A standard door opens by swinging on its hinges, and the door itself doesn't actually come into contact with the ground (unless the hinges are in fact loose). This means that there is no friction and standard doors can avoid the types of operational problems that other doors might encounter. Since sliding doors slide back and forth along the ground, there is continual friction when opening or closing the door. This is how the door works. But when this friction becomes too much (making the door difficult to operate), you will need to do something about it. So what can cause excessive friction when using your sliding door? And how can you fix the issue?
Dirt and Debris
Check the track that the door slides along. The edge of the track creates a groove, and it's all too easy for dirt and debris to accumulate here. This accumulation means that there is dirt and debris between the base of the door and its track, creating that annoying friction. It's as simple as cleaning this track on a more regular basis.
Open the door and vacuum the track, and then close the door and do the same. This is so that the entirety of the track is accessible for the vacuum cleaner. You might want to use a narrow brush attachment (if your vacuum cleaner has one) to ensure that all the dirt and debris are more effectively removed. If this a solution you've already tried, there are other options you can try if there is still too much friction when operating your sliding door.
Have you ever lubricated the base of your sliding door? Almost any standard lubricant will do the trick, just as long as it deposits a viscous oil that will be gradually worked into the tracks of the door with usual operation. Spray in short, controlled bursts, and you might want to put some newspaper along the ground next to the sliding door's tracks. This is just in case some of it makes it onto the floor since it will result in a legitimate slipping hazard that can be difficult to remove. Still experiencing too much friction? There's something else you'll want to try, and you'll need a screwdriver.
Your sliding door runs back and forth on small rollers at the base and top of the door. Over time, the tension of these rollers can begin to subside. This essentially lowers the door to the point that it's metal sliding along metal. All you need to do is tighten these rollers. Take a look at the base of the door and locate the adjuster screw hole. This can be turned using a screwdriver (or Allen key, depending on the door's manufacturer). Tighten the screw, taking care not to chip the door's paint. If you have a type of door that does not have an adjuster screw, a professional will need to do the job for you.