Tire Bubble problems of the 2004 GMC Yukon

The contact owns a 2004 GMC Yukon xl equipped with hankook ventus as tires, size was 305/50r/20xl. While driving approximately 50 mph, the steering wheel began vibrating. The vehicle was taken to the tire shop where the tires were purchased. The technician stated the front passenger side tire had a bubble on the outside and needed to be replaced due to tread separation. The tire was replaced. The contact experienced the failure a second time and was taken to the tire shop. The technicians stated the rear passenger side tire needed to be replaced due to tread separation. The contact stated he did not have the tire replaced because the manufacturer would not assist with the cost and he felt it was a safety defect. The approximate failure mileage was 122,000.