Tire cavity noise refers to the vehicle noise due to the excitation of the acoustic modes of a tire air cavity. Although two lowest acoustic modes are found to be sufficient to characterize the cavity dynamics, the dynamical response of these two modes is complicated by two major factors. First, the tire cavity geometry is affected by the static load applied to the tire due to vehicle weight. Second, the excitation force from the tire-road contact changes position as the tire rotates. In this paper, we first develop dynamic equations for the lowest cavity modes of a rotating tire under the static load. Based on the model, we obtain the forces transmitted to the wheel from the tire resulting from the random contact force between the tire and the road surface. The transmitted forces along the fore/aft direction and the vertical direction show two peaks at frequencies that are dependent both on the tire static load and on the vehicle speed. We also analyze the dynamic spectra of the cavity air pressure. Our results show the presence of dominant peaks in the noise spectra. We further report experimental data on spindle responses and the dynamic pressure recorded by a sensor inside a tire. The results are in satisfactory agreement with the model prediction. Our work thus provides a basic understanding for the interaction of tire cavity excitation and a tire/wheel assembly which is critical to develop strategies of mitigating the tire cavity noise in the early stage of tire/wheel design.