid this, make sure to make it a habit to check them via a gauge (never just eyeball them). Sometimes both wheels may look the same but will have different psi’s when gauged.
ST tires are always recommended to be inflated at its maximum psi setting and to avoid overinflation, put air into them while they are still cold and before running out of the garage. Cold inflation pressure should not exceed beyond 10psi above the maximum recommendation.
Wrapping up
Aside from the glaring safety issues for not using the recommended trailer tires, trailers are more stable and easier to pull when using Special Trailer tires. Stiffer sidewalls help in negating trailer sway. Trailer tires will also last longer than their conventional counterparts and can help you save time and money in the long run. Here is a link to the best selling trailer tires on Amazon.
