Nylon bristles and foam sponges are consumable parts, and they wear down at a rate that depends on how often you clean and how dirty your chain gets. Park Tool's RBS-5 Rebuild Brush Kit replaces all 5 wear components inside the CM-5, CM-5.2, and CM-5.3 Cyclone chain scrubbers, restoring the cleaning chamber to the same condition it shipped in. You get 1 large side scrubbing brush, 2 roller brushes, and 2 wicking foam blocks — the full set of internals that contacts the chain during cleaning.

The large side brush handles the lateral scrubbing action on the outer plates, and the 2 roller brushes rotate against the chain as you backpedal, working solvent into the rollers and inner plates where grit actually accumulates. The wicking foam blocks sit at the exit end of the cleaning chamber and draw excess solvent off the chain before it leaves the unit, which cuts down on drips hitting your floor or workstand. When these foam blocks get saturated with old grime that won't rinse out, they stop absorbing and start redistributing dirty solvent back onto the chain you just scrubbed.

Swapping the parts takes about a minute. You open the Cyclone body, pull out the old brushes and foam blocks, and drop in the new ones. No tools required. If you're also noticing that your cleaning results have declined even with fresh solvent, the brushes are the first thing to check — the roller brushes on the large rotating cylinder tend to wear fastest, especially if you're running wider chains. Replacing all 5 components at once keeps the cleaning performance consistent across the whole chamber rather than having one worn piece bottleneck the system.