What is a drive belt?

On a dryer the belt wraps all the way around the drum and drives it from a small motor pulley, tensioned by an idler pulley. When it snaps, the motor runs and the drum sits still, a distinctive symptom. Belts also glaze and slip before they break, usually because a worn idler is no longer holding proper tension, which is why the belt, idler and rollers are normally replaced together as a kit rather than one at a time.