I've heard from a few people that the aluminum pulleys will wear down over time and become unusable as opposed to steel pulleys. Just wonder if anyone who has been running aluminum pulleys for more than 30-40K miles can comment on how well they have held up. One of my friends has a aluminum idler pulley on his Dakota and it has a groove in it from the belt after 50K miles of use. It's not that bad IMO, but does affect the tension on the belt as it wears down the pulley.