Try using some degreaser to break up the grease and grim and some dirt. Also use some windex to break up even more. The windex has a gassy substance so it works like a very very very weak walmart type acid on dirt and grime. After you've done that wipe it down good and then clean with soap and water and rinse. If that don't help, go buy you some paint of your color and enjoy your new color rims ;-)