The term 'bike wheel radius' refers to the distance between the center of a bicycle wheel and its outer edge. This is measured in millimeters and is typically between 500 and 600 mm. The term can also be referred to as 'SPOKE, ' which is a five-letter word. Spokes are the thin metal rods that connect the hub of the wheel to the rim, and they help to support the weight of the rider and provide stability. The number of spokes on a wheel can vary, but most modern bikes have between 28 and 36 spokes.