Most modern residential garage doors use a torsion spring lift mechanism rather than an extension one. It has fewer components and is regarded to be safer and more dependable. More importantly, it works effectively to enable the proper opening of the unit.
It is set over a shaft which sits above the overhead door and is typically placed in the center. The spring is loaded with energy that matches the weight of the door. This is how the component keeps the unit balanced and securely in place at all times. On each end of the shaft, there is a drum. There is a lift cable attached to each drum. The other end is connected securely to the bottom of the door.
When you push the button of the remote control or that of the wall-mounted console, the opener will start pulling the door up. At this point, the spring will start releasing the energy which it holds. It will be applied to the drums and they will transfer it to the lift cables. This is how the cables help to drive the door up along the tracks.
The torsion spring lift mechanism does most of the work when the garage door is lifted. The role of the opener is significantly smaller. Still, when it has the appropriate amount of horsepower, it can speed up the opening considerably.
Both the spring and the lift cables of the mechanism are under great tension when the door is in closed position and work hard to open it. That is why they break eventually. It is important for these components to be inspected very carefully during maintenance so that they can be fixed or replaced timely if there is a problem.