Your average garage door weighs several hundred pounds. Why is it so easy to raise? The motor in most garage door openers is no more than 2 hp. And when the door is disconnected from the opener, your 10 year old daughter can lift it with ease. The reason is the garage door springs — a suspension mechanism of engineered physics that makes lifting your door feel as light as a feather.
The way that suspension system works is as a counterbalance system. The springs provide an assisting force to make lifting easy. There are 2 types of springs that do this, depending on the style of door — extension springs and torsion springs. Here’s how they work.
Torsion spring loaded doors are the most common. Usually, your torsion springs are mounted above the door opening. When you lower the door, the cables at the bottom corners of the door wind the springs up, creating stored energy that will later be used to raise the door. As the door lifts back up, the springs unwind. But a spring only has so many cycles in it — usually between 10,000 to 15,000. Eventually, the spring will become too weak and stretched to work effectively and will need replaced.
Extension springs are attached to cables that connect to the bottom corners of the door. The springs stretch as the door is closed, storing energy in the extended springs as the door lifts.