For people, with age comes wisdom, supposedly. For ST (Special Trailer) tires, with age comes ozone cracking.
"Realistically, tires on boat trailers, livestock trailers, cargo trailers and RVs don't get taken off when they're not in service," says Kris Fettig, Goodyear Tire & Rubber Co.'s account executive for the RV industry. So they sit and may be exposed to harmful elements such as sunlight and high temperatures.
"Five to seven years is the service window for these tires, even though they may still have ample tread and have sat more than rolled," says Fettig.
And when trailer tires are in use, they are subject to heavy loads, the jarring effects of stiff trailer suspensions, sidewall scrub and other abuses.
Therefore, dealer recommendations on tire selection, maintenance and storage are all the more important in this tire sales niche.
Special treatment
ST tires are built to be more bruise resistant than passenger tires. One reason is that the suspensions on trailers tend to be stiffer and less sophisticated than automotive suspension systems; thus the tires must be capable of withstanding more abuse.
ST tires need stiffer sidewalls to help control and reduce trailer sway caused by heavy or high vertical side loads (caused by camper trailers and the like).
Trailer tires also are designed to offer a softer ride to protect the trailer and its contents.
"Trailer tires are designed with the idea of being a free-rolling type tire," says Dave Carper, Goodyear's tire applications engineer. "It will have less non-skid properties (and) less tread depth. It will not be designed with properties for braking, cornering and steering forces. It also has a narrower tread."
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Rick Coffey, product manager for high speed tires at Carlisle Tire & Wheel Co., says the market for trailer tires is now about 40% bias, 60% radial.
The lighter weight, lesser-cost open trailers may still be equipped with the smaller 13- and 14-inch bias tires. But the majority of 15-inch applications are radial, says Tom Beasley, vice president of aftermarket sales for Greenball Corp. "Acceptance of radial ST tires has followed behind the acceptance of radial passenger and light truck tires and therefore is becoming a dominant force in the ST market."
The market has been skewing toward radials for a while, agrees Skip Sagar, vice president of aftermarket tire sales for Titan International Inc. The reasons include radials are becoming closer to bias in price, they are becoming more plentiful, and “they track better and have more puncture protection due to the steel belts in the tread area,” says Bob Graham, regional manager for Duro Tire and Wheel. Also, the market is driven by OE trends, which is becoming increasingly radialized.
What this means for the replacement market is, "Customers are loyal to their OE tires, if they've had good luck with them they usually don't switch," says Scott Griffin, specialty tire manager for Maxxis International-U.S.A.
"Trailer manufacturers choose the tires to fit the requirements of the application," notes Carper. However, when manufacturers choose a tire for a certain load capacity and gross vehicle weight, they will often choose the minimum. "If the customer has added equipment and weight, they may go over that load carrying capacity."
Therefore, "Some customers choose to go up a size or a load range, depending on what fits," adds Griffin.
Although these tires would be more forgiving toward abuse and can carry heavier loads, one important factor to pay attention to is making sure the load carrying capacity matches that of the axles, adds Graham.
Another thing to keep in mind is that unlike other types of tires, trailer tires are run at or above capacity most of the time, says Coffey. "Correct air pressure is the key to everything. Most car tires are never run at maximum capacity like trailer tires."
