In this study, the interactions between the different brake pressure changes and the changes at slip ratio and wheel acceleration which was obtained during hard braking with ABS on wet and slippery rough roads were investigated in frequency domain. The different brake pressure characteristics were achieved by chaging the damping capacity of shock absorber. For this aim, ABS tests were conducted on rough road using hard, medium-hard and soft shock absobers. In experimental study, the wheel speed, the vehicle speed, the brake pressure changes and the effective rolling radius were measured. The ABS control parameters were calculated from measured parameters. Two different frequency response functions (FRF) between the brake pressure and ABS control parameters were found by program written in MATLAB. In FRF results, the slip ratio and wheel acceleration were excited at different frequency and amplitudes by the brake pressure changes. The responses of ABS control parameters against brake pressure changes provided the control performance of ABS to be determined. Therefore, it was observed that the factors determining the control performance with respect to road type and damping capacity changes were the change rate, amplitudes and number of the responses. As a result, the road type changes were determined by these factors; however, the changes at shock absorber damping capacity were determined by the shifting of resonance frequency as well as these factors.
