On/off-road tires must strike a compromise between traction, durability and longevity. "Fuel efficiency, tread life, casing durability and other factors can have a direct impact on operating cost," says Chris Tolbert, business segment manager, Michelin Americas Tires. "By selecting the best tire for the application, on/off-highway fleets can ensure their operating costs remain low."
Many different types of tires are available. "There are all-position tires - capable of being used in steer, drive or trailer positions - and tires made specifically to give better traction in drive positions," notes Tim Miller, Goodyear Tire & Rubber.
Yet, a common mistake is assuming one or two different tires will fill the needs of every truck in the fleet. "If some trucks travel frequently on the highway and others are mainly off road," Millers notes, "the same tire, or tires, might not deliver the best performance (tread wear and durability)."
Match to operating conditions
It's all about choosing the most appropriate tool for the job. "Most people don't try to pound a nail with a screwdriver, and neither should they expect good results if selecting the wrong tires," Tolbert asserts. "On/off-road tires face specific challenges and dangers that must be addressed in the tire design and construction to make sure the tire's life and performance will be maximized."
Consider the percentage of time the vehicle will spend on- and off-highway. "A tire that is designed mainly for off-highway use will wear more quickly than an over-the-road tire when the vehicle is used in mainly highway situations," Miller states.
Also evaluate the type of terrain or application the tire will experience off road. "Knowing the type of environment will help determine the level of traction that is needed for the vehicle to operate," says Tolbert. "This information will also dictate the amount of tread and sidewall protection the tire will need to stay up and running. The on/off-road tire should also have a compound designed to combat the aggressive nature of the application."
The truck's configuration makes a difference, as well. According to Miller, single drive axle vehicles require more traction capability from tires than tandem drive axle vehicles.
Another consideration is puncture resistance. "Tires with built-in sealants can greatly reduce vehicle downtime and the associated costs," says Miller.
Compound and casing trade-offs
According to Tolbert, rubber compounds play a significant role in protecting a tire from damage and enabling it to perform at a high level. They are formulated to address the specific needs of a range of different applications.
"Certain compounds are better suited for predominantly highway use," he explains. "Other compounds, whether in the tread or sidewall areas, are designed to resist chipping, chunking, cuts and punctures from debris in the harshest of off-road applications."
To maximize longevity, it's important to apply the right compound to the application. "Tires designed for highway use tend to chip and chunk when exposed to off-highway situations for long periods of time," Miller points out. "Conversely, a tread compound that resists chipping and chunking will not deliver long tread wear if used in an over-the-highway situation."
The design of the casing is also critical. "On/off-highway tire casings are built to be flexible and resilient, so the tire 'envelops' or wraps around an obstacle," notes Guy Walenga, director of engineering, Commercial Products and Technologies, Bridgestone Americas Tire Operations, LLC. "Flexible belt packages are built to use steel cables made with fewer twists and more space between the cables, while split-belt construction keeps the footprint flexible."