I purchased my '13 Passion convertible with Continental set of 165/60R15s in front and 195/50R15s in the rear. They appeared to be the original tires with 41,000 miles on them. Rear tires were down to the wear bars so I replaced them with Hankook Ventus V2 Concept, same exact size. Car always drove/handled as good or better than my 24 year old Miata. Now on a mountain dual carriageway right hand 60 mph bends have caused frightening thumps from the right front wheel.........feels like the tire is rolling off the rim.... The rear tires are soooooooo grabby, but the pre-existing fronts seem to have disappeared........What the heck is going on? Is it merely due to my rear tires having zero miles and the fronts have hardened with 46,000 miles? I do realise that 165/60R15s in front were never matched with 195/50R15s in the rear........when it comes time to replace them it will be with Hankook Ventus V4 175/55R15s.......please help.