You hear the bang from the garage and find the door sitting half-open, one side lower than the other, the opener straining against a load it cannot move. When the technician arrives and opens the system up, they find one broken torsion spring — and immediately recommend replacing both. You ask why you need to replace the one that is not broken.
Single torsion spring systems carry the full door weight on one spring — failure is sudden and complete. Dual systems split the load between two springs that age together cycle for cycle. When one breaks, the other has accumulated the same fatigue and will fail soon after under doubled load. Always replace both springs on a dual system at the same time. Understanding the difference between single and dual torsion spring systems — and why pair replacement is not an upsell but a straightforward maintenance decision — is what this article covers. With thousands of 5-star ratings across Google, Yelp, Facebook, and Thumbtack, Local Garage Doors replaces torsion springs across California and Nevada daily, and the pair replacement conversation comes up on virtually every dual-spring job we run.
If your spring has already broken and you need same-day service, call 
866-337-1631, 
email info@localgaragedoors.com, or schedule your appointment today. If you want to understand what you are dealing with before the technician arrives, this is the article to read first.
How Torsion Springs Work and What the System Is Actually Doing
A torsion spring mounts horizontally on a steel shaft directly above the garage door opening. When the door is closed, the spring is wound under tension — storing energy in the form of torque. When the door opens, that stored torque unwinds through the shaft, rotating the cable drums at each end, which pull the lift cables attached to the bottom corners of the door. The spring energy counterbalances the door’s weight so precisely that the opener only needs to supply a small additional force to start the door moving. A properly balanced torsion-spring door lifted by hand with the opener disconnected should hold at waist height without rising or falling.
This is a precision counterbalance system. The spring — or springs — are wound to a specific torque that matches the actual weight of the door. Get that torque wrong, and the door is either too heavy for the opener to lift smoothly or too light and rises faster than it should. Get it right, and the system operates with almost no effort from the motor, extending the life of the opener, the cables, and the rollers by keeping the door in a state of near-weightlessness during travel.
Single Spring Systems: How They Are Set Up and Where You Find Them
A single torsion spring system has one spring mounted on the shaft, typically positioned at the center above the door opening or slightly offset to one side. One spring carries the full counterbalance load of the door on its own. The shaft still has drums at each end connected to cables on both sides of the door — the single spring winds and unwinds to lift both sides simultaneously through the shaft.
Single-spring torsion systems are most commonly found on lighter, smaller doors — standard 7-foot single-car doors, lighter steel doors without insulation, and older doors where the single-spring configuration was the standard at the time of installation. You will find single-spring setups regularly across older Sacramento and Bay Area tract homes where the original garage door was a lightweight single-car with a basic opener, and on older Las Vegas and Henderson properties where builder-grade single-car doors were the norm in the development.
The mechanical reality of a single-spring system is that there is no redundancy. The spring carries the entire load every cycle. When it fails — and all springs eventually fail, since they are rated in cycles with a finite lifespan — the door immediately loses all counterbalance. The opener tries to lift the full unbalanced weight of the door, the motor either stalls almost immediately or the auto-reverse triggers, and the door stops working until the spring is replaced. There is no graceful degradation. A single-spring failure is an immediate full stop.
This is also why a single spring, when it does break, breaks with a noticeably louder report than one spring in a two-spring system. The single spring is storing the full counterbalance torque on its own, and when that stored energy is suddenly released through a fracture in the coil, the entire load transfers to the shaft and cable drums at once. Homeowners across Sacramento, the Bay Area, and Las Vegas who have experienced a single-spring failure often describe it as sounding like a gunshot inside the garage.
Dual Spring Systems: Load Sharing and How the Pair Works Together
A dual torsion spring system has two springs on the shaft — typically one wound left and one wound right, positioned on either side of the center bracket, each contributing half the total counterbalance torque needed to support the door. On a standard insulated double-car steel door, each spring is wound to carry roughly half the door’s weight, and the two work in concert through the shaft to lift both sides evenly.
Dual spring systems are the standard on heavier doors — most double-car doors, insulated doors, and heavier single-car doors across California and Nevada. The additional spring is not just about capacity. It is about load distribution and redundancy. Each spring carries half the torque load per cycle, which means each spring is being stressed to a lower degree per wind-and-unwind than a single spring carrying the full load would be. Theoretically, two springs sharing the load should accumulate fatigue more slowly per spring than a single spring carrying everything alone.
