the main brush keeps getting tangled with hair and stops spinning every few days.

Diagnosis

The Roborock S8 Pro Ultra utilizes a dual rubber brush system designed to reduce tangles, but it is not immune to "winding." The root cause of the brush stopping is typically the accumulation of long hair and synthetic fibers around the gear-driven ends of the rollers. Because the rollers are rubber, hair doesn't just wrap around the circumference; it migrates inward toward the bearing housings and the drive axle. When hair builds up in these tight gaps, it creates mechanical friction that exceeds the motor's torque limit. The onboard sensors detect this resistance as a "jam," triggering a safety shut-off to prevent the motor from burning out. You can confirm this is the issue if the robot stops mid-cycle and reports "Main brush jammed" in the app, or if you notice a visible "donut" of hair gathered specifically at the very edges of the rubber bristles where they meet the plastic end-caps.

How to Fix It

To fully resolve the jam and prevent frequent stalls, follow this deep-cleaning sequence:

1. Power down the unit and flip the S8 Pro Ultra onto its back on a flat, clean surface.
2. Locate the brush cover release tabs. Firmly press and lift the cover to expose the dual rubber rollers.
3. Lift both rubber rollers out of the brush chamber. Do not pull them violently; lift them straight up.
4. Inspect the ends of the rollers. Use a pair of precision scissors or the dedicated cleaning tool to cut through the hair wrapped around the rubber. Be careful not to slice the rubber bristles themselves.
5. Crucially, pull off the removable plastic end-caps from the rollers. Hair often hides inside these caps, creating a hidden "plug" that causes the rotation to seize. Clear all debris from inside these caps.
6. Reach into the brush chamber (the cavity where the rollers sit). Use a tweezers or a small brush to clear the silver drive axles and the gear sockets. Even a small amount of hair here can prevent the roller from seating properly.
7. Wipe the interior of the chamber with a damp, lint-free cloth to remove fine dust that can act as an abrasive.
8. Reinsert the rollers, ensuring they snap firmly into the drive gears. Replace the cover and run a test cycle.

If That Didn't Work

• Check for "Bearing Failure": If the brush still stops without visible hair, the internal bearings of the roller may have worn out or become clogged with microscopic grit. Replace the rollers with a new set of official Roborock S8 dual-brush replacements (Part No: S8-Main-Brush).
• Inspect the Drive Belt/Motor: If you hear a grinding noise but the brush isn't spinning, the internal drive belt may have slipped or the motor gear may be stripped. This requires a full chassis teardown to inspect the motor assembly.
• Update Firmware: Ensure your robot is on the latest firmware version via the Roborock app. Some early versions of the S8 Pro Ultra had overly sensitive jam detection that triggered "false positives" even with minimal hair.
• Verify Floor Obstructions: Check if the robot is consistently dragging a specific rug edge or cable. If the brush is pushed upward into the chassis by a thick rug, it will trigger a jam error even if the brush is clean.

Heads Up

• Schedule a "Deep Clean" every 14 days. While the rubber brushes are better than bristles, they still require manual intervention to clear the end-caps.
• Avoid using wet cloths to clean the silver drive axles inside the chamber; moisture can lead to premature corrosion or rust on the gear teeth.
• If you have high-shedding pets, consider trimming the hair of your pets more frequently to reduce the load on the vacuum's torque motor.
• Never use lubricants or WD-40 on the brush axles; this will attract more dust and hair, creating a "sludge" that will jam the motor faster than dry hair would.