Some equipment has multiple V belts. So when one of them becomes worn or breaks, it’s understandably tempting to replace just that one. But it’s important to replace all of them at once.
A machine that uses multiple belts is, by definition, a complex piece of machinery. It is trying to balance different tensions, forces and vibrations which impact different parts of the system. V belts stretch and slip over time. If belts wear unevenly, or one wears out a long time before others, it may be because the tension needs to be adjusted. The other belts in the machinery may be unevenly worn or just about ready to snap too.
So if one V belt is worn or breaks, it may mean that it was simply slightly weaker than the others, or that the system itself is out of balance. In either case, one new belt can “unbalance” a well-worn, functioning system.
This is why you should change all of the V belts at once. Replace them with the best quality belts you can afford. After running your equipment with the new belts in place for a day or two, re-check the tension and adjust it if necessary. Check the equipment again in a week or so to make sure everything is running smoothly and under the correct tension.
Some V belts can last years. If you can’t remember the last time you changed all of the V belts in your system and one breaks, it’s probably safe to say that it’s time to change them all.