bale wire baler parts conveyor systems BALE WIRE Two factors used to determine quality of bale wire are tensile strength and elongation. Good bale wire (black annealed) will have a tensile strength of 69,000 to 75,000 PSI. Elongation is the ability of the wire to stretch before it breaks. A bale wire with good wire elongation would be that of 25 per cent or more. Less expensive bale wire on average has an elongation factor of 15 per cent. It's important to note that baler manufacturers produce balers more powerful than earlier models, so these factors are especially critical now.