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What is an Extension Spring?

B. Turner
B. Turner

An extension spring is a tightly-coiled spring mechanism used to operate an overhead door. These springs can be found on many types of coiling doors, including those found in residential garages, automotive shops, and warehouses. On a standard garage door application, the extension spring is positioned along the ceiling. This type of operating system provides an alternative to torsion springs, which fit into the space just above a closed garage door.

Many overhead doors utilize tracks that run vertically from the floor to the top of the door opening, then continue horizontally along the ceiling. In this standard application, installers place a pair of extension springs on the ceiling between the tracks. When the door is closed, these springs are fully extended, and at their highest point of tension. As the door opens, each extension spring contracts, and tension is reduced. The springs are attached to the door using a series of pulleys and cables, which are used to operate the door manually or by remote.


Garage door manufacturers set the initial tension of these springs based on the size and design of the door. By varying the wire size, length, or diameter of the spring, manufacturers can match the extension spring to the door to ensure successful and long-lasting operating. Each end of the spring features a hook or clip that allows the installer to easily fasten it to surrounding components. These hooks may be fixed or stationary depending on door design.

Over time, extension springs may wear down or stretch out, which can lead to difficulty opening or closing the garage door. Because of the high tension contained within an extension spring, these springs should only be installed or repaired by experienced professionals. Novice installers may cause severe injury to themselves or others while attempting to work with these springs. Even in instances where no one is injured, the springs can still cause property damage if handled incorrectly.

Squeaky or noisy springs can be sprayed with lubricant to reduce friction and improve operation. These springs should be inspected regularly to check for signs of damage, including loose or fraying cables. Homeowners should always have both springs replaced at the same time, as one damaged spring is a good indication that the other is reaching the end of its life. In addition, replacing just one spring exposes the other to different forces and stresses than before, which could cause the spring to break.

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