This is due to the rotation rate of the structural elements of the wheels being just above the flicker fusion threshold frequency, around 60 Hz [1]. As the whee

This is due to the rotation rate of the structural elements of the wheels being just above the flicker fusion threshold frequency, around 60 Hz [1]. As the wheels spin faster, they just look like a blur. [1] https://en.m.wikipedia.org/wiki/Flicker_fusion_threshold https://en.m.wikipedia.org/wiki/Flicker_fusion_threshold