Find where the rub starts before changing anything. A rub that appears at one point of the door's travel is a contact event - debris under a wheel, a high spot on the track, or a stop that is set early - while a rub that runs along the whole edge points at height, alignment or a panel that has dropped. The two have different fixes, and the position of the rub is what separates them.
Owners usually notice the symptom rather than its position: the door "catches", the sweep "drags", the bottom edge "scrapes". None of those descriptions locate the fault, and adjusting the door to cure a rub that was caused by debris moves the door away from a setting that was correct.
Rub Location as the First Diagnostic Signal
The first step is to make the rub repeatable. Move the door slowly by hand and listen for the point where the sound or the resistance begins; then mark the position on the track or threshold with a piece of tape and run the door again. A rub that starts at exactly the same place every time is a contact, and a contact has a physical position to examine.
Reading the position is then a matter of matching it to what is underneath.
| Where the rub appears | What it usually means | What to check first |
|---|---|---|
| At one end of the travel | A stop, an end cap or a build-up of debris where the door parks | The end of the track and the door's parked position |
| At the same point in the middle | A step or high spot in the running surface | The track surface along the line the wheel uses |
| Along the whole length | The panel sits too low, or the bottom edge is no longer parallel | Panel height and how the sweep meets the threshold |
| Only when the door is pushed or pulled | Movement in a fixing or in the panel itself | The fixings and the panel's line, not the sweep |
A rub is a contact, and every contact has a position; the position is the diagnosis. That sentence is worth carrying into the next step, because it decides whether the work belongs to the track, the panel or the fixings.
Height versus debris as the cause
Once the position is known, the cause is usually one of two families, and they are told apart by what changes the rub.
Height and alignment problems
A panel that sits too low will rub along the whole edge, because the sweep is being pressed onto the surface it is supposed to wipe. The same symptom appears when the panel is not parallel to the threshold, which happens after one roller is adjusted differently from the other or after a fixing has moved. Height problems are proportional: the rub gets worse as the door moves further from its correct position, and it does not depend on the surface being dirty.
Debris and surface problems
Debris produces a rub that is local. Grit or hardened residue on the running surface lifts the wheel as it passes, which tips the panel and makes the bottom edge touch at one point. A step or a dent in the track does the same thing permanently. Debris problems are positional: the rub appears where the obstruction is, and cleaning or smoothing that spot removes it.
Two tests separate the families quickly. Clean the running surface and the bottom edge, then run the door again: if the rub has gone or moved, debris was involved. And check the gap between the sweep and the threshold at both ends of the panel: if it differs, the panel is not sitting parallel, which is a height or alignment fault rather than a surface one.
Cleaning Before Any Adjustment
Cleaning comes first because it removes the possibility you cannot see. A track that has collected grit, or a bottom edge with soap residue dried onto it, produces a rub that looks exactly like a mechanical fault until the surface is clean.
The cleaning that matters is specific. The running line the wheel travels on, the ends of the run where material collects, and the length of the bottom edge where the sweep meets the threshold. Wiping the visible face of the track is not the same as clearing the line the wheel uses, and hardened residue needs to be removed rather than wetted.
After cleaning, run the door twice and compare the two results. A rub that has gone confirms debris. A rub that remains in the same place, with the surfaces clean, points at the other family - and that is the point at which adjustment becomes the right tool rather than a guess.
What Adjustment Can and Cannot Change
Adjustment changes where the panel sits, not what it is made of. That distinction decides whether adjustment is the answer or merely the next step.
- Adjustment can raise or lower the panel so that a sweep meets the threshold evenly along its length rather than pressing at one end.
- Adjustment can correct the panel's line where one side has drifted, which is the most common cause of a rub that appears along the whole edge.
- Adjustment cannot remove debris, so a local rub caused by grit will keep returning until the surface is cleaned.
- Adjustment cannot repair a damaged track, and raising a panel to clear a dent hides the fault while changing where the door runs.
- Adjustment cannot correct a fixing that is moving; the door will drift back, and the same rub will return within days.
Two signals say that adjustment has done its job and something else is the limit: the rub returns in the same place after the door has been left alone for a week, or the door stops rubbing but starts to run unevenly or leak along an edge, which means the geometry was changed rather than corrected.
Clean the running surface, compare the gap at both ends of the panel, then test the door again. A rub that has gone was caused by the surface; a rub that returns in the same place with the surfaces clean points at the panel's position or its fixings.