What is ensured by having brake shoes free of grease and oil?

Having brake shoes free of grease and oil significantly contributes to improved grip. When brake shoes are clean and free of contaminants, the friction material can effectively engage with the brake drum or rotor. This engagement is crucial for producing the necessary stopping power. Contaminants like grease and oil can create a slippery surface, which diminishes the friction needed for effective braking, resulting in longer stopping distances and potentially compromising safety. By maintaining clean brake shoes, drivers ensure that their brakes respond promptly and effectively.

The other options might relate to various aspects of brake maintenance and performance, but the primary reason for ensuring that brake shoes remain free from grease and oil is to maintain optimal grip and safety during braking.