Just as the vibration modes of a beam are dependent on its end constraints or boundary conditions, vibration modes of a tire are dependent on its patch and spindle constraints. This dependence is key to understanding the dynamic properties of a tire and is apparent in various analytical and experimental investigations in the literature. Tire Finite Element(FE) Analysis and modal test results are presented here which demonstrate this dependence. Then, the influence of tire modes in tire highway-speed uniformity testing is discussed. Finally, the importance of tire dynamics in suspension dynamics is demonstrated. A comparison is given between modal analysis of a simple suspension with a tire modal model and the same suspension with simple spring rates for the tire.