What is a Torsion Bar (Spring Shaft)?
The steel shaft mounted horizontally above the garage door opening that holds the torsion springs and cable drums.
The torsion bar — also called the spring shaft — is a solid or hollow steel shaft that spans the width of the garage door opening, mounted horizontally above the door. It serves as the central axis for the entire spring system: torsion springs are mounted on the bar, and cable drums are attached at each end. When the springs wind and unwind, they rotate the torsion bar, which in turn rotates the cable drums, winding or unwinding the lifting cables. The torsion bar must be perfectly straight and the correct diameter for the weight of the door. A bent or undersized torsion bar can cause uneven door operation, premature spring failure, and excessive wear on the opener. Standard residential torsion bars are 1 inch in diameter; heavier commercial doors may require 1.25-inch or larger bars.