Trailer Tires are Special

Trailer tires are a different animal. Sure, they’re round, black and covered with tread just like the tires on your cars, pickups, and motorhomes. But when it’s time to go to work, trailer tires have a different mission.

“Passenger and light truck tires are designed for entirely different applications than a trailer tire,” says Dave Carper, applications engineer at Goodyear. “They have completely different performance criteria.”

A trailer tire is engineered and designed for carrying heavy loads and braking, adds Rick Coffey, product manager at Carlisle Tire & Wheel Company. It’s a free-rolling tire that directs the trailer straight down the road. It doesn’t need to have features that provide handling performance such as cornering or steering, nor does it need to transfer any torque, which is in complete contradiction to the tires mounted on the towing vehicle.

When you take a closer look you’ll see some things about trailer tires that set them apart from passenger car or light truck tires.

The tread is shallower. Tire people refer to tread depth as “non skid.” It’s shallower because it doesn’t need to grip the road surface as aggressively as vehicle tires do for accelerating and turning. What’s more, a shallower tread combined with a different rubber formulation helps the trailer tire run cooler, and that’s a benefit for trailer duty where loads can be heavy and air circulation may be restricted.

A trailer tire will also have a stiffer sidewall. Since a passenger or light truck tire isn’t required to carry as much weight, it can have more flexible sidewalls that will soften up the ride and make your trip more enjoyable.

“These design features also make it easier to twist and turn your trailer as you maneuver it into a campsite or onto a parking pad,” adds Kris Fettig, original equipment sales executive for RVs at Goodyear.

These differences are unique enough to warrant a special industry wide designation. Tires labeled as ST (Specialty Tire) are designed specifically for trailer duty and are recommended whenever you need to replace your trailer tires.

Note that these qualities that make ST tires well-suited for trailer service also make them less than ideal for vehicles: Don’t use ST tires anywhere other than trailers.

Select a tire to carry the load

Manufacturers including Goodyear and Carlisle offer a variety of trailer-rated ST tires ranging from 13- to 16-in. in radial and bias-ply designs.

Select trailer tires based on the maximum load they’ll be carrying. All tires will have a maximum load carrying capacity so make sure you don’t exceed their limitations. If you know the weight of your trailer, consult the load and inflation tables published by the tire manufacturer or provided by your vehicle manufacturer. If you haven’t weighed your trailer, use the weight listed near the outside left front of your trailer. Keep in mind that personal belongings such as food, clothing, water, fuel and supplies add weight to the vehicle.

When choosing between radial and bias-ply tires take into consideration that although bias-ply tires are more economical initially, they won’t last as long.

“Because of their construction, bias tires generate more heat,” says Coffey. “A radial tire has less rolling resistance and it dissipates heat faster and more efficiently so it runs cooler. If they’re properly maintained and pumped up to the proper psi, radials will last longer and you’ll get better gas mileage in your towing vehicle.”

Trailer tire tips

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