2002 WELLCO TRAILER Tires Problems

THE PROBLEM OCCURRED ON AN 8X18 ENCLOSED WELLS CARGO MOTORCYCLE TRAILER. I LEFT FREDERICK, MD ON THE MORNING OF 7/29/06 HEADING TO MYRTLE BEACH, SC . WHEN I GOT INTO VA. [APPROX 45 MILES FROM FREDERICK] THE RF TRAILER TIRE BLEW. I PULLED INTO A SHOPPING CENTER PARKING LOT TO CHANGE IT AND NOTICED THAT THE RR TIRE WAS DEVELOPING A BULGE IN THE FIRST TREAD FROM THE OUTSIDE. I CHECKED THE OTHER TIRES AND THEY WERE OK. I REPLACED THESE 2 AND ARRIVED AT MYRTLE BEACH WITH NO FURTHER TIRE PROBLEMS. BECAUSE OF WHAT HAD HAPPENED GOING DOWN ,ON THE WAY BACK HOME ON 8/5/2006 ANY TIME I STOPPED I WOULD INSPECT THE TIRES. WHEN I STOPPED IN WILSON, NC I NOTICED THAT THE LR WAS DEVELOPING THE SAME BULGE IN THE TREAD AS THE OTHER TIRE WHICH DID NOT BLOW. I KEPT AN I ON THE TIRE AND...