Test procedure for the quantification of rolling tire belt vibrations

The ride comfort on uneven roads is affected by vibrations of the tire which contribute to the audible noise inside the car. For any efficient development process, objective testing is essential to obtain a physical understanding of the vibrational behavior. The results of vehicle road testing show that tire modes have an influence on both the accelerations of the axles and on the interior sound pressure. Changes in tire design result in changes of frequency and damping of the belt modes. Indoor testing was carried out with a measuring hub, while the tire was running on a cleated drum. Concerning the vertical forces, the vibrational behavior of the tire can be described by the enveloping process, measured at very low speeds, and the transfer behavior of the tire, defined by a transfer function. Based on this model, a test procedure is derived which allows the measurement of frequency and damping of the first vertical belt mode and of the torsional belt mode. The influence of the inflation pressure and of the tread compound's physical properties is discussed. Measurements on different test stands show, that belt vibrations can be influenced by insufficient stiffness of the test stand.