Tire Bulge problems of the 2006 Dodge Ram 1500

Goodyear wrangler hp p275/60-20 tires. Purchased used 2006 Dodge Ram 1500 quad cab 4x4 with these original equipment tires (32,000 miles). In may 2009 had a tire failure; blowout at low speed following exit from interstate(33,000 mi). Goodyear dealer advised that goodyear would classify the failure as road hazard and would not replace the tire. Purchased 1 new tire of same kind and immediately had balance and unusual wheel hop. Appealed to goodyear who replaced the tire. Replacement tire had similar balance issues. Selected location on vehicle with least impact to drive-ability. During fall 2010 (40000 miles) began to notice left rear vibration as though tire was out-of-round. On Feb 10, 2010 discovered left rear had belt separation and large bulge. Steel belts are extruding out of tread. In process of mounting spare noticed apparent belt and tread separation on spare. Four of six tires have had issues. Am replacing all tires. No more goodyear's, ever!.