I have a 2003 Toyota Camry 2.4L, about a year ago I had a flat tire on my rear passenger side tire. I replaced the tire with a Michelin Pilot, to match my other tires, I just got the new tires when I replaced that one. I had to replace it because I have the low profile tires, and the dealer said that the side wall was messed up on the flat, which is common. This past August I noticed a ruff sound coming from my back tires, I took them off and inspected them and noticed that the rear passenger tire had knots in it. I took it back to the dealer and they prorated the tire for me. Now the new tire only has 6,000 miles on it and, once again has knots on the tread. What could be causing this? Before I take it back to the dealer I want to have some info on what could be causing this, since I don't think that they will be to eager to say that it is a defective tire again, one time, yes, but two tires on the same side with the same problem, I'm thinking it could be something with my car, or just another bad tire, any suggestions?