How Does a Garage Door Work? The Parts, Springs and Cables Explained

Question 01

How does a garage door work?

A garage door works by counterbalance. Springs carry the door's weight: B&D says they store energy as the door closes and release it to lift the door as it opens. With the springs doing the heavy work, you can lift the door by hand, and the opener only has to move it, not hoist it.

B&D puts it simply: garage door springs have one essential job, counterbalancing the weight of the door. That weight is real. According to B&D, a typical sectional door weighs anywhere from 80kg to 150kg, or more for a double. Steel-Line says its own roller doors can approach or exceed 150kg. Steel-Line adds that without springs, most garage doors would be almost impossible to lift by hand, or the automatic opener would burn out trying.

Here's the cycle on a door with torsion springs, the type Steel-Line fits to its sectional doors:

1. 01As the door comes down, its weight twists the springs above the opening. Steel-Line says torsion springs twist as the door closes, storing the energy.
2. 02With the door shut, that stored energy sits in the springs, ready to go.
3. 03When you lift the door, by hand or with the opener, the springs unwind and give the energy back, so the door feels light.
4. 04Extension springs, which Steel-Line uses on its tilt doors, do the same job by stretching instead of twisting.

Question 02

What are the parts of a garage door called?

The main parts of a garage door are the door itself (a curtain, panels or one solid panel), the springs, the lifting cables and drums on sectional doors, the tracks or guides it runs in, and the opener. Which parts your door has depends on its type: roller, sectional or tilt.

Want to know which door type suits a garage, rather than how each one works? The roller vs sectional vs tilt comparison covers headroom, noise, insulation and wind.

Question 03

Where are the springs on a roller, sectional and tilt door?

On a roller door, the spring is hidden inside the barrel the curtain rolls around. On a sectional door, torsion springs usually sit on a shaft above the opening, though some designs use extension springs along the tracks. On a tilt door, extension springs stretch at each side as the panel moves.

Steel-Line says roller door springs are hidden within the cylinder and are less likely to snap. On sectional doors, Steel-Line says torsion springs can be fitted as single or dual systems, depending on the door's size and weight. B&D says torsion springs sit horizontally above the door, while extension springs run along the sides of the horizontal tracks. Steel-Line also notes that the spring type is set by the door design, not by homeowner preference.

A spring that has failed usually tells you. B&D says a snapped torsion spring can sound like a firecracker. If a door suddenly feels very heavy or lifts crooked after a bang, read what to do about a broken spring and leave the door where it is. Thom handles spring repairs across the Sunshine Coast.

Question 04

What do the cables on a garage door do?

On a sectional door, the lifting cables connect the bottom of the door to the cable drums above it. As the springs turn the drums, the cables wind on and lift the door evenly from both bottom corners. On extension-spring doors, Steel-Line says separate safety cables are essential, stopping a broken spring from snapping loose.

B&D's Panelift sectional door instructions show each lifting cable fixed to a bottom hanger at the base of the door and attached to the cable drum at the top. Steel-Line says safety cables are essential on extension springs, stopping the springs snapping loose if they break.

Cables wear over time. B&D says to check the cables regularly for corrosion, fraying or tangling, and to call your service provider if you find any. Look, but don't touch or try to refit a cable yourself.

Question 05

What is a garage door drum?

A garage door drum is the round part the cable or curtain winds onto. On a sectional door, cable drums sit on the spring shaft, one on each side, and wind the lifting cables on as the door opens. On a roller door, the barrel or drum is what the whole curtain rolls around.

Sectional cable drums have a spiral section that the cable winds along. B&D's Panelift troubleshooting lists cables in the wrong position on the spiral of the drums as the cause when a door balances at the floor but runs up or down in between. B&D also says that on low-headroom garages, the size of the cable drums and spring gear can start to eat into headroom, which is when its rear torsion layout becomes an option.

On a roller door, the barrel turns on an axle clamped at each end. B&D's roller door instructions warn that the axle must be securely clamped, otherwise the door will lose spring tension. Steel-Line's manual also says not to loosen any fasteners on the spring assemblies, including the shaft to bracket fixing, so the brackets at each end of a roller door are a technician's job. For a roller door that feels heavy or won't stay up, see roller door spring tension.

Question 06

What do the tracks, wheels and guides on a garage door do?

Tracks and guides keep the door on its path. A sectional door has wheels on each panel that run in vertical tracks, around a curve, and back along horizontal tracks under the ceiling. A roller door's curtain runs in guides at each side. A tilt door swings on side arms around a pivot point.

Clean tracks matter more than oily ones. Steel-Line's roller door manual says to keep the tracks free of oil or grease, because grease in the tracks attracts dirt and dust that builds up. It singles out brick dust from brickwork and paving. B&D's roller door instructions say plainly: do not grease the guides.

A bent or misaligned track is a different story. B&D says to call a professional for safe track realignment. If a sectional door has run crooked or a wheel has popped out, book garage door repairs rather than forcing it back.

Question 07

Where does the opener sit, and does it have to be in the middle of the door?

Not always. On a roller door, B&D puts the opener beside the door rather than above its middle. A sectional door's opener sits on the ceiling, behind the door when it's open. Either way, B&D says the springs take the strain so the motor doesn't burn out.

Openers also have safety features built in. B&D says automatic reverse immediately reverses the door if it senses an obstruction stopping it closing. Safety beams, where fitted, sit at the base of the door and shoot an invisible beam from one side to the other. The safety sensors and auto-reverse guide shows how to test both.

When the power is out, the opener can be disconnected so the door runs by hand. The manual release guide covers doing that safely. Steel-Line says that without springs an opener would burn out trying to lift the door, so an opener straining against a suddenly heavy door is a sign to stop and call.

Question 08

Why does a garage door need to be balanced?

A balanced door takes about the same effort to open by hand as to close. B&D says that's the test for a well set-up sectional door, and that a poorly running door may reduce the effective life of the opener. Springs lose tension over time, so balance drifts and a service checks it.

B&D says it is natural for springs to lose tension over time. When a sectional door hangs unevenly, B&D's own fix list checks that the cable lengths are equal and that both springs have equal turns. Those are spring and cable adjustments, so they're a job for a technician with the right tools, not a home fix. Steel-Line makes a related point about roller doors: tension too loose and the door may stop opening and closing properly, too tight and it puts stress on the door's parts.

A garage door service covers five checks: spring tension and balance, roller and track lubrication, hardware tightening, cable and drum inspection, and an opener and safety-reverse test. For a quiet check of your own first, see whether the door feels noticeably heavier one way, or listen for new grinding or squealing. The noisy garage door guide helps match a sound to a part.