Torsion vs. Extension Garage Door Springs: Which Do You Have?
How to tell torsion and extension garage door springs apart, how each is sized differently, and the specific safety hardware each one needs.
Most residential garage doors use one of two spring systems, and they're sized, installed, and made safe in completely different ways. Knowing which one you have is the first step before looking up any replacement.
How to tell them apart
- Torsion springs mount horizontally on a metal shaft directly above the closed door — usually one or two thick coiled springs centered above the door opening.
- Extension springs run along the horizontal tracks above the door, one on each side, stretching and contracting as the door opens and closes.
Sizing works differently for each
Torsion springs are sized by wire diameter, inside diameter, length, and wind direction — chosen to hit a required torque calculated from the door's weight and drum radius. Extension springs are sized much more simply, by picking a standard off-the-shelf pull-weight rating (like 150# or 200#) close to half the door's weight, since two extension springs are the standard setup.
Different safety hardware, different failure modes
| Torsion springs | Extension springs | |
|---|---|---|
| Stores force by | Twisting under torque | Stretching under tension |
| Key safety hardware | Winding bars, secured ladder | Safety cable through the spring's center |
| Failure risk | Sudden violent unwinding | Spring becoming a projectile |
Whichever type you have, use the Garage Door Spring Calculator to get a starting torque, turns, or rating estimate, and always confirm the exact spec against your existing spring before buying a replacement.