Start with the weight
A typical residential garage door weighs far more than most people expect. Between the panels, the hinges, the struts and any insulation, you are asking a motor the size of a small appliance to move something close to the weight of a heavy piece of furniture, again and again.
If the motor had to lift all of that on its own, it would wear out in a short time. So the door is built with a counterbalance system that takes nearly all the weight off the motor. When the system is working, a properly balanced door feels light enough to lift by hand once it is disconnected from the opener.
Everything in this guide follows from that idea. Each part either stores the energy that lifts the weight, carries it, guides it, or controls when it moves.
Weight is also why safety matters so much with this trade. A garage door is the largest moving object in most homes, and it moves over the heads of people and the roofs of cars. Respecting what it can do is the first step in working around it.
Doors are usually matched to springs by weight, so a lighter door gets lighter springs and a heavy insulated or wood door gets stronger ones. That match is part of what keeps the system calm and quiet when it runs.
The panels and hinges
Most doors are sectional, which means they are made of horizontal panels joined by hinges. As the door rises, the panels follow a curved section of track and fold back overhead to lie flat under the ceiling. The hinges are what allow each panel to tilt relative to the one below it.
Panels may be steel, aluminum, wood or a composite, and they may be hollow or filled with insulation. Their weight and stiffness affect everything downstream, from the size of the springs to the strain on the opener.
Hinges come in different thicknesses, numbered to match the track and the panel position. Hinges at the ends carry the rollers, and hinges in the middle hold panels together. A cracked or bent hinge shows up as a door that rubs, shakes or sits crooked. Our page on hinge and track service covers what we do when they wear.
Rollers and the track
Rollers are small wheels that sit in the track on each side of the door. They roll along vertical track at the sides, then around a curve into horizontal track above. They are what let the door glide instead of scraping.
Rollers are made of steel, or steel with nylon wheels, and the type affects noise and lifespan. Our guide to types of garage door rollers explains the differences. The track itself is formed steel, bolted to the wall and ceiling with angle brackets so it keeps its shape under load.
When a roller wears out, jams or leaves the track, the door can tilt and bind. The track must also be straight and properly aligned side to side. Even a small bend can cause a door to stick or scrape, which is why track and roller condition matters more than most owners realize.
Torsion springs: the heart of the system
Most modern residential doors use torsion springs. These are tightly wound coils mounted on a steel shaft above the door opening. When the door closes, the springs are wound further and store energy. When the door opens, they unwind and give that energy back to help lift the weight.
The springs are connected to the shaft, and the shaft is connected to the door by cables. As the shaft turns, it winds or unwinds the cables on drums at either end. That turning motion is how a coiled spring above the door lifts a panel at the floor.
Torsion springs hold a dangerous amount of stored energy. They must never be adjusted, loosened or removed without proper training and tools. If you hear a loud bang from the garage, a spring has probably broken. Read about broken torsion spring repair and keep clear of the door.
Many doors have one spring, and wider or heavier ones have two. With two springs, the load is shared, and if one breaks the other may still hold part of the weight for a moment, which is a hazard because the door looks nearly normal but is badly out of balance. The usual advice is to replace both when one fails, since they have worked the same number of cycles.
The size of a spring, meaning its wire thickness, length and diameter, is chosen for the specific door. A spring that is too weak leaves the door heavy, and one that is too strong makes it fly upward. This is why we look at the door weight and not just the old spring when we replace one.
Extension springs on older and lighter doors
Some doors use extension springs instead. These are long coils that run along the horizontal tracks on each side of the door. They stretch as the door closes and shorten as it opens, helping to pull the door up.
Extension springs are common on older or lighter doors and are less costly to build, but they behave differently. Because they run alongside the track and not above the opening, a broken spring can whip around, so a safety cable is threaded through each one to catch it.
Both systems do the same job in different ways. We compare them in detail in torsion springs and extension springs explained. For now, the point is that springs, not the motor, provide the lifting force.
