The cables and pulleys on a 1970s Dunwoody extension-spring door
From the doorway into the garage it looks like the door gave up on one side. One bottom corner sits on the slab, the other hangs a few inches higher, and a cable droops along the track on the low side. On a door with its springs stretched along the tracks, that picture almost always starts with the cable and what it runs over.
Why did a 1970s garage door with springs along the tracks come off its track?
One side stopped lifting while the other kept going. On a door with extension springs, the springs along each horizontal track lift the door through one cable per side. When one cable run drags, slips off a pulley or gives out, that side falls behind and the door racks until its rollers leave the track. The fix starts along the cable’s path, the work behind off-track and cable repair in Dunwoody.
A wood door from the first build-out in Kingsley, Mill Glen, Village Mill or Dunwoody Club Forest that was never converted still lifts this way, and on those doors the track is usually fine. A straight track with a crooked door hanging in it points up at the cables.
How does the cable run on a door with extension springs?
Each side has its own cable, and it doubles back on itself. From the bottom bracket on the door’s lower corner, it runs up beside the vertical track to a pulley fixed near the front of the horizontal track, back to a second pulley riding on the end of the stretched spring, then forward to a tie-off at the front.
The springs do the lifting through those cables, the spring’s pulley traveling about half as far as the door, and both sides have to pull evenly the whole way. On a torsion door the cable winds onto a drum at the end of a bar over the opening instead.
What wears out along that cable path?
The pulleys and the cable where it bends. Every time the door moves, two pulleys a side turn under the cable, and on a door that has been cycling for decades their bearings, bolts and grooves wear along with the steel strands passing over them. All of it can be read from the garage floor without touching anything.
- A pulley whose bearing has dried out or seized. It squeals a beat into every lift, or stops turning, so the cable drags across it instead of rolling with it.
- The fixed pulley at the front of the track tilting on its bolt as the door moves. A worn bolt or a cracked fork lets the cable climb out of its groove and off the side of the wheel.
- A flattened or frayed stretch of cable where it bends over a pulley or loops through the tie-off, visible as a shiny flat spot or a few loose strands standing out from the rest.
- Rust where the cable meets the bottom bracket, closest to the slab, worst on a garage that takes driveway runoff at the threshold.
The sign that ties them together shows well before the door leaves the track. It starts rising unevenly, one side a beat behind the other, with a gap opening under one bottom corner as the door comes off the floor.
Can the door run once a cable has jumped its pulley?
No. Unplug the opener, leave the door where it stopped and keep people and cars out from under it. On that side the spring can still be stretched, held only by a cable pinched beside its pulley, so the pro unloads the spring before anything else is touched.
The safety cable threaded through each spring keeps a spring that breaks from flying across the garage, and it does nothing to hold the door. If the car is shut in behind it, that is what emergency repair for a car stuck in the garage is for.
What gets replaced with a frayed cable on an extension-spring door?
Both cables, as they have run the same years over the same pulleys, and any pulley that is worn, seized or wobbling on its bolt goes at the same visit. A new cable over a dry pulley starts wearing in the same spot as the old one. With the springs unloaded, the new cables go on set even side to side.
The springs get a look while the pro is up there, being the same age as the cables. If they are near the end as well, that visit is a natural point to weigh converting the door to a torsion spring instead of rebuilding the pulley setup.
Then the door is reset in its track and balanced, and the opener’s force setting is re-checked and brought down to suit a door that no longer drags. Both cables replaced and the door rebalanced runs $150 to $260, with any pulley added on the quote at the house. Reseating rollers and realigning a door that came out of its track is $150 to $350. The price page lays out what a cable job costs here beside the rest of the Dunwoody repair list.
When it is time to call: cable and off-track repair in Dunwoody, extension-spring doors included.