El Toro

I have a 2005 LS 430 with 20 inch wheels on 245/35/20 Toyo Proxes 4 tires. The car is lowered on Tanabe NF springs and I have spacers to help clear the brakes. I have had no problems from the car or set-up in 20K miles. Recently I have been getting a little vibration while driving and braking. I also have a sound while driving and braking that is very odd to me. I can hear the sound with the windows down or up as long as the radio is off. It sounds almost as if a piece of metal (almost like a giant washer) is loose or rubbing slightly. When I took it to my mechanic, he said that due to the fact that the brakes have several metal parts the sound is normal. He told me the brakes are fine. He feels like the wheel/tire/spring set-up simply magnifies the sound, especially with the open space I have with the wheels and the low profile tires. I disagree, especially since I can hear the sound inside the car with the windows up and the radio off. A friend of mine believes this will go away after the brakes are serviced. What do you think?