Had a question per the I Rotors, which I've had for a couple of months now. I don't know the technical term, but after washing you'll notice a rust color residue left behind after drying. That all goes away after one quick lap around the block, but the dis color is left behind from the areas that the pads don't touch. Someone please school me on this, and what you have done to clean it up. Could it be the material of the rotor itself, or does this happen on all?