About 2 years ago I had 4 Dunlop Conquest Touring tires installed on my 2015 Passat. About 5 months ago, less than 15,000 miles we noticed a groaning sound coming from the passenger side rear. I had all 4 tires rotated and now the noise is coming from the passenger side front. This was more annoying than having the groaning noise come from the rear so we had them rotated back again. The "dealer" said it was due to cupping and that's common with Dunlop. He offered to rotate the again to the front and I didn't want that. I want to have the tires replaced but he said the 24 month Road Hazard warranty has passed. He offered to sell me 2 rear tires for a total of $450 which I politely declined. Shouldn't this "cupping" be considered a defect?