Depends on what bearings we are talking about. My Avid ceramic bearings, I toss in the blue vibrating thing with citrus cleaner for about 20 minutes, then rinse with water. Pat dry then lightly dry with a heat gun. Do not spin them until you put bearing oil in them. The $1 bearings by Avid, just toss them and put in new bearings. Pretty much the $1 Avid bearings are really good. They come packed with grease and will last a long time without maintenance, when they go bad it is generally because of smacking the walls.