Anyone who has had to replace tires on his trailer has probably wondered why they are typically more expensive than economy auto tires, and what the major differences are. What pressure should you run them at? Why does it seem like you are always replacing them? What are the reasons for uneven tread wear?
Trailer tires are not designed for traction, except when braking, and do not have to meet the all-weather standards of automotive tires. They are designed with a harder and stronger sidewall to help reduce sway. Automotive tires with softer sidewalls will magnify trailer sway problems.
Trailer tires come in two basic types, Bias-Ply and Radials. Bias Ply tires have nylon or Polyester cords criss-crossing from bead to bead, giving the sidewalls the same ply as the sidewalls and making for a very stiff tire sidewall. The cords are also larger than comparable passenger car tires to meet load rating requirements and reduce wear. This maximizes resistance to sway. Bias-Ply tires are typically used on trailers that do not get high mileage-use, such as boat and utility trailers. Driving long distances non-stop at highway speeds can break down bias-ply tires quickly and cause “cupping” which is uneven wear on the tread, due to the tires’ hard sidewalls and subsequent inability to expand properly when they get hot.
Radial tires have steel belts below the tread and sometimes the sidewalls, and softer sidewalls, making them excellent choices for long distance towing, but also increasing the chance of sway on improperly balanced or loaded trailers. They have better traction than bias-ply, which is irrelevant in most cases except for sudden stopping. They are always more expensive than their bias-ply counterparts, but both tires carry the same weight rating at similar load ranges.
Trailer tires are made NOT to wear out! “ST” tires (for trailers) contain chemicals in the rubber compounds to resist weather and sun damage. The most common reason for tire failure is underinflation. Trailer tires are designed to be used only at their MAXIMUM inflation. Trailer tires take a much higher psi than automotive tires. The stiffer walls are designed to withstand the shocks of road hazards even though the trailer suspension is inferior to an automobile’s. A trailer tire’s lifespan is expected to be anywhere from 5,000 – 12,000 miles.
Trailer tires are designed to be replaced every 3-5 years. Time and elements reduce a tire’s weight rating by about 1/3rd in approximately three years. It is suggested that you replace trailer tires every 5 years regardless of visual appearance.
ST Trailer tires are designed to travel at a maximum 65 MPH. As tire heat builds up, the tire starts to weaken and disintegrate. Running on a hot, weakened tire results in costly blowouts.
LT trailer tires are NOT the same as “Light Truck” tires. The “LT” on trailer tires specifies a load range. Trailer tires cannot be used on automobiles.
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Rob Wiseman
R W Trailer Parts, LLC
Linthicum, MD
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