Abstract: A transmission belt (10) has a contact face (18a) which contacts a pulley when the belt (10) is wound around the pulley. Foreign matter (25) is embedded near the contact face (18a) in the belt (10). The contact face (18a) is worn by the pulley when the belt (10) rotates around the pulley, so that the foreign matter (25) is exposed at the contact face (18a). The foreign matter (25) contacts the pulley to make a warning sound. Due to this, a user of the belt (10) can determine the extent of the wear of the belt (10), and the decrease in the transmissibility of the belt (10) and the pulley.

Abstract: A torsional vibration damper or other vibration damping device with a rubber vibration absorbing element. The rubber element is a peroxide-cured composition comprising 100 parts of ethylene-alpha-olefin elastomer, and 20 to 100 parts of substantially isobutylene or butene polymer having a viscosity average molecular weight greater than about 5000. The polymer may also be a copolymer of isobutylene and isoprene. The addition of the isobutylene polymer to the ethylene-alpha-olefin elastomer composition increases the vibration damping character of the rubber.