2002 Ford Taurus Unusual Tire Wear Pattern and Noise

We have taken the car to several mechanics. One told us it was the front struts and said they needed to be replaced. Another dispelled the strut theory, telling us our wheel rims were bent, causing the uneven wear pattern (wavy) on the tires, and saying the thumping noise was due to the uneven/wavy tire tread.

Recently, we bought a used set of rims hoping this would remedy the problem. The rims came mounted with used tires. We examined the tires for wear before purchasing the set, and found no unusual wear pattern on the tires. We thought this indicated that the rims were in good shape. Unfortunately, after replacing the tires and rims with the used set we still hear the thumping noise, and still feel vibration in the steering wheel (all though it might be slightly less than with the original set of tires and rims).