2.3 Beware of older winding cones. These older Crawford and McKee torsion spring cones were made for 5/8" bars. Sometimes, however, the holes are too small for 5/8" bars. Whatever you do, don't use a 1/2" bar; instead, grind down a 5/8" bar to fit. I recently had a McKee spring let loose after winding because I used a 1/2" bar when my 5/8" bar wouldn't fit. Just before it let loose I was telling myself, "This is not safe." And it wasn't. The only safe way to replace these older springs is to make a winding bar for each hole of each cone. http://www.youtube.com/watch?feature=youtube.be&v=Z_eZc-kh40c
If you are in an emergency situation, you can lift the door manually while using the garage door opener, but this is not recommended. The door could get stuck halfway up and then slam the rest of the way down. This could cause injury. The ideal solution is to call a Twin Cities garage door repair company to come quickly and repair the spring so that normal operation can be restored and so you are not in a situation where you find yourself having to attempt manual lift with or without the assistance of the opener.
In most cases, only one spring breaks or wears out at a time, and you can get away with replacing just the failed spring. But this is a little like replacing old car tires one at a time. You'll get the best performance if all the springs are new and have the same strength. Extension springs are replaced individually, making it more tempting to replace just one. With torsion springs, you have to disassemble everything to replace either spring, so it makes sense to swap out both springs during the repair.