Extension Spring Replacement
Removing and replacing extension springs on residential overhead doors. Covers opening and securing the door so the springs are at rest, disconnecting the operator, identifying and matching spring specifications, removing the old springs, inspecting pulleys/cables/brackets, installing required safety containment cables, mounting and routing the new springs, lowering the door under control, and balancing, tension-adjusting, and final testing before returning the door to service.
Warnings
This procedure must only be performed by trained, qualified door service technicians. Extension springs under tension can cause serious injury if mishandled.
Extension springs are under tension when the door is closed. A spring or cable that breaks under tension can cause serious injury.
ALWAYS replace extension springs in matched pairs, even if only one has broken. The remaining spring has the same cycle count and will likely fail soon.
Safety containment cables MUST be installed through the center of every extension spring. This is not optional — it is a critical safety requirement per DASMA and UL standards. If existing springs lack safety cables, install them with the replacement springs.
Never disconnect a spring from its mounting point while it is under tension. The door must be fully open (springs at rest) before disconnecting.
Keep hands and fingers clear of pulleys and cable attachment points.
Required PPE
- Safety glasses
- Leather gloves
- Steel-toed boots
Tools Required
- Replacement extension springs (matched pair) — correct weight rating and length
- Safety cables (if not already installed — required on all extension spring systems)
- Adjustable wrench and/or socket set
- Vise grips / locking pliers (2 pair)
- Pliers
- Stepladder rated for your weight plus tools
- Tape measure
- C-clamps or door clamps
- New lift cables (if frayed or worn)
- S-hooks or clip-style connectors (as required by spring type)
- Lubricant (light machine oil)
Procedure — 8 Steps
Step 1
Open the Door, Secure It, and Disconnect the Operator
This procedure must only be performed by trained, qualified door service technicians. Extension springs under tension can cause serious injury if mishandled. If the door cannot be opened because both springs are broken, carefully prop the door open using a sturdy support and a helper. The door is extremely heavy without spring counterbalance — do not attempt to hold it by hand alone.
Raise the door to the fully open position. Extension springs are at their resting (zero tension) state when the door is fully open. Clamp C-clamps or vise grips to the track below the bottom roller on each side to hold the door in the open position. Alternatively, use a sturdy prop under the door. The door must not be able to close during the procedure. Once the door is secured open, disconnect power to the automatic operator (unplug or breaker off) and pull the emergency release to disengage the trolley from the door.
Pro Tips
- Extension springs reach zero tension only at the fully open position — confirm the door is all the way up before trusting the springs are relaxed.
- Set the C-clamps or vise grips on the track just below the bottom roller on each side so the door physically cannot roll closed.
- A sturdy prop under the door is a good backup to the track clamps, especially if you are working alone or if a spring is already broken.
- Kill power at the breaker or unplug the operator, then pull the emergency release — this removes any chance of the motor driving the door during the job.
Checklist
Training Videos
Disclaimer: These videos are produced by third-party YouTube channels and are not affiliated with Doorbot. Video content may not align exactly with the procedures above, may depict techniques that differ from DASMA or manufacturer recommendations, and may show tasks that are dangerous if performed without proper training and equipment. Always follow the written procedure, your company's safety policies, and applicable industry standards. Use these videos as supplementary reference only.
References & Standards
- DASMA TDS-190 — Factors Affecting Spring Cycle Life
- Door manufacturer installation manual
- IDA / Longen Foundation — Extension Spring Safety Cables