Outside edges of front tires have noticeable wear on 99 Durango 4x2 with 18K miles. Serviced at 7.5k and 15k, tires rotated at both intervals. Alignment seems good. Brought it to dealer and was told that they are checking for possible suspension problems. They also mentioned that they were currently looking at a couple other Durangos for suspension problems. Has this been a recurring problem??