2003 Ford Taurus 6 cyl Front Wheel Drive Automatic 95000 miles
When I apply the brakes there is a shimmy in the steering wheel. I have had the tires balanced and the rotors replaced and resurfaced with no luck. The strange part is that it doesn't always shimmy. At times when I drive the car it brakes smooth and straight, other times when the brakes are applied lightly it shimmy's quite hard but other times when the brakes are applied a little firmer the seem fine.
what causes this? I'm thinking a proportioning valve but I'm shooting in the dark.