Advantage Garage Doors February 15 3 min read

Know It All! – Garage Door Springs – Extension Springs

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Additionally to the types of springs covered in the previous two Know It All! posts, Torquemaster and torsion springs, some doors may be counterbalanced using garage door extension springs.

While most garage door extension springs will be oil-tempered, some are made of galvanized steel. Extension springs counterbalance the garage door via a cable pulley system. One end of the spring is affixed to a bracket on the horizontal track, while the other end is connected to the door by a pulley. One end of the cable will be attached to the bottom of the door, while the other end will be connected to the horizontal track using an S-shaped hook.

As its name implies, the spring is stretched (”extended”), upon opening the garage door, counterbalancing its weight.

Variations in Extension Springs

Extension springs have a number of important parameters you should familiarize yourself with. As with other types of springs, the length, inside diameter, and wire thickness are crucial. The initial tension is the amount of force needed to separate the coils on an extension spring. Lastly, the type of ends on your extension springs will dictate how they will be connected to your garage door.

There are three types of ends for extension springs, listed in order of durability.

*Open Looped

*Double Looped


Safety Cables

Safety cables are an extremely important part of the garage door extension spring system. As they are under a great deal of pressure, these springs can severely maim or even kill a bystander when they break. They can cause extensive damage to property stored in the garage as well. A safety cable runs through the length of the extension spring, preventing the pieces from becoming dangerous projectiles upon breaking.

Replacing Extension Springs

When one of the extension springs break, it is advised to replace both as they have the same cycle rating and have typically endured the same amount of wear. Checking the pulleys for wear is also essential, as well as examining the cables for signs of fraying or other damage.

Extension springs tend to have a lower cycle rating than other types, unless you have installed specially manufactured longer life extension springs. The typical rating is 7000-10000 cycles for a standard extension spring, compared to 10000-15000 for torsion springs.

To replace extension springs, your door’s height and weight must be accurately measured. Extension springs are color coded as well, aiding in finding the right spring for your garage door.

We do not recommend installing extension springs, due to the safety hazard they can potentially represent in your home, as well as their diminished life cycle in comparison to torsion springs. If you currently have a broken or otherwise damaged extension spring system, we recommend you opt for conversion to a safer, sturdier torsion spring system.

Feel free to comment or send us a message with your questions!

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