A garage door torsion spring provides the "muscle" for raising and lowering doors. Over time, torsion springs weaken and eventually break. They can be replaced by ambitious do-it-yourselfers, but unless you know the garage door's weight, you can't know which type and size of spring is appropriate for your door. Fortunately, weighing a garage door isn't difficult, and it requires just a few items. Below is a list of equipment needed and the step-by-step procedure to weigh your door:
The equipment you will need
- Analog bathroom scale or other general purpose scale – the simplest, and least expensive, option is to use an ordinary bathroom scale. However, be sure that the scale you choose is analog, which allows for continuous changes in weight readings; some digital scales are designed to take "snapshot" readings, and they may capture a weight during a moment when the door isn't fully seated. In addition, be sure your scale has a capacity of at least 300 pounds to ensure you are able to find the true weight of the door.
- 3 foot section of 2-by-4 lumber – scrap lumber is acceptable, but it should be reasonably flat and stable. For instance, avoid using rotting or softened boards.
- 2 winding bars – these are specialized tools designed to fit the winding cone of your garage door's torsion spring. Depending on the manufacturer, winding cones have different socket shapes—round, square and other shapes—so you will need to purchase winding bars that match the shape. Never use a winding bar that fits loosely; if it slips, the spring can release violently and cause serious injury.
- Step ladder
- An assistant
Weighing your door - a step by step procedure
1. Detach the trolley and opener arm – pull the rope handle that disengages the trolley and remove the bolts holding the opener arm to the garage door.
2. Get your assistant in the correct position – have your assistant stand-ready near the center of the garage door with the scale and 2-by-4 board.
3. Position your ladder beneath the winding cone – the winding cone on the broken spring is usually, but not always, on the left side of the spring. Move the ladder so you can easily reach the cone without having to stretch or extend your body away from the ladder.
4. Insert a winding bar into the winding cone – make sure your winding bar fits snugly in the winding cone's socket. If it feels loose, immediately stop and obtain a properly-sized tool.
5. Rotate the spring using the winding bar – after inserting the winding bar, slowly rotate the cone toward the ground by pulling the winding bar downward. This action should cause the door to begin rising from the ground. If the door doesn't lift, check the cables that translate the rotation into lifting the door. They should be wrapped around the cable drum.
6. Insert the next winding bar – once you have pulled the winding bar downward as far as it will go, continue to hold firmly to the bar so that it won't slip out of the socket. You should see another winding socket come into view in the same approximate position where you inserted the first bar. Insert the second winding bar in the socket, and after being sure you have control of it, carefully pull the lower winding bar free. You can also ask your assistant to pull the bar from its socket if it is too awkward for you.
7. Rotate the spring again with the second winding bar – after transitioning to the second bar, wind downward as you did in step 5. The door should continue to lift and should now be high enough to lower on to the scale. Hold the winding bar steady so the door will not move.
8. Position the scale – ask your assistant to position the scale beneath the center of the door and to place the 2-by-4 board in place on top of the scale immediately beneath the door. Have them be sure the board and scale are both stable and can't easily shift out of position.
9. Check the door for free movement – after your assistant has positioned the scale and board, ask them to grasp the door by its handle and give it a vigorous shake. Before doing so, you need to make sure you have a firm grip on the winding bar and that it can't easily slip from the socket. If the door moves around loosely and doesn't bind, you can continue. Should the door bind or not seem to move, look for warping in the track or other areas of resistance; you may need to contact a professional if you are unable to diagnose the problem.
10. Slowly lower the door – take another glance to makes sure the scale is in position, and your assistant is clear of the door's path. Continue holding the winding bar, and slowly allow the winding bar to move upward naturally. This should cause the door to lower toward the scale. Do not allow the door to free-fall and slam the scale. Once the door is resting on the scale, remove the winding bar.
11. Check the weight – record the weight of the door and contact a garage door installation company for assistance in ordering a new torsion spring that will fit your door's specifications. If you aren't comfortable installing the spring, your garage door repair company can do the job easily and safely.