Garage Overhead Door Extension Spring Question

[Junkman]

The extension spring on my overhead door broke today. Looking at the spring, it has tan paint at the end. Its collapsed length is 25", and the spring on the other side is extended out to 70". This door has a low headroom clearance adapter and it is just about impossible for me to get it up enough to get a scale under it. Doing online research, the tan spring is for a 100 # door, and that would mean that each panel weighs 25 # each. The door panels are steel interior and exterior and insulated between the two steel panels. I was wondering about the amount of distance that the present spring are extended, and was wondering if I should go with a heavier spring that would accomplish the same lifting force as the present spring, but not stretched out as much. The door has a Liftmaster chain drive track lifting system and everything was installed about 30 years ago. I am enclosing pictures so you can see what I am working with. The roof joists are 16" on center.

 

[Improved700]

I had long springs like, until one let loose. I could not find a replacement at the local Manards/HD/Lowes, so had to go with shorter spring, and change the rear mounting location. I ended up buying 2 new springs and replaced both sides at the same time.
If you can find another tan spring with the same extension, I would purchase that and save yourself the hassle of changing the current setup.

Make sure the safety cables are in place. Neither one of mine had it. When the spring let loose, it caused a hell of bang.
I was near it when it happened. Needless to say, I had to go inside and change my pants !

 

[Jlbc212]

The springs are stretched by the cables which are attached to the bottom fixtures on the door. For a door that is 7ft (84") high, the springs with the pulley arrangement will stretch from their relaxed length about 42", a distance closely approximating half the height of the door when the door is fully closed. Generally speaking when the door is at the fully up position the spring is not completely relaxed. The installer pulls the fully relaxed spring about 2" to 3". This slight stretch keeps the door in the open position. Added together the total measured length of a fully stretched spring for a 84" high door should approximate 70" (25", the relaxed length, plus 3", plus 42"). The springs are engineered to exert a specific maximum amount of pull corresponding to the expected length of stretch. The only sure way to determine the correct replacement spring is to weigh the door and measure the door's height. Color codes can vary among the different door and spring manufacturers. Too short a spring will overstretch it and the spring will soon lose its elasticity and its designed pull. Too long a spring will never achieve its designed pull.

 

[NUTTSGT]

I've put in the 5 garage doors at our place and no expert. Those springs, I'll call someone in to do those things. I had in my garage that I replaced during the refurb... scared me taking it down.

I'd call a door company to put a new pair in.