Dust cover, part number 42604-413-780 has failed again. Why, seal was replaced about 500 miles ago with a new one, pricey and hard to find, is this seal/dust cover necessary??? Why did it fail??? The damage to the dust cover looks like the rubber stuck to the axle and the rotation of the wheel tore the rubber apart. Suggestions?? There was a thread about this item a year or so ago but I can not find it.