1997 Chevrolet Impala SUSPENSION,TIRES

I PURCHASED A 2007 CHEVROLET IMPALA ON 5-25-07 WITH NO MILEAGE. ON 9-10-09 WE HAD A NAIL IN THE TIRE AND TOOK IT TO BE REPAIRED AT A TIRE SHOP AND THEY RECOMMENDED WE INSTALL 4 NEW TIRES B/C THE INSIDE OF ALL 4 TIRES WAS WORN DOWN TO THE CORDS. WE TOOK THE CAR TO OUR DEALERSHIP AND THEY FOUND THE REAR ALIGNMENT TO BE OUT OF SPECIFICATIONS AND PUT ON 4 NEW TIRES AT THEIR EXPENSE. ON 7-14-10 WE TOOK THE CAR IN FOR AN OIL CHANGE AND ROTATION, THE LOWEST TREAD DEPTH WAS RECORDED AT 8/32. ON 9-14-10 THE CAR WAS TAKEN IN FOR AN OIL CHANGE AND THE LOWEST CAR DEPTH WAS RECORDED AT 6/32. I SPOKE WITH THE SERVICE MANAGER ABOUT THE DRASTIC CHANGE AND TOLD HIM I WAS CONCERNED WE WERE HAVING A REPEAT PROBLEM WITH THE ALIGNMENT AND OUR WARRANTY WAS ABOUT TO GO OUT. THE SVC MANAGER AGREED TO DO A FREE ALIGNMENT AND CHECK FOR THE PROBLEM AGAIN AT MY NEXT OIL CHANGE. I HAVE READ MANY OTHER COMPLAINTS ABOUT THE TIRES AND ALIGNMENT ISSUES SUBMITTED ON NHTSA. THIS SEEMS TO BE A COMMON ISSUE ON THE POLICE CARS AS WELL AND THOSE WERE RECALLED. *TR