Nonlinear self-excited systems in vehicle dynamics are discussed using the examples of squealing automotive disk brakes and the stability behavior of a railway wheelset. Both systems show self-excited vibrations for specific operation states. The self-excited vibra- tions are due to friction forces between pad and disk in the case of the automotive disk and due to contact forces in the case of the railway wheelset respectively. The analysis of the nonlinear equations of motion shows that the trivial solution looses stability either through a sub- or through a supercritical Hopf bifurcation depending on the system’s parameters. In the case of a subcritical Hopf bifurcation two stable solutions coexist and the initial conditions determine which solution emerges. The properties of the nonlinear systems such as critical velocities, limit cycle amplitudes and attractors of coexisting so- lutions are calculated using center manifold reduction and normal form theory.