During friction it is well known that the real contact area is much lower to the theoretical one and that it evolves constantly during braking. It influences drastically the system’s performance. Conversely the system behavior modifies the loading conditions and consequently the contact surface area. This interaction between scales is well-known for the problematic of vibrations induced by friction but also for the thermomechanical behavior. Indeed, it is necessary to develop models combining a fine description of the contact interface and a model of the whole brake system. This is the aim of the present work.A multiscale strategy is propose to integrate the microscopic behavior of the interface in a macroscopic numerical model. Semi-analytical resolution is done on patches at the contact scale while FEM solution with contact parameters embedded the solution at the microscale is used. Asperities and plateaus are considered at the contact interface. FFT techniques are used to accelerate the resolution at the micro-scale. As an example the multiscale model is applied into a complex value analysis used to identify modal coupling in NVH simulations. With this model the interaction between non uniform surface and system dynamic behavior is clearly shown. The contact surface variations clearly affect the modal coupling and therefore noise propensity.