Rear Suspension problems of the 2003 BMW X5

Premature wear of rear tires: the factory set angle of camber leads to severe cupping of the rear tires on a 2003 BMW X5 4. 4 after 30000 miles, cord is showing on the inside of the tire. (bridgestone turanza er30(tz) 285-45r19 107v). Dealer said this is normal wear. In addition, the dealer said the vehicle is setup with high negative camber because it is meant to be driven at 100 mph. The rest of the tread is normal, the vehicle has been driven conservatively, and the tire pressure is checked often. Repair includes replacing the rear tires and a 4 wheel alignment. ($800).