Your lawn mower belt will be worn down through heat, tension and load over time. This means you may need to replace mower belts every four to five years to keep your machine running smoothly. This can help prevent greater damage to the drive or a full breakdown of your lawn mower. Cracked belts, noisy alternators, squealing on the fan or power steering drives and a worn out battery may all be signs you need to purchase a mower belt replacement for your walk-behind. Make sure you periodically tighten any loose belts as well to reduce the friction on the belt which can increase wear. If you begin to experience drive loss, order a lawn mower belt replacement right away.