Springs are used on commercial overhead doors in several configurations. One configuration that is common is the rollup doors in self-storage facilities. These springs are torsional–that is, they twist and untwist to help raise and lower rollup doors. Eventually, the springs snap due to fatigue stress, and must be replaced for the door to operate. A door that is extremely hard to open, and when opened falls loosely over the top bar rather than coiling tightly around it, is a door with a broken spring. One strong person can replace a smaller, one-spring door in under two hours; larger doors will require two strong people.
Set Up and Remove Broken Spring - Raise the door and put the tools, parts and ladder inside. Use the toolbox to hold the door open enough for light and egress. Lightly file the right end (when facing the door from inside) of the roller shaft all around it to remove rust and any burrs. Pull the cotter pin next to the bearing. Sweep accumulated dust and dirt off the door. Lightly lubricate the right end of the roller shaft and the shaft bearing.
Remove the sheet-metal screws, holding the door top to the roller disks. Handle the door with leather gloves to avoid cuts.
Remove nuts from the screws that attach the left bracket to the wall (on the left end of the roller bar). Using snap-lock pliers, hold the head of each of the bolts that hold the left bracket to the top of the door track. Use a socket wrench to remove the nuts and washers. Leave one of the bolts in place until you are ready to lower the roller bar assembly.
Position the ladder just left of the center of the roller bar, with the hammer atop the ladder. Hold the roller bar up, pull out the remaining bracket bolt, and pull the roller bar left. If necessary, gently tap the right bracket as you pull the bar through the right shaft bearing. Keep the bar horizontal. When the roller bar is free of the bearing, lower it carefully to the floor.
Remove the cotter pin from the left end of the shaft, and slide the left bracket off the end, noting its orientation on the roller bar. Lightly file rust and burrs from the bar, and lightly oil the bar. Match the replacement spring against the broken spring to be sure the coil goes the same way; you will put the other replacement spring, with opposite coiling, on the other end. Use a socket wrench and snap-lock pliers to remove bolts and nuts from both ends of the broken spring.
Attach New Springs and Remount Door - Slide the new left spring and the left bracket onto the roller bar, making sure the bracket is oriented the same way it was when you took it off. Attach the spring to the bracket and roller disk. Replace the left cotter pin. Slide the new right spring onto the other end of the roller bar and attach it to the roller disk with the same size bolt assembly (bolt, nut, washer, and lock washer) you used on the left spring. Attach a bolt assembly to the other end of the right spring (but not, later, to the bracket); the spring is now an installed spare on the roller bar assembly.
Raise the roller bar assembly and slide its right end into the right shaft bearing. Use the hammer to tap lightly on the bracket if necessary. Push one of the bolts through the left bracket into the track (backwards if necessary) to hold the assembly in place. Replace the other bracket bolts, tightening the nuts loosely, then fix the first bolt and tighten all nuts and bolts snugly. Replace the right cotter pin.
Place the socket wrench atop the ladder, and, wearing gloves, use a roller disk to put two turns on the roller bar, in the direction as if the door were going shut. Wedge a gloved hand, gripping the roller disk, between the disk and the door to hold it while you use your other hand to replace the sheet-metal screws holding the door to the roller disks. This may take several attempts even after you know how.
Open the door and remove the stoppers (inside or outside, depending on the door model), being careful not to let the door unravel. Carefully open the door fully. As soon as the bottom corners of the door clear the tracks on the sides, pull the bottom edge past the tracks, rolling the door tighter. Attach the rope or bungee around the door and tie it to itself. Turn the door two additional turns in the direction as if it were closing, then slide the bottom corners into the tracks. Keep light tension on the bottom edge, and release the rope or bungee.
Pull the door all the way shut, then reopen it. You should feel a slight tension toward opening when the door is nearly open. If not, replace the rope or bungee and tighten or loosen the door one turn. Recheck. When the tension is right, reattach the stoppers. Check that all door hardware is tight and in good shape, clean up and put away your tools.