You'll need to release the tension in the torsion spring before you begin working on the garage door. Start by clamping adjustable locking pliers onto the torsion spring shaft and wedging the pliers against the header wall above the door.
Insert a steel rod into one of the holes in the spring winding cone, which has four holes used for loosening and tightening.
Hold tightly to the rod, and loosen the setscrews holding the winding cone in place.
Use the steel rods to loosen the spring one-quarter turn at a time. Alternate the two rods, using one to hold the cone steady and the other to turn the cone after the first rod is removed.
After the tension has been released, disconnect the existing garage-door opener from the door.
Begin removing the door panels. Start at the top panel, and remove the hinges connected to the panel below (Image 1). Be careful when dealing with glass.
Disconnect the track by unscrewing or unbolting it from the doorframe.
If you're planning to replace your automatic door opener, remove the opener's track from above (Image 2) and remove the opener (Image 3).
Begin installing your new door. If you're installing a two-car garage door, place a reinforcing bar on the top panel to prevent the door from bowing in the center. Be sure the bar is centered on the panel. Drill pilot holes (Image 1), and secure the bar with screws.
Attach hinges to the top of each panel (Image 2). Many new doors come with pilot holes drilled by the manufacturer.
Attach axle supports to the bottom of the bottom panel and to the top of the top panel.
Place the bottom panel into the door opening. Hold the panel upright by driving a nail into the wall next to the panel and bending it over to hold the panel in place (Image 3). Make sure it's level before attaching the next panel.
Attach the next panel on top of the first one. Make sure the groove of the upper panel rests on the ridge of the lower panel. Repeat the process until all the panels are in place. The final panel should extend 1" or so past the top of the door opening.
From inside the garage, secure the top half of each hinge to the panel above (Image 1).
Place the wheeled axles into the side hinges and the top and bottom axle supports.
Begin installing the track by attaching brackets to the vertical track pieces. Check your instruction manual to be sure you're installing the brackets in the correct places.
After attaching the brackets, place them against the wall, and make sure the wheels lie properly in the track (Image 2). Attach the door cable to the hook on the bottom panel axle support before attaching the bottom bracket to the wall (Image 3).
Assemble the pieces to support the spring assembly, and attach them to the track (Image 1). Check the instruction manual to make sure you're installing the assembly in the correct place.
Rest the curved portion of the track on the vertical piece you installed earlier (Image 2), and attach the other end to the ceiling bracket (Image 3). Use the same ceiling supports that were used with the old door.
Attach the horizontal track to the vertical track on the door. Don't tighten the bolts firmly until you're sure the door fits properly and lines up smoothly.
Drill a hole through the horizontal track to line up with the vertical track. Use the holes in the vertical track to determine where to drill the hole.
Bolt the tracks together. Be sure to use the correct size bolt: if the head is too big, it will obstruct the track.
Locate the center of the opening, and mark it on the door header. You will attach the support for the spring there later.
Attach the spring anchors to the springs (Image 1), then attach the spring locking cone. The locking cone must be on securely: it keeps the spring from popping loose under high tension.
Bolt the two springs securely to the main header bracket (Image 2).
Slide the torsion rod into the holes in the side header brackets (Image 1). Make sure the rod is secure, then attach the pulleys to each end of the rod.
Secure the center header bracket to the center mark on the header (Image 2). You'll probably need to lift the center of the assembly to get it level before attaching it.
Bring the cable up from below, and attach it to the pulley wheel on both sides (Image 1). Turn the wheel so the slack is pulled tight over the pulley from the door side. Slide the wheel to the header bracket, and tighten it securely (Image 2).
Tighten a pair of locking pliers to the rod on the outside of the bracket. This will prevent the rod from turning when you begin to tighten the springs.
Snap a chalk line across the springs. This will help you know how many times you've turned the springs when you begin tightening.
Use the steel rods to tighten the spring by reversing the loosening procedure you used on the old door. Check your owner's manual to determine how many turns are required to tighten the spring. Look at the chalk line to confirm how many turns you've made.
When you reach the appropriate tension, tighten the bolts in the anchor to lock it in place, and remove the pliers from the torsion rod.