An experimental setup is installed to simulate the rotor-to-stator rub of the rotor system. A special structure of stator is designed that can simulate the condition of the full rub. The vibration waveforms, spectra, orbits and Poincare's maps are used to analyze nonlinear responses and bifurcation characteristics of the system when the rub-impact occurs. Experiments with different conditions, including one and two rotor with single- and multi-disks, are performed. Very rich forms of periodic and chaotic vibrations were observed. The experiments show that the system motion generally contains the multiple harmonic components such as 2X, 3X, etc. and the 1/2 fractional harmonic components such as 1/2X, 3/2X, etc. Under some special conditions, the 1/3 fractional harmonic components such as 1/3X, 2/3X, etc. can be observed as well.