Correct Torsion Spring Tension for Garage Door Installation: How to Get It Right Before You Close the Door
The correct tension setting for torsion springs is one of the most technically specific and safety-critical aspects of a garage door installation. Get it right and the door operates smoothly, requires minimal effort to move, and the mechanical components last for their full rated life. Get it wrong — overtension or undertension the springs — and the door will be unbalanced, the opener motor will work harder than it should, and in the worst case, components can fail in a way that damages the door, the vehicle inside, or injures anyone nearby.
This guide explains how torsion spring tension works, how it is calculated and set correctly for different door weights and sizes, how to verify the tension is right after setting, and why this is not a task that should be approached without the proper knowledge and tools.
How Torsion Spring Tension Works
Torsion springs store and release energy through rotation. When a garage door closes, the closing movement pulls cables that are wound around drums fixed to the ends of the torsion spring shaft. This pulling action rotates the shaft and winds the spring tighter, storing rotational energy as tension. When the door is opened, that stored rotational energy unwinds, turning the shaft in the reverse direction and lifting the door through the drum and cable system.
The tension in the spring is measured in turns — specifically, the number of quarter-turns (90-degree increments) wound into the spring beyond its neutral state. Each quarter-turn adds a specific amount of torque that corresponds to a specific lift force on the door.
The goal of correct tension setting is to wind the spring with precisely enough turns to make the door effectively weightless at any point in its travel — meaning it neither falls under gravity nor floats upward from excess spring force. A correctly tensioned door, when stopped midway between open and closed, will hold its position without drifting.
How Torsion Spring Turns Are Calculated
The number of turns required for correct torsion spring tension is calculated from a formula that combines three variables: the door weight, the drum circumference, and the spring’s torque coefficient (which is determined by the spring’s wire diameter and inside diameter).
The standard calculation used in the Australian garage door industry is:
Turns required equals door height (in metres) divided by the drum circumference (in metres), with an additional quarter-turn added as a compensating wind for the door weight bias at the closed position.
For a standard 2100mm high door on a 101.6mm circumference drum (the most common drum in residential systems), the base calculation produces approximately 7 to 7.5 full turns. For a 2400mm high door on the same drum, it is approximately 8 to 8.5 turns.
However, these base figures assume the spring is correctly rated for the door’s weight. If the spring torque coefficient does not match the door weight, the base turn calculation alone will not produce correct tension. This is why spring selection and tension winding are interdependent calculations — they cannot be treated independently.
The Role of Door Weight in Tension Calculation
Door weight is the critical input to the entire tension calculation. A spring sized and wound for a 70kg door will be significantly undertensioned if fitted on a door that actually weighs 100kg. The resulting imbalance means the spring is not doing its counterbalance job, and the full door weight is being borne by the opener motor (in an automated system) or by the person lifting it manually.
Door weight is determined by the door’s dimensions (width x height), material type, panel gauge, insulation, and hardware fitted. Reputable manufacturers publish their panel weight specifications. Where weight is uncertain — such as on an older or unbranded door — weighing the door using a luggage scale attached to the lifting point on the bottom panel is the most reliable approach before ordering springs or setting tension.
The Winding Process: Tools and Safety
Winding torsion springs is done using a pair of winding bars — solid steel rods that fit into the winding cone at the end of the spring. Each quarter-turn is applied by inserting the winding bar into the winding cone hole, applying force to rotate the cone (and with it, the spring), then securing the bar and moving to the next hole for the next quarter-turn increment.
The forces involved are significant. A torsion spring under 7 to 9 turns of tension stores hundreds of Newton-metres of rotational energy. A winding bar that slips, breaks, or is released incorrectly can strike with enough force to cause serious injury. This is not an exaggeration — spring winding injuries are documented in the Australian workplace injury record.
The tools required for this correctly are:
Two properly sized solid steel winding bars — never a screwdriver or a piece of rebar. Length must be sufficient to provide adequate leverage while keeping hands clear of the spring. Safety glasses. A secure ladder positioned to the side of the spring, never directly in front of the winding cone. Knowledge of the correct turn count before beginning, verified against the door weight and drum specifications.
How to Verify Correct Torsion Spring Tension After Setting
Once the springs have been wound to the calculated turn count, the installation requires a balance test before the opener is engaged or the door is used normally. Here is the standard verification process used by professional garage door installers across Australia:
Disconnect the opener if one is installed to put the door in manual mode. Lift the door manually to approximately halfway open (around waist height). Release the door without holding it. Observe what happens.
A correctly tensioned door will hold its position with minimal drift — maybe one or two centimetres of movement in either direction before stabilising. If the door drifts down toward the closed position under gravity, the springs are undertensioned and more turns are needed. If the door floats upward toward the open position, the springs are overtensioned and turns need to be removed.
For double torsion spring systems (two springs on the same shaft), both springs are wound to the same calculated turn count, and the balance test applies equally. One spring winding slightly differently from the other will result in uneven door travel where one side moves faster than the other — a condition visible as the door racking or skewing slightly in the track during operation.
Common Tension Mistakes and Their Consequences
Undertensioning: The most common mistake, often resulting from estimating the turn count without accurately knowing the door weight. The door feels heavy manually, the opener motor draws higher current and runs hotter than it should, and the spring and cables experience higher loads than their design anticipates because the spring is not doing its share of the work.
Overtensioning: Less common but equally problematic. An overtensioned spring can cause the door to fly upward when released, potentially breaking the top section connection points, derailing the cables from the drums, or causing the door to fly out of the track. In a worst case, an overtensioned door that is released manually can strike the open position stop bolts with enough force to damage the track or horizontal bracket.
Mismatched turns between double springs: Results in door racking, where one side of the door leads the other during opening or closing. This places shear forces on the panel joints and progressive wear into the track on the lagging side. Correct matching requires both springs to be wound identically turn for turn.
When to Adjust Tension After Initial Installation
Springs can stretch very slightly over the first few weeks of use as the new wire settles under operational loads. A minor balance check and possible quarter-turn adjustment at the four to six week mark after initial installation is good practice. After this initial settling period, spring tension should remain stable until the spring’s rated cycle life is approached and the spring begins to lose torque capacity — at which point the door will progressively feel heavier as the spring weakens, signalling that replacement is approaching.
Contact Opal Garage Doors for Professional Torsion Spring Setting
At Opal Garage Doors, every torsion spring installation is wound to the correct tension based on precise door weight measurements and drum geometry — not approximations or generic online tables. Our technicians carry the correct winding tools and perform a full balance test on every installation before the job is signed off. Whether you need springs fitted on a new sectional garage door or springs replaced on an existing system, contact our team to book a service visit anywhere across Australia.