They coat new tires in prep for shipping in storage with some funky green stuff. Usually takes a hell of a lot of scrubbing to get it off. Mike has a good post on using a DA w/ brush to get the crud off new tires. I personally just use one of the Mothers Tire Brushes (stiff bristle) and some good degreaser, soap and water and give them a good brushing and rinse. It will take several passes before you get everything off.