THE BRAKES BUILD UP PRESSURE WHEN PUSHED MULTIPLE TIMES CAUSING THE BRAKES TO NOT ENGAGE AND PROPERLY STOP THE VEHICLE. THEY GET SO TIGHT YOU HAVE TO PUT ALL WEIGHT AND FORCE POSSIBLE IN THEM TO STOP. I'VE CALLED MULTIPLE DEALERSHIPS AND EVEN CALLED GM DIRECTLY AND AFTER INVESTIGATION THEY SAY THEY COULD NOT SIMULATE THE ISSUE AND ITS NOT A KNOWN ISSUE. I HAVE FOUND NUMEROUS REPORTS ON THIS AND IT WAS VERY EASY TO FIND AS A KNOWN ISSUE AMONGST GM OWNERS.