Extension Spring Replacement: inside the visit

Extension springs are common on the detached garages behind older houses, where a low ceiling left no room for a torsion shaft, and those garages are rarely heated. Damp summers, hard frosts and salt carried in on the car pit the spring wire over the years, and a fatigued spring most often lets go on a cold morning when the steel is stiffest. Replacement fits a new pair rated for the door, renews the pulleys and cables that have rusted alongside them, adds containment cables where the original installation never had any, and leaves a door that lifts easily by hand when the power is out.

Pulleys, cables and the hooks that set them

Each side of an extension system has two pulleys, one on the moving end of the spring and one fixed at the front of the horizontal track, and a lift cable that runs from the bottom bracket over both to an S-hook or clip on the track hanger. Each pulley is spun to feel for a rough bearing and looked at for a wheel worn to a sharp groove or wobbling on its bolt. The cables are followed for fraying, rust at the bottom loop and a wrap that has slipped off a pulley. Worn pulleys and cables are renewed with the springs, since a seized pulley is often what shortened the old spring's life.

Fitting a pair that matches the door

The new springs are selected from the door's measured weight and its height, which together give the rating and the stretched length required, and they are fitted as a pair even if one old spring looked sound. The technician checks each new spring's wire size, coil diameter and relaxed length against the specification before it goes up, and confirms the end loops suit the hanger and the pulley fork. The rear loop is hung on the hanger and the front loop takes the pulley fork. On heavier doors that carry two springs per side, all four are renewed together. Nothing is hooked to the door yet; the springs simply hang in place, slack, waiting for the cables.

Lubrication that keeps the new set turning

Twice a year, in spring and before winter, a can of garage-door lubricant does most of the maintenance the springs need. Spray a light coat along each extension spring, working from the hanger to the pulley; it slows rust in a damp garage and quiets the coils. Put a drop on each pulley axle and on the bolts through the pulley forks, then on the hinge pins and roller stems. Leave the tracks dry and wipe them clean, since grease there collects grit and stops rollers rolling. Heavy grease and general-purpose oil are avoided on the springs because they hold moisture against the wire. Run the door a few times afterwards to spread the film.