Spring Failures on Merrillville's Seventies Door Stock

Most doors around here run a torsion shaft mounted across the wall above the opening, with the spring wound onto it and a cable dropping from a drum at each end to the bottom brackets. A wide two-car door usually carries two springs on that shaft, wound in opposite directions.

Older detached garages, and a handful of original attached ones, still use the extension layout instead: a long spring stretched along each horizontal track. Those want a safety cable threaded through the middle of the spring and anchored at both ends. It does nothing at all until the day the spring parts, at which point it is the only thing standing between a length of loaded steel and whatever is parked underneath. Where they are missing, they go on with the new springs.

There is no universal spring. Wire gauge, coil diameter, wound length and the direction of the wind combine into one figure — how much lift the spring delivers — and that figure has to match what your particular door actually weighs. Where the stamp on the old cone is legible we read it. Where it is not, or where the door has been changed since it was fitted, the door goes on a scale and the set is worked back from the weight and the drum size.

On a door carrying two springs, both come off. Leaving the surviving one in place is a false economy: it has done identical work in the same garage, so the second call is usually weeks away, and an uneven pair pulls the door out of level in the meantime. Once the new set is wound, the drums are re-indexed so both cables carry the same share, the door is tested by hand at mid-travel with the opener unhooked, and the motor's reverse function is checked before we leave.