The weight of the doors varies, but they are among the heaviest items in your home. It is important for your safety that they are well maintained. The door should open smoothly and quietly. There should be no shaking. When shaking noticed, it is often because of a loose or cracked bracket. You should take the time to check each item. If a bracket breaks, a portion of the door could fall on your car or on a family member.
Many people think that the garage door opener does all of the heavy liftings, but it is the torsion springs that allow the door to open smoothly. The rollers along the side enable the door to slide up quietly and quickly. The cables prevent the door from falling too fast and assist with the lifting. Most of those components, as well as the main door, are held in place by brackets of some kind.
The 5″ center bearing bracket is under high tension. If it is cracked and needs to be replaced, you should call a professional.
There is a pair of brackets at the top inside corners of most overhead residential doors. They can work loose over time. Their function is to hold the top roller carrying fixture in place. On the bottom of your door is another pair of brackets. They can become damaged with time as well. If the door is left open frequently, they may be exposed to the elements and become rusted. Their purpose is to support the bottom roller and help to hold the cables in place.
There are specialty brackets for doors with low headroom. They are durable and long-lasting but could need to be replaced if the door is getting older. In additions to the brackets, there are bearing plates that can work loose or suffer from wear and tear.
Most brackets (other than the center bracket) and bearing plates are sold in pairs by garage door specialists. Home improvement stores sometimes sell a single bracket or plate. Replacing only one bracket is unwise. If one has become cracked or broken, the other one is likely to go soon.
The brackets are relatively inexpensive. If they fail the door could be irreparably damaged. Remember that this door is one of the things that keep your house secure. Always look to the real experts for advice, before listening to a self-trained handyman.