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Tire nonuniformities are a major source of vibration problems in vehicles. There is considerable disagreement on which tire uniformity parameters are important to vehicle noise and vibration problems, and on how these uniformity parameters should be measured. This paper is concerned primarily with the effects of the nonuniformities of the tire structure which cause contact patch force variations as the tire is rolled in a straight line at constant axle height. Experimental results showing the effects of mean radial load and roll size on these structural, or static, nonuniformities are presented which indicate that these force variations should be measured on a large roll at rated load. Mathematical analyses of certain vehicle vibrations show that radial and lateral force variation are important uniformity parameters. The amplitude of the first harmonic of these force variations contributes to vehicle shake.

The primary forces and moments which affect the directional control properties of wheeled vehicles are those between the road and the rolling tire. These forces and moments are nonlinear functions of a large number of parameters including slip angle, camber angle, vertical load, tire-road friction coefficient, and traction forces, among others. A new apparatus particularly suited to the measurement of the steady state tire properties most significant in handling studies is described. The forces and moments of interest are defined and typical results fora7.60-15 tire are presented to illustrate the effects of slip angle, camber angle, vertical load, inflation pressure, and wheel torque on lateral force and aligning torque.