The practical benefit of a dual system also shows up at the point of failure. When one spring in a dual system breaks, the surviving spring still holds approximately half the counterbalance torque. The door does not drop completely — it becomes significantly heavier, and the opener will typically stall or trigger its force-sense protection, but the remaining spring prevents the door from falling freely. This partial redundancy is why dual-spring failures are often noticed as the door becoming much harder to move or the opener ghost-stopping rather than the sudden, complete failure that single-spring breaks produce.
The wire gauge, coil count, and spring length in a properly specified dual system are calculated to deliver exactly the right combined torque for that door’s weight. This is why spring sizing is not interchangeable — the two springs in a pair are specified together, and replacing one with a spring of a different gauge or length throws the combined torque off balance, even if the replacement spring is itself a good-quality product.
Why Both Springs in a Dual System Are Always the Same Age
This is the core of the pair replacement conversation. Two springs in a dual torsion system are installed at the same time, wound to the same spec, operating on the same shaft, and cycling together every time the door opens or closes. Every cycle that fatigues the steel in the broken spring has also fatigued the steel in the surviving spring to exactly the same degree.
A spring that has logged 9,800 cycles on a 10,000-cycle spring is not a spring with 200 cycles of useful life remaining — it is a spring that has accumulated 98 percent of its rated fatigue load and could fail at any point in the remaining 200 cycles. The fact that it did not break on the same cycle as its partner is a function of minor manufacturing variation, small differences in exactly where each spring was wound relative to its rated spec, and the randomness inherent in fatigue failure in any material. It does not mean the surviving spring is healthy.
Local Garage Doors makes pair replacement the standard recommendation on every dual-spring job because the alternative is a mathematically predictable second failure in the near future. The surviving spring is at the end of life, regardless of whether it broke first. When we are already on-site with the shaft exposed, the springs fully unwound, and the cables off the drums, installing a second new spring is a fraction of the total job time and cost. Coming back for the second spring break — which means another service call at full labor, another morning with the vehicles stuck, another emergency situation — costs significantly more than doing both springs correctly the first time.
What Happens to the System When One Spring Breaks and the Other Survives
The moment one spring in a dual system breaks, the surviving spring immediately takes on a load it was never designed to carry alone. The dual system was wound and calibrated to deliver the full counterbalance torque as a pair. When half of that pair disappears, the surviving spring is now the only source of counterbalance for the full door weight — it is doing the job of two springs with the capacity of one.
Every subsequent cycle, the door runs in that state, which stresses the surviving spring at roughly double its design load per cycle. The fatigue accumulation that was progressing at a controlled rate under normal two-spring operation is now accelerating dramatically. A spring that might have had several hundred cycles of normal-load life remaining can fail in a fraction of that time under doubled load. We have responded to calls across Sacramento, the Bay Area, Las Vegas, and the Arizona communities we serve, where a homeowner replaced only the broken spring, and the surviving spring failed within weeks — not months — because it had been running overloaded since the first break.
There is also a door balance issue that begins immediately. The two drums on the shaft are designed to receive torque from both springs simultaneously and distribute that torque equally to both cables. When only one spring is providing torque, the distribution is no longer equal — one cable is receiving more lift force than the other, and the door starts to travel unevenly. This uneven travel puts lateral stress on the tracks, accelerates roller wear on the side that is working harder, and eventually causes the door to bind in the tracks if the imbalance is not corrected. The spring and cable inspection we perform after every spring replacement includes a manual balance test — disconnecting the opener and verifying the door holds at waist height — precisely to confirm the system is properly calibrated before we leave the job.
The Cascade Risk: What a Single Spring Break Can Trigger in the Wider System
A broken spring rarely fails cleanly on its own. The shock load that travels through the shaft when a spring fractures can affect the cable drums, the setscrews holding the drums in position, and the cables themselves. Local Garage Doors inspects all of these components during every spring replacement — not because they always need attention, but because a spring failure event can loosen setscrews, cause a cable to jump its drum groove, or shock-load the bottom bracket where the cable attaches to the door.
We also inspect the top section of the door panels where the opener bracket connects. On a single-spring failure, the opener may have attempted to lift the full unbalanced door before the auto-reverse triggered, and that attempted lift places significant stress on the top section reinforcement. If the top section is an older panel without adequate strutting, or if the opener bracket has started to pull away from the panel, the spring failure is the moment that stress becomes visible. Catching it at the spring replacement visit is the right time — not when the panel fails separately on a future cycle.
