Construction vehicles work in a variety of service conditions exposing the tires to loose soft wet clay and mud, paved roads, gravel and to broken concrete, glass and debris at demolition sites. These conditions result in rapid wearing of the treads for such tires.
A particularly difficult application for the tire is when mounted on skid steer vehicles. These vehicles provide turning capability by braking or locking one side of the vehicle's tires while driving the opposite side of the vehicle tires, thus the name skid steer. The tires actually skid to perform a turning maneuver over the terrain conditions stated above. Rapid wearing of tread results as a direct result of this scuffing action. The prior art tread pattern 10 shown in FIG. 1 and as taught in U.S. Pat. No. 4,481,993 is particularly prone to this rapid wearing.
At the leading edge 5 of the lugs 6,8 at the location of the intersection 3 of the inclined shoulder portion 2 and the lateral portion 4 this wear induced by turning is most apparent. The tread 10 is supported by the lateral portions 4 of lugs 6 and 8 when turning right or left and as the tire turns and rotates the maximum resistance to the tuning moment M as illustrated occurs at locations 3. On hard paved surfaces this location abrades rapidly. In broken debris and concrete the location 3 can be chipped and chunked away.
A second phenomenon detrimental to good tire performance results in the unsupported nature of the vehicle load as the tire groove 7 enters the footprint. As can be readily seen, the unsupported region is very large and shifts from left to right as the tire 10 rotates. This results in increased vibration and a non-uniform loading of the underlying tire carcass which in turn transmits these vibrations through the wheel back to the vehicle and the operator.
The resultant transmission of this vibration is bad under straight line driving but becomes worse under rapid turning maneuvers. The operator can actually transmit steering inputs, which can cause the tire carcass to be twisted, and contorted resulting in a vibration transmission commonly referred to as "tire hop." Those skilled in the art have attempted solutions of stiffening and shortening the tire sidewalls which can lessen these vibrations. This solution, however, requires the vehicle owner to replace all his rims and accept a tire with less air damping volume resulting in a stiffer less comfortable overall ride. Due to the stiffer carcass structure an even more rapid wearing of the tread lugs is expected when such a design is employed.
The tire of the present invention provides a tread pattern specifically designed to improve treadwear, reduce vibration and minimize the phenomena of "tire hopping."