Lee, I'm not a gambler, but I would put money on your problem being wheel bearing related. A few CEGers replied to this proposed culprit by saying that in their case, they have lotsa miles without wheel bearing problems. Good for them, but that doesn't mean that wheel bearings aren't historically problematic with Contours.
2 ways to test for wheel bearing problems:
1. Jack up the offending corner of the car, remove the wheel, and rotate the hub by hand. Put your hand on the hub while doing this, and you may be able to feel the vibration. You can't blame tires if the wheel is off the ground!
2. Does the noise go away with a slight turn of the steering wheel to one side, and it doesn't go away with a slight turn to the other? This is a classic symptom.
Best of luck finishing your diagnosis.
