2009 VOLVO C30 Tires Problems

RECENTLY I HAVE BEEN EXPERIENCING INTERMITTENT VIBRATIONS WHILE DRIVING. I HAD THE CAR INSPECTED AT AN INDEPENDENT TIRE SHOP WHO FOUND TWO OUT OF FOUR TIRES (ONE FRONT, ONE REAR) WERE OUT-OF-ROUND BECAUSE OF TREAD SEPARATION OR BELT SLIPPING. I BEGAN TO SUSPECT THAT THIS WAS RELATED TO VIBRATIONS THAT I EXPERIENCED EARLY AFTER BUYING THE CAR USED WITH NEW CONTINENTAL DWS TIRES INSTALLED, FROM A VOLVO DEALER, JUST OVER TWO YEARS AGO. THEN I HAD ASSUMED THAT THE PROBLEM WAS A SLIGHT IMBALANCE OR POOR WHEEL MOUNTING. I HAD THE CAR INSPECTED AT A CONTINENTAL TIRE DEALER TO INITIATE A WARRANTY CLAIM, BECAUSE THE TIRES WERE POSSIBLY UNSAFE TO USE AFTER 2 YEARS AND 18000 MILES (WELL WITHIN THE 6 YEAR WORKMANSHIP, AND 50000 MILE TREADWEAR WARRANTY). THEY FOUND UNEVEN CAMBER WEAR AND CUPPING, BUT NO TREAD SEPARATION, AND THE CARS SUSPENSION AND ALIGNMENT CHECKED OUT. CONTINENTAL REFUSED TO...