TRAILER TIRES
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Can I use any tire on my trailer?
Trailer Tire are much different than passenger tires. Passenger tires must maintain traction during all driving conditions; rain, sun, stopping, turning, accelerating, etc. therefore they must have more flexible sidewalls to maintain traction on the road or as we call it in the tire business, “increasing it’s footprint”. Since trailers have free rolling axles and there is no torque on the tires, the need for a flexible sidewall isn’t necessary. Instead, having a stiff sidewall to reduce sway and flexing is more important. The standard classification for passenger tires will be (P) for Passenger and (LT) for Light Truck – meaning they have the flexibility of a standard car tire but are rated to carry a heavier load. Whereas, trailer tires made for a free roiling axle will be classified as (ST) for Specialty Trailer.
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Understanding Load Range
The load range or ply rating branded on a tire’s sidewall helps identify its strength and ability to contain air pressure, the more air pressure (PSI) in the tire, the more weight the tire can carry. A standard passenger tire will have a B rating, whereas light truck tires range from C to G, the most common being load range E. Specialty Trailer tires also range from B to G, with the most common being D and E.
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Why an ST?
ST tires have about 10 percent more load capacity than an equivalent LT tire when each is filled to its maximum PSI rating because the sidewall is made stiffer. On a passenger car, ride comfort and traction are important, therefore the sidewall must remain flexible. On a specialty trailer, load capacity and stability are important. Therefore, not only are the sidewalls more sturdy on ST tires, but the tread is shallower. This also helps reduce sway and keeps the tire running cooler to prevent sidewall blowouts and increase longevity. The elimination of torque on the tires, eliminates the need for additional tread depth. Remember, P & LT = flexibility :: ST = stability.
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Overloaded and Under Inflated
Being overloaded is a major cause of a tire failing. It is important that you weigh your trailer fully loaded before making a tire decision. All tires have a load inflation table (see below) to ensure it is rated to properly handle the weight of your trailer. Being overloaded causes heat to built up and puts an excess amount of strain on the tire’s sidewall, increasing the risk of blowouts.
The most common cause of tire problems is under-inflation. It is estimated that a trailer tire that is 20 percent under-inflated will cut 25 percent off its lifespan. Under-inflated tires also affect fuel efficiency by as much as 10 percent due to added drag. However, under-inflation is the #1 cause of tire failures. Remember above, the more PSI in the tire, the more weight the tire can carry – this means when you’re under-inflated or don’t have enough PSI, you’re OVERLOADED and increasing your likelihood of failure.
