FABRIC AND STEEL
Because tires have to carry heavy loads, steel and fabric cords are used in the construction to reinforce the rubber compound and provide strength. Among those materials suitable for the tire application: cotton, rayon, polyester, steel, fiberglass, and aramid.
Fabric cord quality is based on its strength, stretch, shrinkage, and elasticity. The yarn used is first twisted, and then two or more spools of yarn are twisted into a cord. Before shipping the cord to the tire factory, the manufacturer pre-treats the cord and applies an adhesive to promote good bonding with the rubber. The temperature, humidity, and tension control are critical before the fabric cords are calendered with rubber compound. For this reason, fabric cord is kept in a temperature-and-humidity-controlled room once it arrives at the factory.
Steel wire cord quality is based on tensile strength, elongation, and stiffness. It is manufactured from steel rod with high carbon content; and while the steel wires used have different configurations, all are brass-coated strands twisted together into cords. If the wire is used in a multi-ply tire rather than a belted tire, the fatigue performance will be important. If used in belted tires, then stiffness is of primary concern. Since the steel wire is brass coated, storage conditions are important to maintain the steel wire to rubber bonding properties. Therefore, the steel wires are also kept in a temperature and humidity controlled room once they arrive at the factory.