One in five vehicles needs a belt

Neoprene Belt Wear vs. EPDM Belt Wear

Since the late 1990s, automotive manufacturers have phased out Neoprene serpentine belts and are now installing ethylene propylene diene monomer (EPDM) belts on new models.

While it's hard to tell neoprene and EPDM belts apart visually, EPDM belts far outlast and outperform their predecessors. Neoprene belts have a life expectancy of 50-60K miles, and as they wear out, cracks and chunk-outs will occur. EPDM belts rarely show these symptoms, even at very high mileage.

Belt wear after 100,000 miles
Neoprene belts vs. EPDM belts Visual Wear - Gates

As EPDM belts age, they gradually lose rubber material similar to the way a vehicle’s tires wear out. Over a period of 100,000 miles, a belt can lose up to 10% of its rib material. While this may not seem like a lot, the consequences can be significant.

Common Belt Wear Problems

When EPDM serpentine belts lose material in the valleys of the ribs, the space between the ribs widens without the ribs getting shorter. As more material is lost, the pulleys ride deeper into the belt valleys resulting in slip, noise, and hydroplaning.

With sufficient material loss, the pulley ribs “bottom out” in the valleys and ride on the belt cord. This reduces the surface contact on the valley sides where the traction is generated. Wear also increases the effective belt length, lowering the tension in the system, which also reduces traction.

Belt wear problems that reduce performance of the Accessory Belt Drive System (ABDS) include:

  • BELT SLIP: Like a tire, a worn belt can lose traction, or slip, on the pulleys, particularly in high-load or wet conditions. Slip can cause belt and pulley temperatures to rise by up to 50%, leading to early accessory bearing failure.
  • HYDROPLANING: When water cannot be effectively channeled away between a worn belt and the pulleys, the belt can hydroplane on a film of water, resulting in loss of power transmission to the accessories. This can often trigger a vehicle’s "check engine" or “alternator charging” warning lights.
  • ELONGATION: Material loss can cause a change in the effective length of the belt, which can move the tensioner beyond its take-up range. This will reduce overall system tension, lowering accessory performance.
  • MISALIGNMENT: Misalignment wear may be an indication that the internal components of the tensioner have failed. Material loss and subsequent changes to the effective length of belts can also cause belt slip, resulting in noise, vibration, and high heat, which can damage accessory bearings and cause accessories to fail.

EPDM Belt Wear Symptoms

If your serpentine belt exhibits one or more of the symptoms depicted, it needs to be replaced.

Belt Wear abrasions, cracking, glazing, piling

Gates Belt Wear Gauge for Serpentine and EDPM Belts Read more about the free PIC Gauge app for your smartphone. Two Guys Garage Garage on Belt Wear Gates Tech Tips for Serpentine Belt Wear and Diagnosis