Replacing torsion springs is done with the door closed. You start by carefully unloading all of the springs (most standard-size doors have two; any broken spring will already be unloaded), using the winding bars. Then, you unbolt the springs from the central rod bracket, disconnect the cables from the pulleys, and loosen the pulleys and slide them off of the rod. Next, you swap out the springs, reinstall the pulleys and cables, and secure the inside ends of the springs to the central bracket. Finally, you wind up both springs (securing them with two setscrew bolts on the winding cones) and test the door for proper spring tension. Often, springs need an extra quarter-turn or two to get the door balance just right.
Our team of friendly, knowledgeable technicians have the industries best experience replacing broken springs on garage doors. Replacing a garage door spring can be very dangerous, and we highly encourage you to contact us to handle this repair today! If you have a high cycle application, our garage service team may be able to provide extended use high cycle springs. http://youtu.be/Z_eZc-kh40c