1888a123_Beginner_Dirt_Bike___GICL_Wiki_Dirt_Bike_Parts_List_Function
[Part and Quantity] Rear Brake (1) [Part Number] DR70-402 [Materials] Metal, steel for strength [Forces] Frictional forces needed to slow bike [Manufacturing Process] Die-casting [Shape] Circle shape with two "half moon" shaped shoes [Part Complexity] 4 [Function] 
Functional: Presses shoes against brake drum creating friction to stop the bike
Group 11 - Beginner Dirt Bike - GICL Wiki