Cables and drums: transferring the lift
Cables run from the bottom corners of the door up to drums on the torsion shaft. As the shaft turns, each cable winds into a grooved drum, pulling the door upward. As the door lowers, the cables unwind again.
The cables must stay under even tension on both sides. If one side loosens or slips, the door rises crooked and the rollers bind. A frayed or rusted cable is a safety concern because it carries the full lifting force at the point where it attaches to the door.
Never try to adjust or replace cables yourself, since the tension behind them can cause serious injury. A cable that has come off its drum is a sign that something else has gone wrong, such as a broken spring or an obstruction. See garage door cable repair for how we handle it.
Cable and drum sizes are matched to the springs and to the height of the door. A drum has a spiral groove that guides the cable as it winds, and the cable must sit in that groove. If a cable jumps out, it can bind and cut into the drum or kink, and the door stops lifting evenly.
The center bearing and end brackets
The torsion shaft is supported by bearing plates at each end and, on wider doors, a center bracket. These hold the shaft in position while it rotates thousands of times over its life. If a bearing wears or seizes, the shaft can bind, causing noise or uneven lifting.
On many doors you can see a small bracket at the middle of the shaft where the spring or springs meet. The brackets are bolted to the header above the door, usually into wood framing. A loose bracket can shift under load, so the mounting matters as much as the part itself.
A visual look, with no touching, is enough to notice trouble. Rust streaks, cracks in the plastic bearing or visible movement as the door travels are all worth mentioning to a technician.
The opener: control, not muscle
The opener is the motor unit mounted to the ceiling, connected to the door by a rail and a trolley or arm. When you press the remote, the motor drives a chain, belt or screw that pulls the trolley along the rail, and the door follows.
Because the springs have already done the heavy lifting, the opener only needs to guide the door through its path and hold it. That is why a worn-out spring makes an opener strain, hum or stop. The motor is being asked to do a job it was not designed for.
Openers differ in how they transfer motion. Our comparison of chain, belt and screw drive openers describes the trade-offs in noise, upkeep and cost of ownership.
Inside the opener are travel limits that tell the motor where the open and closed positions are, and force settings that tell it how hard to push before it decides there is an obstruction. If these drift or are set wrongly, the door may stop short, reverse near the floor or push too hard on the ground.
Most of these settings are adjusted by small dials, buttons or a digital menu on the opener. They are worth leaving alone unless you have the manual for your model, because a wrong setting can disable a safety feature. If you notice the door stopping short, that is a good reason to ask for a visit rather than to experiment.
Safety sensors and the auto reverse
Every modern opener is required to include safety features. Two small sensors, one on each side of the door near the floor, send an invisible beam across the opening. If something breaks the beam while the door is closing, the opener reverses.
A second safety feature detects resistance. If the door meets an obstruction, the opener senses extra force and reverses. This protects people, pets and property, and it also protects the door itself.
If a sensor is dirty, misaligned or knocked out of position, the door may refuse to close or may reverse for no obvious reason. Cleaning the lenses with a soft cloth and checking that both indicator lights are steady is a reasonable first step. See safety sensor repair for more.
Weather seals and the bottom edge
The rubber or vinyl strip along the bottom of the door is called the bottom seal. It closes the gap between the door and the floor to keep out water, wind, dust and pests. Around the door frame, additional strips seal the sides and top.
Seals are not a structural part of the lifting system, but they play a role. A seal that is torn, flattened or caught can snag as the door closes, and a gap at the base can let water into the garage.
Coastal and humid areas wear seals faster, since heat and sun harden the rubber. A visual check along the full length of the door, with the light behind you, will often show daylight where there should be none.
Seals also help the building. A tight seal reduces drafts, keeps conditioned air in a garage that is attached to the house, and cuts down on noise from outside. It is one of the least costly parts to replace and one of the easiest to overlook.
Disconnecting the opener: the manual release
Every opener has a way to disconnect the door so it can be moved by hand. This is usually a red cord and handle hanging from the trolley on the rail. Pulling the cord separates the door from the drive so you can lift or lower it manually.
