Which brake system of a motor vehicle functions without any appreciable wear?

The engine brake and the retarder are two systems that can slow down a vehicle without significant wear on the braking components. The engine brake uses the engine's resistance to reduce speed, while the retarder helps slow down large vehicles like trucks by creating resistance through hydraulic or electric means.

In German traffic regulations, these systems are important for safety and efficiency, as they help maintain control of the vehicle while reducing wear on traditional brake systems. Understanding their functionality is essential for drivers, especially in managing vehicle speed, particularly on slopes or during long descents.

The compressed air-braking system, while effective, does have wear associated with friction, so it is not included in this specific answer. Recognizing the correct combination is critical for ensuring that drivers can make informed decisions on vehicle operations under various conditions.