Changing a Roller Without Dismantling the Track
The instinct when a wheel needs to come out is to unbolt the rail, and that is the one thing worth avoiding. The method page at Garage Door Roller Repair Orange County CA 4 Rue Montmartre describes how the intermediate positions on a garage door are dealt with in place, which is how the job stays a parts change rather than a realignment for anyone in Orange County.
Why Unbolting the Rail Is a Bad Idea
Vertical rail is set to a specific spacing and plumb against the face of the door, and the brackets are slotted precisely so it can be adjusted. Take it off and the door has lost its reference. Putting it back within a couple of millimetres of where it was is not good enough, and the result is binding somewhere in the travel that was not there before.
The Bend and Release Method
With the door down and the operator disconnected, the section carrying the wheel is raised until that wheel sits in the curve where the vertical rail turns horizontal. At that point the flange is open enough that the wheel can be tipped out of the channel and the stem drawn from the hinge, and the new one goes back the same way.
Working Through the Set
Done one position at a time, with the rest of the door supported, the whole set changes without a bolt coming out of any rail. Work from the top section downward, keep the door under control at every stage, and never have more than one wheel out of the channel on the same side at once.
Where the Method Does Not Apply
The bottom fixture is the first exception, because it is under cable tension and is dealt with only with the door resting fully on the floor. The top position is the second, since it sits in a bracket that also carries the operator arm on many doors, and that bracket is adjustable in its own right.
Low Headroom Hardware
A door running a low headroom kit has the top section riding in a separate high rail, so the curve trick either does not exist or does not open far enough. On that hardware the manufacturer's own sequence applies, and forcing a wheel past a flange bends the flange.
Before Putting It Back Together
Wipe the inside of the channel while the wheel is out, since this is the only easy access anybody gets to it. Check the hinge hole for wear at the same moment. Then run the door by hand through a full cycle before reconnecting the operator, listening for anything that has changed.