Bad Brake Vibration
I have a 1999 Mercury Mystique with discs up front, drums in the back. For about the last 500 miles or so, when you apply the brakes (not a panic stop but just to slow down), you get a very bad vibration, especially on the highway at high speeds (pretty scary). The whole car shakes and the pedal pulses. However, at low speeds, sometimes you get it, sometimes you don't. I know what the ABS feels like when it kicks in and this isn't it.
The car has 52K on it. I replaced the rotors at 41K, so they have less than 12K on them. I also pulled them to see if they were warped, but except for a little minor pitting here and there, they appear to be straight with a lot of material left on them. I also pulled the backs and could see no problems. Pads were replaced front and back with a premium brand when I replaced the rotors. They look fine with plenty of wear left on them. Also, I replaced springs, hardware, etc. in the rears at the same time as the pads.
The brake fluid is clean, brakes have been bled; no sponginess in the pedal. The car has a 2.5 V6 auto with air, ABS. No warning light from the ABS system has appeared. New tires last year (balanced and alignement), same size and specs as what was previously on it. I can't believe the rotors are warped after so few miles and that they spin fine with no high spots, but it sure feels like it. Any thoughts?