Modeling of friction pad in disc brakes as a distributed parameter system (mass-inherent damping-elasticity) is made in order to show the conditions of stable vibrations, The interface characteristics of the pad/disc assembly beside the negatively sloped friction-velocity relationship are taken into account. The interface characteristics are represented by the effective contact stiffness as well as the friction damping of both pad and disc surfaces. It is shown that continuous modification of the equivalent contact stiffness by wear mechanism or by any other mechanism, is the mean cause of squeal triggering. The analysis has shown that stability can be attained at all possible squeal frequencies of the friction pad by the good selection of its geometrical configuration (thick, wide and short brake pad) and its material loss factor within certain limits. Moreover, it is necessary to choose the appropriate way of pad fixation inside the caliper to give higher modes of vibrations. According to the considered model of longitudinal vibrations, it is found that stability of motion is independent of the value of coefficient of friction whereas it depends upon its negative slope.