HARD BRAKE PEDAL, INCREASED EFFORT IS NEEDED TO DEPRESS BRAKE PEDAL. MOST COMMONLY AT SPEEDS <35 MPH. OFTEN VEHICLE DOES NOT WANT TO STOP. VEHICLE WAS IN MODERATE MORNING RUSH HOUR TRAFFIC. VEHICLE IN FRONT STOPPED QUICKLY FROM 40 MPH. TRIED PRESSING BRAKE PEDAL ON 2015 TAHOE TO STOP, PEDAL WAS EXTREMELY HARD AND VEHICLE WOULD NOT STOP.