Is your overhead door tall? Is it wide? Does it weigh a lot? Knowing such details will enable you to get the right garage door springs. These are variables which actually make the difference among several kinds of spring systems. In other words, springs are picked by taking into consideration the properties of the door since their job is to lift it. They must actually have equal amount of power with that of the door in order to manage to pull it open.
So, this is how springs are differentiated and why there are several types to cover the needs of different doors. One wouldn't choose the same springs for a door weighing 300 pounds and a door weighing 500 pounds. The height and width of the door are also important since they will determine the number of coils, and thus the length of the spring.
The special properties of springs
Some overhead door springs will manage to carry the weight of average size doors and different springs will be needed for larger and hence heavier doors. All springs have tremendous power since they tend to store their tension as they are extended and release it when they are contracted. Take, for example, a tiny spring used in other applications. If you press it with your finger, you will discover that it will jump back up when you remove your finger. This is similar to what happens to springs used for garage doors but their power is far greater. The way they are manufactured, the inside diameter and the wire size, which is actually the thickness of the coils, will determine their power.
If you observe how extension garage door springs work, you will have a clear picture of their power. You will also notice that their behavior is similar to the little spring you used for your experiment. The springs will stretch when the door is closed, and contract when the door is open. Their power is tremendous and that's why if you hold springs – whether extension or torsion springs – in your hands, you will notice that most of them cannot be compressed or stretched out easily manually except in some occasions when the springs are gapped.
The coils of springs are particularly strong and their size will determine their power. Some, like the oil tempered garage door springs, are actually made by heating, cooling and reheating the wires so that they can withstand heavy duty doors and temperature fluctuations. So, they won't break easily. Such differentiations must be examined since they will make a difference to the movement of each door.