The lifting muscle of your overhead door. This tightly wound spring is twisted to load up force. When the overhead door goes up, the spring unwinds which helps lift the weight of the door. Overhead doors are very heavy and without torsion springs, neither you nor the garage door opener could lift the door. Torsion springs are crucial to you overhead door system working correctly. Some larger overhead doors need more than one torsion spring. Because of the force these springs are under, extreme caution needs to be taken when working on loaded torsion springs.