Worn Spring
The springs on your garage door are what actually lifts the weight of your door, not the garage door opener as most people think.  

If your springs are worn or broken, your garage door opener is working extra hard to lift your door, which will lead to burning out your door opener and is very Dangerous!

Do Not Do This !!!!!!
The bottom bracket which holds the roller (wheel) closest to the floor, should NEVER be unbolted.

Your springs are attached to the side of this bracket, and it is under tremendous tension.  When unbolted, it will IMMEDIATELY shoot towards the ceiling, possibly taking a few of your fingers with it.