Tire Sidewall problems of the 2000 Chevrolet Express

The contact owns a 2000 Chevrolet Express. The vehicle has goodyear ultra metric bst radial tires (na). While driving 40 mph, the vehicle began to shake. The dealer stated that one of the tires was defective and refused to replace it for free. Currently, two more tires have become defective. The powertrain and tire size were unknown. The current mileage was 82,738 and failure mileage was 65,000.