The springs attached to each side of a garage door tend to loosen over time. With the right amount of spring tension, the door will open and shut easily. If the spring has too much, or not enough, tension, the door will not work properly. Before swapping in a tighter spring, try and change the tension of your existing spring.
Locate the springs on your garage door. Swing-up doors, which you pull open from a bottom handle, have a spring on each side.
Close the garage door. Remove one spring from the bracket where it is connected. The bracket is drilled into the garage door, and has several holes.
Place the hook end of the loose spring in next hole down. For example, if the spring was in the third hole from the top of the bracket, place it in the fourth. Do the same with the spring on the other side of the garage door.
Open the garage door to check the tension. If it needs more tension, close the garage door and pull the spring down another hole from the top of the bracket. Repeat on the other side.
Test the garage door to make sure that the tension of the spring isn't too tight. If the door is hard to open, and slams shut, readjust the spring by placing it one hole higher on the bracket.
Change out the spring if it is extremely rusty and you are unable to manoeuvre it into a different hole on the bracket.