Brake squeal is one of the major issues in the design process of an automotive brake and the development of a robust procedure for a "squeal-free" design is still under investigation. This paper presents an experimental investigation on a beam on disc setup. The experiments allow for the direct measure of the lock-in and lock-out characteristics of such a system for different values of the damping. The analysis shows the qualitative changes in the modal coupling as the value and distribution of damping change. Moreover and the results provide interesting guidelines to control squeal occurrence when adding passive dampers to the brake apparatus. In certain cases, an increasing tendency to the unstable behavior for increasing damping is highlighted.