1. First of all, in order to keep the steering wheel held by the driver in the center automatically, and to reduce the driver's fatigue, it is necessary to tilt the spindle backward. This is just like the front fork of a bicycle leaning backwards, which can make your hands relaxed.
2. However, after the main shaft is tilted backward, the front wheel will swing slightly at high speed, which will make the body unstable. In order to overcome the small swing of the front wheel, it is necessary to turn the kingpin outward. The slower the speed and the more uneven the road, the greater the angle of the kingpin outward, such as a four-wheeled tractor. As the two front wheels camber in opposite directions, the small swing of the front wheels is offset each other, and the car body is more stable.
3. However, it comes with the following: because the kingpin leans outward, the front wheel also leans outward, so the front wheel has a tendency to turn outward, that is, the left front wheel turns left, the right front wheel turns right, and the front wheel is installed on the car, so it can't turn, which causes serious tire wear. The toe-in is to solve this wear problem. The wheels on both sides are left at an angle inward, which just offsets the tire deviation caused by the camber of the kingpin, so that the tire can move forward in a straight line, so that there is no dry grinding phenomenon, thus achieving the purpose of reducing tire wear.
This is the origin of toe-in, which originally started with reducing the driver's labor intensity and evolved from one ring to another. Spindle backward tilt-kingpin outward tilt-toe-in, one ring is buckled.