The active gel works to quickly dissolve heavy brake dust! It turns purple because it dissolves brake dust! Tough on dirt and grime on the road, but not on your wheels! Acid-free and pH balanced — safe for all wheel finishes! Safe on coated brake components! Provides powerful cleaning, yet gentle and safe. Meguiar's® Ultimate All Wheel Cleaner offers our strongest cleaning performance and is also safe for all wheel and brake finishes! This advanced chemistry combines surfactant-destroying road heat and effective agents to dissolve brake dust. The deep cleaning gel formula transforms brake dust into purple and brown, and road grime because it gently loosens stubborn contaminants. And since it is acid-free and pH balanced, this wheel cleaner is safe and effective for all wheel finishes and coated brake components.