The outside edge, and only the outside edge; not the inside edge, of all 4 tires are wearing out. First set lasted approx 22K. New ste showing outside wear at 16K. have has tires aligned 3 times, rotated every 6K, balanced. Check tire pressure regularly. I know underinflation can lead to premature wear on the edges but I don't believe this is the case. Anybody else experiencing this problem.