Tire Valve problems of the 2001 Chevrolet Silverado 1500

The contact owns a 2001 Chevrolet Silverado 1500. While driving 65 mph the contact stated that he felt a vibration, drove the vehicle onto the side of the road and noticed that the drivers side front tires were flat. He purchased four tires to replace the original tires and two of the tires have failed. The tires are yokohama geolander h/t size p265/75r16. He changed the tires to his spare and drove his vehicle home. The dealer nor the manufacturer were called. The failure mileage was 98,000. Updated 12/10/10. The consumer stated all of the valve stems were cracked. The valve stems and tires were replaced. The consumer stated the valve stems were the problem, not the tires. Updated 12/17/jb.