Brush and side-brush replacement: when and how
Brushes are the robot vacuum's tires: consumables that wear out and, when worn, silently make the whole machine worse. Weak pickup along baseboards, dust lines down the middle of the carpet, and the robot seeming to "push" debris instead of collecting it are all brush wear. The fix costs little and takes minutes — once you know what to look for.
Signs the brushes are worn
For the main brush, look for bristles that are bent, splayed, or visibly shorter on one side; rubber beaters with nicks, chunks missing, or a glossy polished surface instead of texture. For side brushes, the tell is splayed arms: the thin arms should sweep outward and spring back, but with age they permanently curl or snap off. Any missing or broken side-brush arms mean corners and edges stop getting swept. A practical rule: if you've owned the robot a year of regular use and never replaced the brushes, they're almost certainly past their best, even if they look okay.
What to buy
Buy replacements matched to your robot's brand and model — brush dimensions and mounting shapes differ between manufacturers, and this is the one part where "close enough" genuinely matters because the brush has to seat into the drive socket. Check whether your robot uses bristle, rubber, or combo main brushes: replacing like-for-like keeps performance predictable. Keep the old brush until the new one is installed and working, in case of a fit problem.
Replacing the main brush
Power the robot off and flip it over. The main brush sits in a channel across the middle of the underside, usually held by a brush guard or cover secured with tabs or small screws. Release the guard, lift out the old brush (note which way it sits — the drive end usually has a shaped socket), and set the new brush in the same orientation. The brush should spin freely in the channel with no rubbing. Refit the guard and confirm it clicks or sits flush. On many models the whole job needs no tools at all; where screws are involved, a small Phillips screwdriver is usually enough.
Replacing the side brushes
Side brushes are the small spinning arms at the front corners that sweep debris into the main brush's path. They typically pull or twist off their spindle — check for a small screw on some models. The key detail: side brushes often have a colored dot or an L/R marking matching a dot on the spindle, so each arm's bristles sweep in the right direction. Mount the wrong side and the brush throws debris away from the intake instead of into it. After fitting, spin each side brush by hand to confirm it rotates without wobbling.
Cleaning between replacements
You can extend brush life a lot with regular cleaning. Once a week, remove the main brush and pull off wrapped hair and thread — a seam ripper or scissors slid along the brush make this easy, and pay attention to the ends, where hair wraps around the bearings and creates drag. Clear debris from the side-brush spindles too. Brushes that spin freely draw less current, which also reduces strain on the drive motors and battery. Never oil or grease the brush ends; it attracts dust and makes the wrap worse.
A maintenance cadence that works
A simple schedule: weekly brush cleaning (hair removal), monthly side-brush inspection (look for splayed or broken arms), and brush replacement roughly every 6–12 months for the main brush and every 3–6 months for side brushes with daily use. Pets, long hair in the household, and heavy shedding seasons push you toward the short end. Keep one spare set on the shelf so a worn brush is a five-minute swap instead of a week of degraded cleaning while you wait for delivery. Your robot's app may track brush hours and nag you at thresholds — those estimates are a decent starting point, but your eyes and the cleaning results are the real gauge.