Garage door extension springs - fine tuning


So I noticed the other day that the pull cables on my extension spring garage door had fallen off of the pulleys (the ones vertically aligned with the door when its down) on both sides.
I decided to start by replacing the cables. The pulleys all seem fine - they turn and are not bent in any way. I did this on one side, and I noticed the instructions sort of breezed over how tight you should make it (ie where to secure the other end of the pull string to the fixed position on the ceiling). I basically placed it such that, when the door was open, the cable would remain just taunt between the pulleys so that they would not sag.
I then took a closer look at the side which I had yet to replace. I noticed that, when the door is fully opened, the wire sags severely between the pulleys. There is no chance it would stay on without any tension. Here are my questions: 1) While working, I had the garage door fully pulled up so that it was completely flat in the opened positoin (and braced with clamps). I can't remember for sure, but I assume that in normal operation it never goes up that far - it must stay down a bit where the last segment actually bends slightly. If this is the case, I think the cable has a better chance of staying in the pullys, but right now I don't even think my newly installed side would stay this way. So, does the pully system rely on the door never being completely horizontal?
2) Does the sagging indicate that my springs need to be replaced? They still seem to pull up the door when the pully remains on the track, so I assume they are OK.
3) What is the proper method for setting the tension of the pull cable in a resting position? I'm concerned about it being too loose and causing the cable to fall off the pulleys in the up position, or it being too tight and causing breakage of the springs in the down position.
Thanks, jeff
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I think the point is that the door should open and close easily and smoothly under manual operation- adjust as needed to achieve this.
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jeff37 wrote:

It may not "rely" on that, but I can't recall seeing an overhead sectional door where the bottom section ended up fully horizontal when "up".

I have always adjusted the spring tension by trial and error so that the door's weight is just balanced when the door is raised half way up, and it'll "hang" at that position without having to hold it. If the springs are correctly sized to the weight of the door, that should do it.
Do you have "safety cables" running through the spring bores? If you don't, do yourself and others a favor by picking up a set and installing them. They cost less than ten bucks and it only takes a few minutes to hook them up. The head you save could be your own if a spring decides to snap and flail around whilst you're standing in the wrong spot.
Safety cables will help prevent the "spring sag" you mention as well as any flopping about which might be what's causing the cables to flop off the pulleys.
(another Jeff)
--
Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)
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Thanks. Answer is yes, I do have safety cables installed. They are very slack though. I read somewhere this was supposed to be the case - they should not provide any tension but just hold things in place if the springs decide to go. Are they supposed to be more taunt? This install looks pretty sloppy, so it wouldn't suprise me if they didn't do it correctly. Then again, I think it must have been running OK like this for years because its fairly old. (I only moved in 6 mos ago).
Thx Jeff
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The safety cables should be taught (not sagging nor tight) from the backhang to the horizontal track front. The sole purpose is to keep the spring from flying across the garage if it breaks.
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Thanks all for the suggestions. I THINK I set up the tension correctly, but I am having other problems. I need some help determining if they are related.
After I installed the new cables, I was able to tension them such that the door opened and closed fairly smoothly without much effort. I hooked up the opener and was able to open close 3 or 4 times with no problem.
Then, I went to test it again later, and it kept getting stuck. I tried pulling it up and down manually and noticed that it was randomly and sticking in either direction. If I keep pushing or pulling, the thing won't budge in these cases. However, if I let up on the pressure, or briefly change directions, it'll usuall slide right through whichever spot it was previously sticking on.
I don't see any obvious obstruction. The rollers all seem to roll, and the thing is evenly in the tracks. What the heck else could it be? The biggest difficulty here is that it seems to stick randomly, in any given spot, going in either direction. I have to assume its somehow related to the pull cables having falled off the tracks earlier - seems like too much of a conincidence otherwise. Could this be a problem with my tensioning, or some kind of damage from when the cables were off the pulleys?
Thanks, Jeff
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It sounds like the tension on the cables is unequal causing the door to get cocked in the opening. The opener pulls from the center of the door, so unequal spring tension will cause one side to go up higher and the whole door will be sideways in the tracks.
You might also want to check the distance from the track to the rollers on each side, you don't want a big gap - you should be able to grab a roller stem and move it about and inch at most sliding in the hinge. A quick fix may be to just take a hammer to the track brackets and nudge them closer to the inside of the opening (if there is room for adjustment), otherwise you may need to whip out the impact gun or drill and re-set the tracks by moving the lag screws.
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"Safety cables will help prevent the "spring sag" you mention as well as any flopping about which might be what's causing the cables to flop off the pulleys. "
I don't think that can be emphasized enough. I remember about 50 years ago in the infancy of overhead doors, having one snap in my dads garage. It tore up everything in its path, including a sturdy angle braced 2 X 4 mount for the top end, that it broke in half. It sounded like the house exploded
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Adjust it so there is just enough tension on the springs to keep the cables on the pulleys when the door is fully raised. You are correct that the safety cables are there 'just in case' and should be relatively loose.
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