More stringent requirements for reliability of truck wheels and hubs have increased the demand for faster and more realistic testing. The test program described in this paper was designed to obtain sufficient information to define the criteria for the design and construction of a programmable road simulator specifically for truck wheels and hubs. An Instrumented wheel, hub and axle were tested in a normal road environment and on a proving ground. The results, in the form of strains, were compared to those obtained from laboratory Bull Wheel and cornering load tests. From this data and from static tests, actuator sizes, maximum frequency and displacements, number of degrees of freedom, horsepower requirements, rotation speeds and other pertinent road simulator design criteria have been selected.