Every garage door uses one of two spring systems. They do the same job, counterbalancing the weight of the door, and they go about it in completely different ways.
Tell them apart in five seconds
Stand inside the garage with the door closed and look up.
| Torsion | Extension | |
|---|---|---|
| Where it sits | One or two springs on a steel bar mounted horizontally above the door opening | Two long springs running parallel to the horizontal tracks, one on each side, up near the ceiling |
| What it does | Twists | Stretches |
| How it looks | Tight coil wound around a bar | Long open coil that visibly lengthens as the door closes |
If the springs are above the opening, you have torsion. If they run front to back along the sides, you have extension. Most San Diego homes built in the last 30 years use torsion.
How each one works
Torsion springs twist. As the door comes down, cables wind onto drums at each end of the bar and load the spring by twisting it. That stored torque unwinds to lift the door. Because the force comes off a bar mounted to the wall, the lift stays even across the whole travel, and both sides of the door get the same amount of help at the same time.
Extension springs stretch. They pull against pulleys and cables as the door lowers, storing energy by extending. On the way up they contract. It works, and it is a simpler and cheaper system to install, but the force is not as even. Extension springs give more assistance at one point in the travel than another, which is why doors on them can move in a slightly jerkier way.
The safety difference, which is the real one
Both systems store a large amount of energy. What matters is what happens when one lets go.
A torsion spring breaks in place. It is wound around a steel bar, and when it fails the bar absorbs most of the force. You hear a bang like a gunshot, and the spring stays where it is with a visible gap in the coil.
An extension spring is under tension along its length and is attached at each end. When one snaps, the stored energy has somewhere to go, and pieces can travel across the garage at speed.
If you have extension springs, check for safety cables
A safety cable runs through the middle of each extension spring and anchors at both ends. When the spring breaks, the cable catches the pieces instead of letting them fly.
Look along each spring. You should see a cable threaded through the centre of the coil. If there is no cable, that is the single most important thing to fix on your door, and it is a small job. Older installations often skipped them, and plenty of doors in San Diego still have none.
Lifespan
Springs are rated in cycles, not years, where one cycle is the door going up and coming back down. The commonly supplied grade is 10,000 cycles, which at four openings a day works out at about seven years. Higher-cycle torsion springs are available and can run several times that.
Torsion generally outlasts extension for the same usage, because a wound spring on a bar takes load more evenly than a stretched one taking it end to end. Extension springs also tend to lose their shape over time, which shows up as a door that sits slightly crooked or feels heavier on one side.
Work out where your springs sit in their life →
Which is better
Torsion, for most doors. It handles weight better, lasts longer, runs more smoothly, and fails in a far more controlled way. Every heavy, wide, or insulated door should be on torsion.
Extension still has a place. It costs less, and it works where there is not enough headroom above the opening to fit a torsion bar. Low-ceiling garages and some conversions genuinely need it.
Can I convert from extension to torsion?
Often yes, and it is a worthwhile upgrade on a heavy door. It needs enough clear headroom above the opening for the bar and brackets, so the answer depends on your garage rather than your door. We can tell you on a look.
What does not change between them
Neither is a homeowner repair. A wound torsion spring stores enough energy to break an arm, and winding bars slip. A tensioned extension spring under load is no safer to unhook.
Both should also be replaced in pairs. They were installed on the same day and have run the same number of cycles, so when one goes the other is not fine, it is next. On extension springs this matters even more, because two springs of different ages pull unevenly and drag the door out of square.
Not sure what you are looking at? Take a photo from inside the garage with the door closed and text it to us. We will tell you which system you have, whether it has safety cables, and whether anything looks close to failing. That costs nothing.