Garage Door Cables Are strands of wire twisted together and then bundled and twisted to form cables that are strong enough to lift the garage door. Garage Door cables are the component that actually carry the load of the door when opening and closing. Many things go Into the strength rating for garage door cables. First are the wires themselves typically made of aircraft aluminum or stainless steel to reduce corrosion to the wires. Next are the number of individual wires in each strand and finally the number of strands in each bundle. The heavier the garage door, the stronger the cable should be. Garage door cables have a loop at one end that attaches to the bottom bracket of the garage door and at the opposite end there will be a stop and sometimes a slide stop that attach to the drums(for torsion spring systems). The loops can be simple open loops, loops with spools, or loops with a thimble.
In a torsion spring system the loop of the cable attaches to a stud on the bottom bracket on either side of the garage door. The cable is then run up the height of the garage door and the stop or slide stop if present attaches to the drum. As the door goes up the cable winds itself around the drum and as the door closes the cable unwinds from the drum. The drum is attached to the torsion tube at the top of the garage door opening. In this type of system the torsion spring/s provide the force via the torsion tube through the drums to the cables to open and close the garage door.
In an extension spring system the loop attaches to the stud on the bottom bracket on either side of the garage door and threads up the height of the garage door and through a pulley system that attaches to the extension spring. The cable attaches at the open end back to the garage door track. The other end of the extension spring attaches via a hook to the track support bracket near the ceiling. In this type system the cable running through a series of pulleys and attaching to the extension springs provides the force to open and close the garage door.