Dayco POWERBOND OEM Replacement Balancers offer the option of a totally new assembly featuring high grade Spheroidal Graphite (SG) iron castings assembled with new inserted or bonded rubber as used in the original balancer. The Harmonic Balancers rubber diaphragm is among the many components in the assembly that is designed to absord significant torque forces between the hub & accessory drive ring. As the rubber ages it will weaken, allowing small tears in the rubber causing the balancer to fail and stop the vehicle. If your vehicle has done over 100,000km's, Dayco recommends changing the balancer as part of routine maintenance. The tell-tale signs of rubber diaphragm deterioration includes cracking around the edges & across the face, run out in the drive pulley, increased vibrations & rubber degredation.