Which of the following is NOT a tire wearing angle?

Caster is a pivotal angle affecting steering dynamics and vehicle stability, but it is not classified as a tire wearing angle. Instead, caster refers to the angle formed between the steering pivot points (upper and lower ball joints) and a vertical line when viewed from the side of the vehicle. It influences the self-centering of the steering and the stability of the vehicle during straight-line travel.

On the other hand, camber and toe are directly related to tire wear. Camber describes the inward or outward tilt of the wheels when viewed from the front, impacting the contact surface area of the tire on the road. An incorrect camber angle can lead to uneven tire wear. Similarly, toe measures the angle at which the tires point towards or away from each other when viewed from above. Like camber, improper toe settings can result in excessive or uneven tire wear.

The term "spherical angle" does not pertain to standard alignment measurements associated with tire wear. Instead, it might refer to other concepts in geometry or mechanics. Since caster does not contribute to the angles that lead to tire wear, it is identified as the correct answer in this question.