when braking..I noticed it? I noticed it does the shaking with my regular tires and my chrome rims as well . . . the same spot which is the drivers-side back tire. When taking the tire off the piece that spins round circular was sort of out of wack like the others, meaning it didnt spin in a straight circle it was warped which i think is doing all of the shaking...What would I need to replace to fix this ...simply buy a new rotor?