A few months ago I decided to investigate the vibration that I was experiencing in the front end of my 2002 IS300. While travelling at highway speeds there was a very subtle, yet annoying, vibration of the steering wheel. When the brakes were applied the problem seemed to get much worse. So I was thinking about problems related to: my tires, my wheels, my brake system, my steering system. To systematically work through this problem, I first took off my winter tires/wheels and replaced them with my summer tires/wheels (this set was balanced by the dealer). No resolution of the problem. Next I decided to replace all 4 of my rotors and install new pads. I chose drilled slotted Brembo rotors with Axxis pads. The problem resolved somewhat. The vibration was not noted while braking but was still present while travelling at highway speeds. After a couple months with the new brake set up, the problem gradually became worse to the point where the steering wheel shimmies whenever the brakes are applied. PLEASE HELP!!!! Does this sound like the new rotors are warped (I do not brake any different than the average driver) or is something else going on. Could it be a suspension problem, a steering system problem, some other problem with the brake system? I am at a loss. Any input would be greatly appreciated. Also, besides the normal causes of warped rotors (ie inappropriate heating/cooling cycles) are there any other conditions that would predispose the rotors to warpage?