What is a belt molding on a car door?
Reviewed by the Skyview Auto Glass technical team — NWRD-, ASE- and DINITROL-trained technicians · Updated November 2026
Quick answer
A belt molding, also called a window sweep, is the rubber strip that runs along the bottom of a door window where the glass enters the door. There is one on the outside and one on the inside. Each wipes water and grit off the glass as it moves; worn sweeps let both into the door, which leads to scratches and corrosion.
What is a window sweep?
The belt molding is the horizontal rubber strip along the top edge of the door, right where the window glass disappears inside. Look closely and there are two strips: an outer sweep that faces the weather and an inner sweep that faces the cabin. The glass passes between them every time it moves, and the lips of both strips wipe the pane clean on the way.
The name belt molding comes from the belt line, the horizontal crease that runs around the vehicle where the glass meets the sheet metal. Along that line the sweeps are the door’s first defense. They keep rain from simply pouring into the door on every downpour, they block wind at speed, and they squeegee grit off the pane so it is not dragged into the door.
Worn sweeps fail quietly. The lips flatten and stiffen with age until they no longer hug the glass, and then two things follow. Water runs into the door cavity and pools against the inner metal, and grit that should have been wiped off rides down into the door, where it scratches the glass on every later movement. A scratch line low on the pane is often the giveaway.
How to tell the sweeps are worn
- A horizontal scratch line near the bottom of the window
- Grit has lodged in a hardened sweep lip and is being dragged across the pane on every raise and lower.
- Water inside the door after rain or a wash
- The outer sweep no longer wipes or seals, so water runs past it into the door cavity.
- Wind whistle at speed from the window line
- The flattened lips leave a gap along the belt line that air can enter.
- A rattling or flapping strip along the door top
- The sweep has shrunk or come loose from its channel and is moving in the airstream.
What worn sweeps cost you down the line
- Scratched glass that only a pane replacement fixes, since deep scratches do not polish out.
- Water in the door that corrodes the regulator, motor mounts, and wiring inside.
- Faster wear on the run channels the glass travels in.
- Cabin noise at highway speed from the unsealed belt line.
- Fogging or mineral lines on the inside face of the glass where water wicks up.
Why is my window scratching?
A repeating scratch low on the pane almost always means grit is trapped in a worn sweep. Replacing door glass runs $180 to $400, so having the sweeps checked stops a small strip from costing a pane.
More questions about belt moldings
What is the rubber strip at the bottom of a car window?
It is the belt molding, or window sweep. There is an outer strip and an inner strip, and the glass passes between them, wiping water and grit off the pane each time it moves.
Do the sweeps get replaced when the glass is replaced?
It is the sensible moment to do it. The door is already opened up for the pane, and fitting fresh sweeps protects the new glass from the grit that scratched the old one. A shop can assess the strips when quoting the glass.
Can I clean the sweeps instead of replacing them?
Cleaning helps when the strips are sound but loaded with grit: wipe the lips with a damp cloth and pick out debris. Cleaning does nothing for lips that have flattened or hardened with age, which is the usual failure.
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