On a lot of older doors, and plenty of newer budget ones, there is no spring above the opening at all. Instead there are two long springs running alongside the ceiling tracks, one on each side, stretching out every time the door comes down. They are extension springs, and they are a perfectly respectable way to balance a garage door.
They have one requirement that is very easy to miss, because when it is missing, nothing looks wrong. Nothing looks wrong right up until a spring breaks.
How an extension spring door works
With the door open, the springs are short and relaxed. A lift cable runs from each bottom corner of the door up to a pulley at the front of the track, back to a pulley on the end of the spring, and forward again to an anchor. As the door closes, those cables drag the springs out along the track and they store energy. When the door opens, the springs pull back in and the cables lift the door.
A fully stretched extension spring on a double door holds a great deal of energy in a straight line, and it is made of steel that suffers the same fatigue as any other spring. When it lets go, all of that energy goes somewhere. With nothing to stop it, the somewhere is the broken end of the spring, the pulley, or the hook, travelling at speed across the garage.
The cable that should be there
The answer is old and simple: a safety containment cable, a thin steel cable run straight through the center of each spring and anchored at both ends, near the front of the track and at the rear hanger. In normal use it does nothing whatsoever. The spring stretches and relaxes around it. When the spring breaks, the cable keeps the pieces on the line, and they drop and dangle instead of flying.
These are not exotic parts. Door manufacturers and the industry’s own safety guidance have recommended them for years. They are also the first thing to go missing when a spring is replaced in a hurry, and on a door installed as cheaply as possible they may never have been fitted at all.
How to check yours in a minute
- Door fully open, and stand to the side. The springs are relaxed and at their shortest, which is the safest time to look. Look, do not touch.
- Look down the middle of each spring. You should see a straight cable running through the coils and fixed at both ends. If you can see through the spring to the ceiling beyond, it is not there.
- Check both ends of that cable. One looped around the rear hanger and hanging loose at the front is not containing anything.
- Look at the spring ends. Rust, a hook that has started to open up, or coils that no longer close up tight when the spring is relaxed, all belong to a spring near the end of its life.
- Look at the pulleys. A wobbling pulley, a flattened groove, or a lift cable fraying where it runs over the wheel is a separate problem with the same ending.
Why these doors deserve a second look
Extension springs are not worse than torsion springs, only different. They are cheaper to fit and they suit lighter doors well. Many of them are in older garages, which also means many of them are on their second or third set of springs, fitted by whoever happened to be available each time, and each of those visits was a chance for the containment cable to end up in the bin.
They also break differently. A torsion spring that snaps is loud, and the pieces stay on the shaft above the door. An uncontained extension spring can hit the car, the wall, or whoever is standing beside the track. It breaks when it is stretched, which is when the door is closed or closing, which is exactly when people are in the garage.
The money question
No prices. Containment cables are among the cheapest parts in this trade. If they are missing and the springs are healthy, fitting them means working with the springs relaxed, so the door is open and the job is careful rather than long. If the springs are near the end anyway, the sensible visit is new springs, a pair, with new containment cables in the same trip, so the door stays level and nobody has to come back.
The expensive case is the one where a spring has already broken without containment and taken something with it. That bill is usually from the body shop, not from us.
What not to buy
- Do not buy a spring replacement that leaves the containment cables out. Ask to see them go back through the new springs. It takes minutes.
- Do not buy a torsion conversion because someone said extension springs are unsafe. A contained extension spring system is safe. Converting can make sense for other reasons, a heavier door or less noise, but not that one.
- Do not buy the trick of moving the spring hook up a hole. Shortening a tired spring to make a heavy door feel lighter buys a few weeks, and it means the spring is holding more energy on the day it finally breaks.
- Do not buy springs by color alone. The color code tells you what a spring is rated to lift. What has to match is the door, and doors gain weight over the years from paint, added insulation and replacement panels.
The short version
If your springs stretch along the ceiling, there should be a cable running through the middle of each one. It costs almost nothing, it does nothing on an ordinary day, and on the one day that matters it keeps a broken spring on a lead.
It is the smallest part we fit, and the one we are happiest to find someone else already fitted.
J&A Garage Door Repair · (707) 200-7682 · jagaragedoorrepair.com
Lic. 1133099 · Serving Sacramento and the Central Valley.