Torsion Spring

A torsion spring is a helically coiled steel spring mounted horizontally on a steel shaft (the torsion shaft) that runs through its center, positioned directly above the closed garage door. When the door closes, an installer winds the spring a set number of turns using winding bars inserted into the winding cone. That winding twists the spring and stores mechanical energy, the same way twisting a rubber band stores energy. As the door opens, the spring unwinds and releases that energy, transferring torque through the shaft to the cable drums at each end, which wind up the lifting cables and pull the door upward.

Torsion springs are the dominant counterbalance method on modern sectional residential doors. A single spring is common on lighter doors up to about 200 pounds, while heavier or wider doors use two springs side by side on the same shaft. Duplex (double-wound) configurations exist for tight headroom situations.

Key specs you will encounter:

• Wire diameter (measured in inches or thousandths): determines the spring's torque rating and stiffness. Residential springs use a range of wire sizes; a spring supplier or installer selects the appropriate diameter for the door weight and cycle-life target.
• Inside diameter: typically 1-3/4 inch or 2 inch for residential springs.
• Cycle life: standard springs are rated for about 10,000 open/close cycles, which works out to roughly 7-10 years of average use. High-cycle versions are available with ratings well above the standard minimum.
• IPPT (inch-pounds per turn): the torque the spring delivers per revolution; used to match the spring to the door's weight.

For example, a two-car steel door weighing 250 pounds typically uses two torsion springs, each contributing roughly 125 pounds of counterbalance force. If the spring is wound correctly, the door should stay at any height you set it when disconnected from the opener.

Because a fully wound torsion spring stores enormous energy, the industry strongly cautions against DIY adjustment. The winding cone on the right end of the spring accepts winding bars, and if a bar slips during winding, the released energy can cause serious injury. The spring system is the part of a garage door that technicians treat with the most respect.

The center bearing plate anchors the spring assembly at the mid-span of the shaft, and the end bearing plates support each end. Together these components form the core of the counterbalance system.