2008 FORD E-450 Tires Problems

PURCHASED THIS MOTOR-HOME NEW IN 2009. DROVE THE MOTOR-HOME 4 YEARS APPROXIMATELY 25,000 MILES WITH NO PROBLEMS. IN MAY OF 2013, I PURCHASED 6 DELTA ESSENTIAL TIRES ( LT225/75R16 ) TO REPLACE THE OLD TIRES THAT WOULD NOT PASS STATE INSPECTION DUE TO CRACKS IN THE SIDE WALLS. THEN WE TOOK A 7500 MILE TRIP ACROSS THE COUNTRY AND BACK WITHOUT INCIDENT. WHEN WE RETURNED HOME UPON ROUTINE INSPECTION OF MY TIRES I FOUND A BUBBLE ON THE INSIDE SIDEWALL OF A REAR PASSENGER INSIDE DUAL TIRE. THE TIRE DEALER REPLACED THAT TIRE AT NO COST. ABOUT TWO MONTH LATER 10/09/2013, WE LEFT ON A TRIP TO DISNEY IN FLORIDA. ON 10/10/2013 WHILE ON I-95 SOUTH BOUND NEAR MIDWAY, GA. THE DRIVER'S SIDE OUTSIDE REAR DUAL TREAD SEPARATED AND THE TIRE BLEW OUT RESULTING IN DAMAGE TO 2 COMPARTMENTS ON THE DRIVERS SIDE. WE HAD THE TIRE REPLACED BY ROADSIDE...

2008 FORD E450, GULFSTREAM CLASS "C" MOTOR HOME. NO ACCIDENT. OBSERVED SEVERE CRACKING IN ALL TIRES, DRYROT. LATER QUESTION TO ID WHICH TIRE, LISTED RF. IT IS ALL 6 TIRES ON GROUND AND SPARE. 7 TOTAL. TOOK IN TO DEALER THIS DATE. THE CONTACTED MFG. MFG OK'ED REPLACEMENT HOWEVER REQUIRES 20% PAYMENT. *TR