You might not be able to see it, but an accessory drive belt is always both speeding up and slowing down.
Andrew Markel discusses vibration control alternator pulleys, and the differences between the two most common designs available on the market. Sponsored by Litens.
The original equipment belts on late-model vehicles are made of synthetic materials and are far more heat-resistant and wear-resistant than older materials. These innovations mean serpentine belts may last up to 100,000 miles before they need to be replaced. If a belt fails sooner, you need to be a detective and investigate why it failed.