I purchased 4 new kumho solus kr21 p215/60r16 tires on july 18, 2013, from tiresouth in atlanta, ga. when i tried to register them on the company's website, i found that 2 of them do not have date codes (only 8 characters after ?dot? instead of 12). does this mean that the tires are inauthentic or defective? i have attempted to contact kumho multiple times, but have not received a response. *tr