Actually that's what happened to the Dunlop's. They are flat in the center, pretty much were that way when I bought the bike but I've put 2k miles on it already since May 6th, so now there really bad. Actually that's another question. The front is not that bad but I heard that if you switch brands you are suppose to replace both at the same time because of the curve of the tires, or they will wear faster, is that true?