Factors influencing vehicle ride discomfort are analyzed to separate those related to tires, rims, vehicles and other sources. Ride vibration data is measured with an on-board accelerometer package in 6 component directions along each axis. Raw data is presented as vertical first harmonic accelerations, and is transformed into quantitative “Ride Discomfort” numbers using an empirical model developed by NASA(1)*. The results indicate each factor's quantitative contribution to ride discomfort.Specially selected tires and rims are used on two vehicles in designed experiments. The test programs have been designed to define the net effects of known and unknown sources of vehicle vibrations. Known tire effects include measured variations in radial force and balance, Other known effects include rim runout, wheel stud hole, and axle centering. Road effects, mounting effects, speed effects, and intrinsic vehicle vibrations are considered part of the unknown sources of ride discomfort in this study.Ride discomfort numbers are compared against subjective data gathered by a juried panel. Results are indicated as both a ride quality number and as a test set rejection parameter. The relation of a combination of known factors into subjective feelings of ride quality is discussed. An explanation is proposed that defines previously ambiguous results in terms of quantifiable sources of vehicle ride discomfort.