The common causes of pulsating car brakes can include the Antibrake System (ABS), a poorly installed wheel or a warped rotor. In fact, pulsating car brakes is a common complaint regarding ABS brakes when the ABS system kicks in. This usually happens when braking on ice, wet roads, or gravel.
Unfortunately, the most common cause of pulsating brakes would be the rotor. The rotor may be warped, but it could also be misaligned. If the wheels were recently installed or have had maintenance work done on them, head back to the auto mechanic and have them double-check to be sure they were installed correctly. If recent work has not been done, the rotor might be warped. This can be caused by sudden braking. Visit a reputable auto mechanic to install a new one if unsure of how to replace it.