Large or Small Trailer Tires: Does Size Really Matter?
Trailer tires are often much smaller than a truck's, yet they're engineered to safely carry heavy loads. The real secret isn't tire size... it's matching the tire to the trailer.
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Rated trailer tires rarely match the size of the tires on the towing vehicle. A tow vehicle must accelerate, steer, brake, and provide a comfortable ride. A trailer simply follows behind, carrying its load while resisting sway and enduring tremendous side forces during turns.
Because many trailer tires are considerably smaller in diameter, they rotate far more times over the same distance. A typical light-duty trailer tire can make nearly 50% more revolutions than a 31-inch O.D. pickup tire at highway speeds. Those extra rotations mean the wheel bearings, grease, seals, and tire casing all work harder, making heat a big enemy.
Trailer tires marked ST, for Special Trailer, are engineered specifically to carry vertical loads and maintain stability. Their stiffer sidewalls reduce sway and withstand the sideways scrubbing that occurs because trailer axles do not steer. Tire diameter alone says very little about how much weight a tire can safely carry. Load range, construction, and inflation pressure determine its true carrying capacity.
While larger trailer tires generally rotate more slowly, roll over bumps more smoothly, and often run cooler on long highway trips, smaller trailer tires perform exceptionally well when they're the correct size and load rating for the trailer. Proper cold inflation pressure, staying within the tire's speed rating, maintaining wheel bearings, and avoiding overloads contribute far more to safe towing than simply installing larger tires.
Another overlooked factor is trailer attitude. A trailer that rides level distributes weight more evenly across its suspension and tires, improves stability, and can reduce sway. Adjusting the hitch height so the trailer travels as close to level as possible is one of the simplest improvements a trailer owner can make.
For a deeper look at why trailer tires require higher air pressure, what the ST designation means, how speed ratings affect heat buildup, and why trailer tires fail, watch our companion HIPS episode: https://youtu.be/wW-YfJBilzE
Sometimes the smallest tires on the highway are doing the hardest work.
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