Over the past two decades, Dayco® has maintained that serpentine belts should be replaced when an inspection revealed 4 cracks per inch, chunking, rib glazing, backside wear or splitting. Using these criteria, identifying worn serpentine belts was a straightforward process. The belts in this time frame were made from Neoprene compound and were expected to last approximately 50,000 to 80,000 miles.
Today’s belts are now made with an EPDM extended-life rubber compound. These EPDM constructed belts wear completely different than Neoprene, and can last up to 100,000 miles.
All serpentine belts need to be closely inspected to identify any and all wear. These belts are asked to perform in some of the most hostile environments because of high heat, contaminates and debris. Regular inspection of all drive belts and accessories should be mandatory once the vehicle passes 75,000 miles. Vehicles today have more accessories being driven by a single belt then in years past. Remember, if wear is ignored and the belt breaks, the vehicle comes to a dead stop!
Vehicle accessory drives have changed dramatically over the past 20 years. In the past, a vehicles had 2 or 3 belts running a few accessories. Today a single belt is required to run more accessories then ever before. Today, aggressive components (water pump) are being driven by the back side of the belt. This along with high heat and high RPM engines demandstate-of-the-art belt technology.
Also, replacement belts are installed on vehicles with over 80K miles of service and they are far from perfect. Replacement belt typically have to contend with slight misalignments, contaminated and worn components.
The images below show the evolution of belts drives. The belt drive on the left is from 1985 and the belt drive on the right represents todays belts drives - running far more accessories.