Torsion and Extension Springs, Explained

The job springs do

A double garage door weighs far more than most people could comfortably lift. Springs store energy as the door comes down and give it back as the door goes up. When they are sized and adjusted correctly, the door is balanced: lifted halfway by hand, it stays there. The opener just guides it.

Torsion springs

Torsion springs wrap around a steel shaft above the door opening. As the door closes, the cables on drums at each end of the shaft wind the springs tighter; as it opens, they unwind and lift. Most Overland Park homes built in the last forty years or so use torsion springs. They move the door smoothly, and a broken one usually stays put on the shaft.

Lighter single doors often have one spring; double doors usually have two. When one of a pair breaks, the other is the same age, which is why many replacements do both.

Extension springs

Extension springs run alongside the horizontal tracks near the ceiling and stretch as the door closes. They are common on older and lighter doors, including many original doors on postwar homes in north Overland Park, Prairie Village and Mission. Because a broken extension spring can fly, each should have a safety cable running through its center, anchored at both ends. Missing safety cables are worth adding.

Enclosed tube systems

Some newer doors use a torsion system sealed inside a tube across the top of the door. The principle is the same; the parts and service steps differ.

How to tell what you have

• One or two coiled springs on a bar over the door: torsion.
• Long springs along both tracks with pulleys and cables: extension.
• A smooth tube across the top with no visible coils: an enclosed system.

Cycle ratings

A cycle is one open and one close. A family that uses the garage as its main door can run several cycles a day. Springs with higher cycle ratings cost more but last longer, so ask what rating an estimate includes.

Signs of wear

• The door feels heavier or will not stay halfway up.
• Gaps or uneven spacing in the coils.
• Rust on the coils.
• The opener strains, or the door rises unevenly.

Cold is often the last straw for a tired spring, and NOAA's climate normals show the Kansas City area has many nights below freezing each winter (NOAA NCEI U.S. Climate Normals).

Why spring work is dangerous

Springs hold a lot of stored energy. The U.S. Consumer Product Safety Commission warns about injuries from garage doors and their hardware (U.S. Consumer Product Safety Commission, garage doors and openers). Winding a torsion spring takes proper bars and experience, and loosening a bottom bracket or cable under tension can release that energy all at once. See broken spring replacement and what shapes spring work.

Related pages: broken garage door spring repair, off-track door & cable repair, garage door repair, and what shapes an estimate.

Sources: U.S. Consumer Product Safety Commission, garage doors and openers; NOAA NCEI U.S. Climate Normals.