I got the decals off my Trek 5200 by steaming them off. The acrylic adhesive on the polyester decal can be softened and then peeled off after the applicaion of heat. Pull the decal off like skinning a rabbit. If you haven't had that pleasure, pull the decal straight "down" so the angle of peeling is 180 degrees. This will put the most stress on the adhesive so the deal comes off and the least amout of stress on the polyester so it doesn't tear as easily.
Don't sand or use solvents.
Don't sand or use solvents.
