Why a garage door goes heavy, and what a rebalance does.

Balance, in one paragraph

A door is in balance when the spring's lift matches the door's weight through the whole travel. In that state the door almost floats: it stays where you leave it, half-open included, and an opener only has to steer it, not haul it. Everything else in this guide is what happens as that match drifts.

The half-open test

If the door and tracks are sound, there's a safe way to read the dial above on your own door. Pull the opener's manual release (the red cord), lift the door to about waist height, and let go gently, keeping your hands ready.

Stays put

In balance. The spring is doing its job.

Slides down

Gone heavy. Tension has drifted below the door's weight.

Creeps up

Over-tensioned. Less common, and just as much a job for a technician.

Two cautions before you try it. If the door has already dropped with a bang, or it's sitting crooked or off its track, don't test anything; the spring or running gear may have failed and the door is unsupported weight. And whatever the test says, the fix never involves you and the spring in the same sentence.

Why tension drifts

Springs are consumable. Every open-and-close is one cycle: the spring winds and unwinds once. They're built for a finite number of cycles, and a door that works every day simply spends that budget sooner than one that rarely moves. Around Cardiff the arithmetic has a local flavour: a lot of the valley's doors are original to their post-war houses, so their springs have been spending cycles for decades. The metal fatigues, the coil relaxes a little, and each year the door leans a little more of its weight on whoever lifts it, or on the opener, which will haul a heavy door without complaint until its motor burns out.

What a rebalance actually does

• The door's actual weight is checked against what the spring is holding.
• The spring is re-tensioned with winding bars to match, or replaced if the coil is finished.
• Rollers, hinges, cables and tracks are inspected and lubricated while everything is at hand.
• The opener's force and travel settings are reset for a door that now floats instead of fights.

The result is a door that lifts the way it did when it was fitted, an opener that stops straining, and a spring that isn't being asked to work outside its design. If the spring is at the end of its life, a rebalance won't rescue it, and we'll say so rather than sell you a tune-up that can't hold.

The winding bar rule

Cardiff's first name was Winding Creek. Winding is still the one part of this trade you never improvise.

A torsion spring is set to tension with steel winding bars seated in a winding cone, a quarter turn at a time, by someone braced for the load. Under tension it stores the full weight of the door. Adjusted with a screwdriver, a spanner, or optimism, it lets that energy go all at once. Whatever else you take from this page: the half-open test is yours, the spring is ours.

Heavy, or just old?

Sometimes "gone heavy" is the first line of a bigger entry: a panel taking on water weight, rust in the tracks, running gear worn all round. That's not a rebalance, that's a repair-or-replace decision, and it has its own guide: repair it, or replace it.