Definition
What is an extension spring replacement?
Extension springs are the long, thin coils that run alongside the horizontal tracks on each side of the garage door. They stretch as the door closes and pull back as it opens, using that stored tension to share the door's weight. When one wears out or snaps, the door loses its counterbalance on that side.
An extension spring replacement installs a matched pair of new springs, with safety cables, and rebalances the door. It's a different system from the bar-mounted coils covered in our torsion spring replacement guide, and the parts, hazards and fixes aren't interchangeable.
Extension springs show up most often on lighter doors and older installations. If you're not sure which type you have, our overview of how spring repair works explains how to tell the two apart in a minute.
Methods
How do extension springs work?
Each spring is attached to the door through a cable and pulley arrangement. The spring sits parallel to the horizontal track, anchored at the back end to a bracket near the ceiling. A cable passes around a pulley at the front end and connects to the bottom of the door.
When the door is closed, the springs are stretched to their longest. As the door rises, the springs shorten and release tension, which is why a closed door with working springs feels light to raise. At the top of the travel, the springs are relaxed and the door is supported mostly by the tracks.
The weak point is the stretch itself. Extension springs flex a long way on every cycle, and the pulleys, cables and anchor brackets all carry that load. Wear in any of them can look like a spring problem, so a careful inspection looks at the whole assembly.
A safety cable should run through the center of each spring and attach at both ends. It does nothing in normal use, but when a spring snaps it keeps the broken pieces from flying across the garage.
Symptoms
8 signs of a broken or worn extension spring
Extension springs fail in ways you can often see from the floor. Look for these.
- A sharp snap or crack. A snapped spring is usually loud, and it can be sudden.
- A spring that hangs loose. Part of the coil sits slack beside the track or has fallen away.
- A stretched, sagging spring. A coil that looks longer than its twin has lost tension.
- A door that tilts or rides up on one side. The weaker side lags behind.
- A door that won't stay open. It rises and then drifts down on its own.
- A door that slams shut. Without tension, gravity does the work.
- Visible rust or fraying. Rust on coils, or a worn safety cable, points to age.
- Noisy pulleys. Squealing or wobbling pulleys can precede cable and spring failure.
Our guide on how to tell if your garage door spring is broken compares these signs side by side and shows what to do next.
Why it happens
Why extension springs fail
Stretch fatigue is the first cause. An extension spring is pulled to near its limit on every close, and over thousands of cycles the steel weakens and eventually breaks, usually near one of its ends where the stress is highest.
Environment matters too. Hot, humid conditions across the Southeast encourage rust, and a rusty spring has weak spots. Rust that flakes off also creates rough surfaces that rub against the safety cable.
Mismatched springs are a quieter problem. When one spring in a pair is replaced and the other is left, the older spring does more of the work and the pair never balance perfectly. Doors that have gained weight from new panels, insulation or glass also overload springs that were rated for a lighter door.
Finally, hardware wear plays in. Bent pulleys, stretched cables and loose brackets change how the spring pulls and can shorten its life.
Before you call
Safe checks before you call
These steps are safe from the floor with the door closed, and they give a provider a head start.
- Compare the left and right springs. Note any that hang loose, look longer or are missing sections.
- Check whether each spring has a cable running through it.
- Look at the pulleys for wobble, rust or cracks, and at the cables for fraying.
- Photograph both sides of the door from a safe distance.
- Note the door size, and the label or color tag on the spring if you can see one.
A broken extension spring can swing violently if it isn't contained by a safety cable. Stay back from the tracks, keep children and pets away, and never stand under a door that isn't moving normally.
Step by step
What a professional extension spring replacement involves
A provider works methodically because extension springs release energy suddenly. Here's what a typical visit looks like.
- Relieve the tension. The door is raised and secured so the springs are relaxed before anything is loosened.
- Inspect both sides. Springs, pulleys, cables, track brackets and rollers are checked for damage.
- Identify the springs. Length, strength rating and end style are matched to the door's weight.
- Remove the old springs. The pair comes out, with the old safety cables if present.
- Fit the new pair. New springs go in with fresh safety cables running through the coils.
- Replace worn hardware. Frayed cables and worn pulleys are changed while the assembly is open.
- Adjust the tension. Both sides are set equally so the door rises level.
- Test and lubricate. The door is cycled several times, moving parts are lubricated, and the opener's safety reverse is checked.
Pricing
What affects the cost of extension spring replacement
Quotes vary by door and by provider, and we don't publish prices. These are the main cost drivers.
| Factor | Why it matters |
|---|---|
| Spring length and rating | Longer or stronger springs for heavier doors cost more. |
| Safety cables | Adding cables where none exist adds parts and labor. |
| Cables and pulleys | Worn pulleys and cables are often replaced along with the springs. |
| Like-for-like or conversion | Swapping to a torsion setup is a bigger job than replacing the same type. |
| Time of the call | Urgent or after-hours visits can be priced differently by some providers. |
Request a written estimate that itemizes parts and labor before work starts. To see how those numbers break down, read what affects garage door spring replacement cost, or start with the Montgomery spring repair overview for the full picture.
Urgency
When a broken extension spring is an emergency
Treat it as urgent when the door can't be secured, a snapped spring is hanging loose, or someone is trapped on either side of the door. A door that is partly open and unstable is also a priority, because it can drop without warning.
Keep everyone away from the tracks and call. Our emergency garage door repair page covers what you can do safely while you wait.
FAQ
Extension spring replacement FAQs
Do both extension springs need to be replaced together?
Yes, replacing the pair is the standard approach. Springs of different age and stretch lift unevenly, which tilts the door and wears the tracks and cables. A matched pair keeps both sides lifting with the same force.
Do extension springs need safety cables?
They should have them. A safety cable runs through the middle of each spring and is anchored at both ends, so a snapped spring can't whip across the garage. If yours has none, ask the provider to add them during the repair.
Can I convert extension springs to a torsion system?
Often, yes, if the garage has enough headroom above the door and a solid mounting point. A conversion uses different parts and more labor than a like-for-like swap. Our guide to torsion spring replacement shows what the newer system involves.
Why does my door tilt after one spring broke?
One side is now lifted by a working spring and the other side by nothing. The door rides up unevenly, and the cable or rollers on the weak side can slip. Stop using the door until both springs have been inspected. Our guide on how to tell if a garage door spring is broken lists the other signs to look for.
How long do extension springs last?
Life depends on the cycle rating and how often the door is used. Many are rated for a limited number of cycles, so a daily-use door can wear a pair out in a handful of years. See how long garage door springs last for a way to estimate.
Can I keep using the door with one broken extension spring?
No. The door loses balance, the working spring is overloaded, and the opener has to carry far more weight. The sensible move is to stop using the door and arrange a proper repair.