Garage door springs are designed for specific garage doors. They are finally adjusted on site during installation. They should not be swapped for other than an exact replacement.

Spring technology is imprecise at best. Spring manufacturers freely acknowledge this. But then the garage door springs aren't high-tech items.

Most of us believe that the garage door springs open and close our garage doors. Not quite right.

Springs are NOT made to open and close garage doors. Garage door springs are designed to ASSIST the user to open and close the door. You are required to use only a little effort to open and close the garage door because of the springs' action.

When properly set up the door gear and springs are working properly, only a little effort is needed to finish the movement; a gentle push up or pull down; just a little push, or pull.

So if you feel that you have to struggle to open or close your garage door, it might be that the springs are not adjusted properly. But it also means that the garage door opener might not suitably like replacing you or another two legged door opener.

So the garage door lifting mechanism - mainly the springs - should be adjusted to ensure the movement is as smooth as it can possibly be.

This how to test for proper spring tension. A properly lubricated garage door having springs that are in the perfect condition should stay suspended in a part-open position. If your door closes without assistance the spring needs more tension. If on the other hand, the door is thrown open, the springs tension should reduced. Any adjustment should be equally made to each spring spring or pair of springs. See here for canopy doors.

Your garage doors' dead weight can mean that it could take more than one person to lift a single panel of some doors. So you can well imagine what the hazards can be if the springs are not working properly and the door tends to close or open due to the sprigs tension.

Garage doors can be very heavy. Depending on the size and materials they can anything between 300 to 400 pounds. So they need to be seviced. Don't wait for a component failure

Homeowners realize that garage doors do need to be serviced though the work is usually limited to using a squirty can to lubricate the moving parts.

Garage doors are used every day, several times every day. It follows that they need a lubrication service.

The rollers, hinges, springs, pulleys, cables - everything that moves is subject to wear and tear. Components wear out. They get old slowly and a component failure can be disastrous.

You'll understand the difficulty caused if the springs and gear are not working properly.

Here's the best advice. Whatever you think is required to put matters right when difficulty rears up, you are probably wrong. Anything with springs of this style - especially the torsion springs can inflict serious damage on an untrained character like the average man or woman.

If you think you can, you probably can't, without proper instruction, and even then it can be disastrous through lack of experience.

Call an expert to do the job. If the garage door opener is to work with a torsion spring at the top of the door running the door width then this is a quite different matter. That is hideously dangerous. Don't do it untill you talk to an expert.

Now - I know that I've said that because I have to. But I know that some people have been successfull  when taking advice from an experienced installer.