Boat Trailer Tires

Boat trailer tires differ from passenger tires, so understanding this difference you will be able to head to the fishing outing with more confidence.   To understand why there is a difference you need to think about how the load on a boat trailer is going to be different from that of your car or truck.  Standard passenger car tires or even light truck tires allow for that vehicle to turn safely, which means that the side walls must be constructed in a more flexible manner.  


The nature of the force on a trailer tire however must take into account the tendency of the load being carried to sway back and forth.  The load is anchored at the ball of the hitch, with the load or weight trailing behind by as much as 25 feet or even more.  This means you need a tire that has a stiffer side wall, one that is designed to resist this tendency – a tire specifically made as a trailer tire.


Selecting Proper Boat Trailer Tire

A reputable tire dealer will not lead you astray, but the more you educate yourself the more you will be able to discuss with that dealer what your needs will be and which tires they have to choose from best meets those needs.  Here is a typical tire code you would need to tell your dealer to help you buy your tires.

ST175/80R13C

Applicaton type Section Width Aspect Ratio Construction Type Diameter Load Range
ST - Special Trailer 175 mm 80% R = Radial 13 inches C

Trailer Tire Rating

Look for the ST rating.  This stands for "Special Trailer" tires.  It is never recommended to use a standard passenger tire.  Always look for an ST rated tire for your trailer application.


Boat Trailer Tire Size

Boat trailer tires size is determined by the size of your rims or wheels. Your rims or wheels were selected by the manufacturer of your trailer to exceed the expected needs of your boat trailer so you should replace tires that match the originals.  If you ever desire to change the rim size and/or the tire size you will need to make sure you will maintain the proper clearance between the tires and the fenders and undercarriage. This is where an expert at a trailer repair shop could really be of help.


Tire Load Capacity

The combined total weight of your loaded boat is going to be carried by the number of tires touching the ground.  Make sure that their load capacity exceeds this gross loaded boat weight.  If that weight is 5,000 pounds and you have a tandem axel with 4 tires that means that each tire needs to exceed 1,250 pounds – for example each tire should have a 1500 pound capacity and you will adequately exceed the expected load.


Bias vs. Radial Ply Tires

The main difference in these two tire types is in the direction the inner mesh is laid in relation to the centerline of the tire.  Bias tires inner mesh is laid at a 30-45 degree angle to this centerline with fiberglass belts added for strength.  Radial tires mesh is laid at a 90 degree angle with steel belt mesh added for strength. For Bias Ply tires this results in a somewhat stronger and stiffer sidewall, and are usually somewhat cheaper.  Radial tires designed tire surface does not deform as much under load as a bias tire.  Radial trailer tires are smoother and quieter and offer a bit more fuel economy.  They will also run cooler all of which may mean that for longer trailer trips on hot summer days the radial tires would provide better service. For shorter trips, on boat trailer tires that will not get many miles bias tires can be a cheaper option. Most boat trailer tires tread will not wear out before they need to be replaced. (See “Know When to Change Your Tires below".) 


Trailer Tire Maintenance

The first safety tip for boat trailer tire care is to check your air pressure in all your tires. Your tire pressure should be maintained at the maximum pressure for the tire when it is cool.  Under inflation is hard on the side walls of the ST tires and is the leading cause of tire failures. Tread is important and you should make sure your trailer tires have adequate tread.  Tire dealers use an actual measuring device that measures down to 1/32 of an inch. If tread is below that you should replace that tire. A simple method is to use a Lincoln Penny, and place the edge inside the tread of the tire.  If the tread hides even a portion of the Head of Lincoln your tread is more than 1/32 of an inch deep.

Tire Tread Depth The Lincoln Head Penny Test

When to Change Trailer Tires

Under most boat trailering conditions the life expectancy of boat trailer tires will be reached before the actual tread life wears out, unless you are a Professional Fisherman (woman) who travels hundreds of miles every weekend.  The life expectancy of most trailer tires is less than 6 years, even if not used often. Load, heat, weather elements, sun light, and time all weaken a trailer tire.  Know when you purchased your tires. Did you know each tire has a manufactured on date molded into its side wall?  For tires made beginning in 2000, there will be 4 numbers – the first two numbers tell you the week during that year they were made and the second two numbers are the actual year.  So, 1410 would mean a tire that is made the 14th week of 2010.  One should note this date at the time of purchase and make sure you are not buying a tire that is already 3 years old.  The tire in the image below was built in the 51st week of 2007.  Even if your tread looks pretty deep, if your tires are more than 6-7 years old you should consider replacing them.

Tire Codes date of manufacture Manufactured on Date

Storage and Trailer Tires

Winter storage of your Boat and Trailer would be best in an inside storage garage.  If you must store your boat outside you should cover your tires completely to avoid damaging effects of the sun. You should also make sure your tires are stored with maximum pressure.  For storage more than a couple of months, you should try to raise your boat onto blocks to avoid a 4-5 month period with your boat load all in one place on your tires.  Exercise caution if you choose to do this.  


Common Trailer Tire Brands

These 5 brands often are the first to come up when you do your search.  My experience has been with one brand which I continue to use.  Price comparisons have been close enough for me to stick with what I am comfortable with.  A tire dealer who can offer 2-3 of these brands would be a great resource to use.  Carlisle, Goodyear Marathon, Titan ST Radials, Duro, Tow Master


Other Boat Trailer Parts