A vehicle braking system is used to provide acceptable drivability of the vehicle and ensure safety in different emergency situations that the vehicle may encounter. The braking system is used also as an integrated sub-system in many other important vehicle driving systems such as traction control, adaptive cruise control, accident avoidance and other vehicle systems in which the braking system plays an important role. This paper is dedicated to provide an accurate and at the same time simple enough hydro-mechanical braking system mathematical model that takes brake pad wear impact on the system pressure dynamics into consideration. A wear simulation procedure based on the concept of Archard's wear law is used and integrated in the nonlinear braking system model with flow compressibility taken into consideration. The presented model simulation results and the experimental tests results show good agreement and validate the confidence in the proposed model. Also, a reduced order model of the full nonlinear one is presented. Both the full nonlinear model and the reduced order model show that increasing in the brake pad wear level increases the pressure spikes dynamics at the contact surface between brake pad and rotor disc and hence could leads to brake squeal and shortens the braking pad service life.