As tractor companies compete to claim the lightest footprint and the least soil compaction, some are adding more rubber and reducing recommended tire pressures significantly.
For example, John Deere's new increased-horsepower 8020 series tractors, which it introduced this summer, feature the ability to install larger, taller tires. A new 120-mm-dia. axle handles the increased load and enables factory-installed rear triple tires as an option. John Deere claims the extra tires give the wheeled 8020 the ability to pull more and tread almost as lightly as a rubber-tracked T-series tractor.
The large mid-frame will allow larger tires for increased traction, flotation and load-carrying capacity. The large size also enables increased fuel capacity to 160 gal. And if you ask Reed Turner, an engineer with the AgTech Center in Lethbridge, Alberta, that's a good thing, considering that the tractor will probably need more fuel to turn all its rubber.
In fact, Turner says triple tires may be going too far. In some cases, he says, the extra rubber may be unnecessarily costing extra fuel. So you need to weigh the resultant fuel costs against the compaction and traction benefits.
“Typically, when fields are dry and traction is good, the more tires you add, the less efficient your tractor becomes,” Turner says. “Duals are worse than singles and triples are worse than duals. Farmers should stay away from triples. If that much flotation is needed, then larger radials as duals are more efficient than the smaller ones as triples. When the soil gets too wet, farmers shouldn't be out there [in the field] anyway.”
Turner doesn't stop at picking on triples. He also points to the long lugs on new tires as a potential energy waster. “Unless you're in mud, lugs aren't a good thing. Every time a lug bends, the tractor is using energy that does not add to the operation at hand.” Turner says older tires with worn lugs are more efficient at providing power to the ground and better fuel economy.
But if you have a choice between an old bias ply and a new radial, opt for the radial. “A properly inflated radial is 6 to 8% more efficient than a bias ply tire,” Turner says.