Single Spring Systems: When Upgrading to Dual Makes Sense
Most older single-spring setups can be converted to dual-spring systems during a replacement, and Local Garage Doors often recommends this conversion when a single spring reaches the end of life on a door that has been re-insulated, re-paneled, or otherwise made heavier than the original spring specification assumed.
The conversion makes practical sense in several situations. A single-car door that has been upgraded from a lightweight steel panel to an insulated door is carrying more weight than the original single spring was sized for, which means the spring has been running above its design load and failing faster than its cycle rating would predict. Converting to a two-spring system at that point correctly distributes the higher load across two springs, each of which can be wound to the right torque for the door’s current weight. Homes in Lake Tahoe, Truckee, and the Sierra foothills, where heavily insulated doors are common for energy retention, also frequently benefit from this conversation during a replacement visit.
The conversion is not always warranted — if the door is still the original lightweight single-car panel and the single spring has simply reached the end of life at its rated cycle count, a like-for-like single-spring replacement at a higher cycle rating is perfectly adequate. The right answer depends on the door’s current weight, the headroom available on the shaft for a second spring, and what the homeowner wants in terms of future service frequency. We assess all of this during the spring and cable inspection and walk through the options before recommending anything.
Why Pair Replacement Is Not Optional on a Dual System
The question we hear most often on dual-spring jobs is some version of “why can’t I just replace the one that broke?” You can — the door will technically function. But the surviving spring is already at the same fatigue point as the one that just broke, and it is now carrying the full door load while the new spring settles in. Its failure is weeks to a few months away, not years.
The labor cost of that second call is identical to what you are paying now. The shaft has to be exposed again, the springs unwound again, the cables rethreaded again. Paying the incremental cost of the second spring while we are already on-site is the only version of this job that makes financial sense. We make this recommendation on every dual-spring job and let the homeowner decide. The ones who skip the second spring almost always call back within a few months.
Why Both Springs Come Off the Door Together
Single torsion spring systems carry the full counterbalance load on one spring — failure is immediate and complete. Dual torsion spring systems share that load equally between two springs that are always installed, operated, and aged together. When one spring in a dual system fails, the surviving spring has logged the same cycle count, is now carrying doubled load, and is statistically close to its own failure. Replacing both springs simultaneously on a dual system is the correct repair — not because the surviving spring looks broken, but because it is already at the same point in its fatigue life as the one that just broke and will fail under accelerated load in the near future if left in place.
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email info@localgaragedoors.com.
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Frequently Asked Questions
Why do both garage door springs need to be replaced at the same time?
Both springs in a dual system are installed together and cycle together. When one breaks, the surviving spring has logged the same number of cycles and is at the same fatigue point. Replacing only the broken spring leaves an end-of-life spring doing double duty, which accelerates its failure significantly.
How do I know if I have a single or dual torsion spring system?
Look at the horizontal shaft directly above your garage door opening. If you see one spring running the length of the shaft, you have a single-spring system. Two springs mounted side by side with a center bracket between them is a dual-spring system. Most double-car doors use dual springs.
What happens when one spring breaks on a two-spring door?
The surviving spring takes on the full counterbalance load it was never designed to carry alone. The door becomes very heavy, the opener stalls or triggers its force protection, and the door may travel unevenly. The surviving spring is now accumulating fatigue at roughly double its normal rate.
Can I convert from a single to a dual torsion spring system?
Yes, in most cases. We recommend the conversion when a door has been re-insulated or re-paneled with heavier material since the original single spring was installed. The heavier load is better distributed across two springs, and each spring runs within a more comfortable stress margin.
How long does it take to replace torsion springs?
A standard dual-spring replacement typically takes one to two hours on-site, including unwinding the old springs, installing and tensioning the new pair, rethreading the cables onto the drums, and running the balance test to confirm the door holds at waist height.
Related Articles:
- Torsion vs Extension Springs: Identification Guide and What Each Means for Service
- Spring Cycle Ratings Explained: What 10,000, 20,000, and 50,000 Cycles Actually Mean for Your Garage Door
- Garage Door Closes Unevenly Then Auto-Reverses: Cable Tension Imbalance Explained
- How to Tell If Your Garage Door Springs Are Failing — Before They Break?
