my vacuum is making a horrible grinding noise only when it's on carpet, sounds like it's eating something

Diagnosis

The grinding noise you hear specifically on carpets is caused by a "bearing jam" at the ends of the main rubber brush roll. While the brush may seem to spin freely in the air, the increased resistance and friction created when the brush is pressed into carpet fibers force the motor to work harder. This pressure pushes the brush roll slightly off-axis, causing debris—specifically long hair, synthetic carpet fibers, and pet fur—that has wound tightly around the axle ends to compress and grind against the motor housing and plastic drive gears. This is not a motor failure, but a mechanical obstruction. When the brush is on a hard floor, there is less downward pressure, allowing the brush to spin despite the debris. On carpet, the brush is pushed upward into the chassis, squeezing the accumulated "hair rings" against the bearing caps. To confirm this, flip the robot over and try to spin the brush roll by hand; if you feel a "crunchy" sensation or see thick bands of hair wrapped around the very edges of the brush where it meets the plastic end-caps, you have found the source of the noise.

How to Fix It

1. Power down the Roborock Q Revo MaxV completely using the power button on the chassis to prevent accidental activation during cleaning.
2. Flip the robot onto its back on a clean, flat surface.
3. Locate the main brush cover. Press the two release tabs on the sides of the brush guard and lift the cover away from the chassis.
4. Grasp the main brush roll and lift it straight out of the housing.
5. Remove the plastic end-caps from the brush roll. These caps snap off; pull them firmly to expose the metal axle.
6. Use a pair of sharp precision scissors or a seam ripper to cut through the hair and string wound around the brush. Do not just pull the hair, as this tightens the knot; cut vertically along the length of the brush.
7. Focus specifically on the edges. Use a toothpick or a small screwdriver to scrape out the compacted debris trapped inside the grooves of the end-caps and the interior of the brush housing.
8. Inspect the drive gear (the small gear on the robot's chassis) for any trapped pebbles or debris that may have entered the housing.
9. Reinstall the end-caps, slide the brush back into the housing ensuring it seats fully into the drive gear, and snap the cover back into place.

If That Didn't Work

• Inspect the Side Brush Gearbox: If the noise persists, the side-spinning brush may be the culprit. Remove the two screws holding the side brush in place and check if hair has wound itself around the gear shaft underneath the brush head. This often creates a high-pitched grinding sound that mimics the main brush.
• Check for Foreign Objects in the Intake: Use a flashlight to look inside the vacuum intake port. A small pebble or a piece of hard plastic (like a Lego) can get lodged between the brush and the chassis. On carpets, the brush pushes these objects against the plastic wall, creating a loud rattling or grinding sound.
• Replace the Main Brush Roll: If the brush roll has been used for over 6 months, the rubber fins may be worn or the internal axle may be warped. Replace the brush with a genuine Roborock replacement part to ensure the tolerances are correct.
• Verify Wheel Bearings: While the noise is usually the brush, check the main drive wheels. Press down on the wheels; if they "click" or grind, a small stone may be lodged in the wheel tread or the internal bearing may have failed.

Heads Up

• Weekly Maintenance: To prevent this, remove the main brush and pop off the end-caps once a week. Hair accumulates in the "hidden" areas behind the caps, which is where the grinding noise originates.
• Avoid Wet Debris: Never vacuum up damp carpets. Wet hair and fibers create a "paste" that hardens around the bearings, making them significantly harder to remove and potentially damaging the motor.
• Check Brush Alignment: When reinstalling the brush, ensure the brush is pushed all the way in. If it is slightly offset, it will rub against the plastic housing, creating a loud scraping noise.
• Clear the Dock: Ensure the dock's cleaning brushes are also clear of debris, as the robot can pick up loose hair from the dock and carry it straight into the main brush bearings.