My brakes release when applied hard

When this happens, does the brake pedal go down farther or feel like it pushes up, or do you feel the brake pedal "vibrate" or"pulsate"? .................................................................................................................................................... If so, you are describing the ABS anti-lock braking system perfectly which means you are stopping so hard that the car is skidding!!!!!!! The grinding noise is the abs pump and valves working incredible fast. Also, make sure all your tires are a matching set and all worn the same and are all properly inflated. If one tire is worn more than another, or a different brand or size, the abs may activate early.