Maybe not all Duratracs are created equal. Long time ago when consumer reports was asked if tires sold a discount outlets (like sams club) are inferior they sort of confirmed it to be true:
"....Tire manufacturers make all the tires that go to the car manufacturers and to after-market on the same machines. However, they then quality check 100% of the produced tires, as the manufacture of tires can be hit and miss. The best quality tires usually go to the OE manufacturers, the next grade usually to the tire stores and the 3rd grade usually go to the discount stores."