How do I fix a sliding or bifold door that jumps its track?

Sliding and bifold doors fail in a small number of ways, and the cheapest cause is by far the most common. Working in order stops people replacing a mechanism that only needed cleaning.

Safety

Step by step

1. Clean the track thoroughly first.Vacuum it, then a stiff brush and a damp cloth into the channel. Dust, grit and hair pack into the bottom track and are the most common cause of a door jumping, sticking or running roughly.
2. Look along the track for damage.Kneel and sight down it. A bent lip, a dent, or a section that has lifted from the floor will throw the door every time it passes that point — which is the tell, since the fault happens at the same place.
3. Straighten a bent track carefully.Pliers with tape on the jaws, or a block of wood and light taps. Aluminium tracks bend back reasonably well; steel ones often need replacing.
4. Check the rollers.Lift or unhook the door and look. Flat spots, cracks, seized bearings or a wheel that will not spin freely. Rollers are the usual mechanical failure and are inexpensive replacements.
5. Find the adjustment screws.Most sliding and bifold doors have height adjustment at the bottom of each door, sometimes behind a small cap. Turning them raises or lowers that corner, which is how a door out of alignment is corrected.
6. Adjust one corner at a time.Small turns, testing between each. Adjusting both ends at once means losing track of what changed, and the doors have to end up parallel to each other as well as level.
7. Check the top guides on a bottom-rolling door.A plastic guide at the top keeps the door from swinging out. Broken or missing guides are a common cause of a door leaving its track, and they cost very little.
8. Check the pivots on a bifold.Bifolds hang on a top pivot and a bottom pivot, with a guide pin in the track. Worn pivots let the door drop, and the pin then rides out of the channel.
9. Make sure the track is level and firmly fixed.A loose fixing lets the track flex under the door's weight. Check every screw, and add fixings if the track spans a long run unsupported.
10. Lubricate correctly.Silicone spray or dry PTFE on the track and rollers. Not oil or grease, which collects dust and makes the problem worse within weeks.
11. Check the doors are not out of square.A wardrobe carcass that has racked will throw the doors regardless of what you do to the track. Measure the diagonals of the opening.
12. Replace the roller assembly rather than the door.Roller sets are widely available for common systems and are usually the whole fix. Take the old one out and match it, or find the system's model number on the track.

Tips

• Note where along the run it jumps. A fault at the same point every time is the track; a fault anywhere is the rollers or the adjustment.
• Silicone or dry PTFE, never oil. Oil on a track collects dust into a paste and the door runs worse than before.
• Photograph the roller assembly before removing it. Matching a replacement is much easier with a picture and a measurement.

Common mistakes

• Oiling the track — Oil collects dust and grit into a paste that makes the door run worse within weeks. Use silicone spray or dry PTFE.
• Adjusting both ends of a door at once — You lose track of what changed and the doors have to be parallel to each other as well as level. One corner at a time, testing between.

If it doesn't work

Questions people ask