Replacing pocket door rollers is not too hard if you have the right ones to replace them with. There are some concerns with attempting to replace the rollers.
Pocket Door Rollers - Standards
You might think that something as common as pocket doors, that there would be some standards. Unfortunately, there are not.
See the article 'Issues With Pocket Door Track', for additional information.
How Pocket Door Rollers Work
Pocket door rollers keep the door running inside of a metal track. The rollers are made of metal and nylon and usually have three or four rollers on each assembly. Regular doors are supported by hinges. The hinges are attached to the side of the door. A pocket door has hangers that are attached to the top of the door with metal brackets. Like any wheel that uses bearings, lack of lubrication can cause them to wear out and start to tighten. When this happens the door becomes hard, sometimes impossible, to move.
The door rollers need to be able to ride in the grooves in the track. The track is 'C' shaped with the sides curled up to form a groove. The style of roller usually matches the metal track that they ride in. Finding rollers that are an exact match for the ones that you have may be challenging. You can buy kits that have new track included. The problem is that unfastening and installing the track inside the pocket is pretty hard.
Removing Pocket Door Rollers
The rollers and the track need to match, otherwise, they won't work, or they will work very poorly. So you need to make sure you get the correct ones before you remove the old ones.
See the article 'Removing Pocket Door Rollers' discusses how to take off the door and remove the rollers. You might want to get some help, before you attempt to remove the door.
Most of the time, replacing the rollers is not practical or even possible. Lubrication will usually get them working again. See the article 'Lubricating Pocket Door Rollers' for more information. It could be that a little oil will solve your problem.
Replacing the Rollers
With the door removed it is easy to replace the rollers. There is an opening at the end of the support track on the strike side of the door. Tilt the roller assembly into the opening, moving it into the track until the wheels start to roll in the track. Continue to move the roller toward the middle of the door opening, tilting it until the second set of wheels engages the track. Move it into the track until all the wheels are in the grooves in the track. move the roller back and forth to make sure it is working freely.
Move the first roller toward the far side of the door. Repeat the process with the second roller. Again, check to make sure both rollers are working freely.
Putting the Door Back On
Getting the door back on the hangers is a little tricky. See the article 'Putting a Pocket Door Back on Track' for information and instructions.