A torsion spring stores energy by twisting and an extension spring by stretching, and both carry nearly all of the door’s weight so a person or an opener can move it. We replace both kinds on Vancouver and Clark County doors, and the differences that matter are where they sit, how they fail and what keeps them safe.
Torsion springs are the usual setup on sectional doors built in recent decades, and older or lighter doors often carry a pair of extension springs instead. If yours are extension springs and one has broken, converting to torsion is worth pricing beside a straight replacement.
How a torsion system lifts the door
A torsion system lifts the door by twisting springs wound around a steel shaft over the opening, which turns a cable drum at each end of that shaft.
Each spring is anchored at its inner end to a center bearing plate on the header through a stationary cone, and at its outer end to a winding cone that set screws clamp onto the shaft. Turning that cone with proper winding bars loads the spring. As the door rises, the spring unwinds and the drums wrap the lift cables.
Three measurements match a torsion spring to its door: the thickness of the wire, the width inside the coil and the overall length, plus a left or right wind, and a two-spring door carries one of each hand. End bearing plates keep the shaft level and true at both ends, and the lift cables run from the drums down to the bottom brackets on the lowest section.
When a torsion spring breaks, the shaft keeps the pieces where they are. DASMA’s inspection checklist notes that torsion springs mounted on a shaft inherently provide containment, which is why a torsion break is loud but stays put.
How an extension system lifts the door
An extension system lifts the door with a pair of springs that stretch above the horizontal tracks, pulling cables over pulleys down to the bottom corners.
With the door closed, the springs are stretched to their full working length above each track. As the door opens they contract, and the cables, running over a pulley on each spring and another at the front of the track, draw the bottom of the door up and back.
Extension springs are matched to door weight. DASMA’s official color codes mark them by weight in ten-pound steps, with two springs required for the door weight shown. The code only partly identifies a spring, so a replacement is still checked against the door itself.
A broken extension spring has nothing around it. Unless a safety cable runs through its center, the broken end and its hardware can fly across the garage, which is why DASMA’s checklist asks whether every extension spring is restrained.
Torsion vs extension springs at a glance
Torsion springs keep a broken spring on its shaft and work with wall mount openers, while extension springs suit older, lighter doors and need safety cables; the table sets out the rest.
| Point | Torsion springs | Extension springs |
|---|---|---|
| Where they sit | On a steel shaft above the door | Above each horizontal track, one per side |
| How they store energy | Twisting | Stretching |
| How they are sized | Wire diameter, inside diameter, length, left or right wind | Door weight, color coded in ten-pound steps |
| What lifts the door | Cable drums on the shaft | Cables over pulleys |
| When one breaks | Loud bang, a gap in the coil, pieces stay on the shaft | The spring snaps or stretches out; it needs a safety cable to stay put |
| How balance is set | Turns on the winding cone, with winding bars | Spring hook position or cable length at the track |
| Where they are common | Sectional doors built in recent decades | Older and lighter doors |
| Works with a wall-mount opener | Yes, the opener turns the shaft | No, there is no shaft to turn |
Neither system is safe to adjust by hand. The force that lifts the whole door lives in those springs whether they twist or stretch, and DASMA’s checklist reserves spring repairs and adjustments for trained technicians working from proper tools and instructions.
How to tell whether your door has torsion or extension springs
Look above the closed door: springs on a shaft across the header mean torsion, and long springs beside the horizontal tracks mean extension; the four checks below confirm it in about a minute.
- Look above the door. A shaft running across the header with one or two coiled springs on it is a torsion system, and a drum at each end of the shaft confirms it.
- Look above each horizontal track. Long springs running front to back beside the tracks, with pulleys at their ends, are extension springs.
- Look for a cable through each extension spring. That is the safety cable. If there is none, make a note of it.
- Look for a hidden coil. A shaft with drums but no visible spring can still be torsion, because some designs enclose the spring; a photo sorts it out.
One-piece tilt-up doors are a third family, with springs at the sides or a torsion setup and a door that swings out past the opening as it lifts. Our tilt-up door repair page covers them.
Why extension springs need safety cables
Extension springs need safety cables because nothing else holds a broken one: the cable runs through the middle of the spring and is anchored at both ends, so the pieces stay on it instead of flying.
DASMA’s term for it is a containment cable, and its checklist treats one as a basic inspection item; Wikipedia’s garage door article adds that extension springs should always be restrained by one. If yours have none, adding them is a short job against the worst outcome of a spring break, and our extension spring pair price includes a safety cable through each spring.
While you are looking, follow each lift cable too. A cable rubbed thin, kinked at a pulley or slack on one side tells you the system is out of adjustment, and DASMA’s sheet on cycle life adds that rust on the springs themselves shortens their service.
What converting extension springs to torsion involves
A conversion takes out the side springs and pulleys and puts in a full torsion setup above the opening: the shaft, one or two springs, a drum on each end, the plates that carry the shaft, and a new pair of cables.
The header needs solid wood above the door for the spring pad, which DASMA’s glossary describes as the pad that anchors the center bearing bracket, and the opening needs enough headroom for the shaft and springs. On older garages with low headers, that is the first thing we measure.
A conversion makes sense when extension springs break on an older door, when the safety cables are missing and the springs are close to worn out anyway, or when you plan a wall-mount opener, which turns a torsion shaft and cannot work without one.
It costs more than a straight extension spring swap, and the spring replacement cost guide gives the market ranges for both so you can compare them before deciding.