High Performance Polyurethane Carbon Timing Belts. Highly dynamic, tough, tear-resistant, durable, and brand new: The optibelt DELTA Chain with carbon cord is the perfect alternative to drives with roller chains. Designed for high torque, it delivers the best performance values even under extreme conditions and high loads. Our innovation studies showed in extensive tests that a performance increase of up to 100% over comparable high performance synchronous rubber belts is possible.