This matters for understanding how the system works because it shows who carries the weight. If the springs are healthy, a disconnected door can be raised by hand with moderate effort. If it feels extremely heavy, that points to a spring problem and not an opener problem.
Use the release only with the door closed when possible, and never when the door is partway open and unsupported, because a worn spring cannot hold it. Our guide to using the manual release explains the steps safely, including how to reconnect the opener afterward.
Balance: the sign of a healthy system
A well balanced door stays where you leave it. If you disconnect the opener and lift the door to about waist height, it should hover or move very slowly rather than slam shut or fly upward. That tells you the spring force matches the door weight.
Balance can drift as springs lose strength over time. It can also change when the door's weight changes, for example after a new coat of heavy paint, added insulation or a windowed panel.
Do not test balance with a door that looks damaged or has a visible spring problem. Our page on balance and adjustment explains what we check, and you can read more in garage door weights and balance.
What wears out first
Not every part ages at the same rate. Moving parts that turn thousands of times, like springs, rollers and cables, tend to wear first. Fixed parts, like panels and track, last much longer if they are not damaged.
Openers fall in the middle. A good opener can serve for many years, but circuit boards, gears and remotes eventually fail. Safety sensors and wall buttons are simple devices that usually fail from dirt, damp or a knock.
- Springs: wear with each open and close cycle.
- Rollers: wear from use, dust and corrosion.
- Cables: fray or rust, especially near the drum.
- Hinges: crack or bend under repeated flexing.
- Bottom seals: harden and tear from sun and moisture.
- Openers: gears, boards and remotes age with use.
What you can check yourself
You can learn a lot about your door by watching and listening. Stand to the side, never under the door, and watch it open and close. Look for jerks, tilts and gaps. Listen for scraping, popping or grinding.
Wiping sensor lenses, testing the remote, replacing a remote battery and looking at the seal are all reasonable. Springs, cables, drums and brackets are for trained technicians only.
If you notice something, write it down: when it happens, what you hear, and whether the door was working normally the day before. That information helps us find the cause. Use the monthly garage door checklist for a routine.
When it is time to call someone
Call for help if the door will not open, if it moves crookedly, if you hear a bang followed by a heavy or stuck door, or if any cable or spring looks damaged. Stop using the door in those cases. Running it can turn a small repair into a larger one.
If anyone is hurt, call 911 first. Otherwise, contact us and describe what you see. We will come to the property, look at the door, explain what we find and what the options are.
Questions and answers
The springs do most of the lifting. They store energy as the door closes and release it when the door opens, which balances the weight of the panels. The opener mainly guides the door along the track and holds it in position. That is why a broken spring makes the door feel very heavy. See torsion spring repair.
Cables connect the bottom of the door to drums on the spring shaft. As the shaft turns, the cables wind into the drums and pull the door upward. If a cable frays, slips or comes off a drum, the door can rise crooked or become stuck. Cable work is dangerous and must be done by a trained technician.
We advise against it. With a broken spring, the door becomes much heavier than the opener was designed to move, and it can drop unexpectedly. Running the opener may strain the motor or damage the door. If you hear a bang or the door feels heavy, stop using it and contact us. We explain what we find before any work begins, so you can decide.
With the door closed and the opener disconnected using the manual release, lift it by hand to about waist height. A balanced door stays roughly in place. If it slams down or rushes upward, the springs are likely worn or out of adjustment. Only try this if no spring or cable damage is visible. See balance and adjustment.
Two small sensors near the floor send a beam across the door opening. If something breaks the beam while the door is closing, the opener reverses. This protects people, pets and property. If a door will not close, dirty or misaligned lenses are a common cause. See safety sensor repair. We explain what we find before any work begins, so you can decide.
Springs, rollers, cables and bottom seals usually wear before panels and track, because they move or flex many times each day or face sun and moisture. Openers can last a long time, but boards, gears and remotes eventually fail. A regular visit helps us spot wear early. See the monthly checklist. We explain what we find before any work begins, so you can decide.