In the present paper, the dynamics of a nonsmooth friction oscillator under self and external excitation is investigated. The rich bifurcational behaviour predicted by numerical simulations is compared to experimental results. In order to predict the period and amplitude of the friction induced vibrations, the friction force can be modeled by means of friction characteristics. A more detailed look at the nonsmooth transition points of the trajectories shows that an extension of the friction model is necessary. For that aim, a bristle model, a friction contact with tangential stiffness and damping and a stochastic friction model are investigated.