The contact owns a 2012 Toyota Sienna equipped with Michelin Tires, Tire Line: Cross Climate 2, Tire Size: 235/60/R17, DOT Number: (N/A). The contact stated sidewalls on all four tires were expanding, causing the tires to bubble and bulge outwardly. The dealer was not contacted. The contact informed the tire shop where tires were purchased of the failures, and two tires were replaced. The contact was unsure what two tires were replaced. The manufacturer was made aware of the failure. The vehicle failure mileage was approximately 152,000 and the tire failure mileage was approximately 1,000. The VIN was not available.