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As mentioned before, it is impossible and hopeless to keep the thrust angle at Zero degree by measurement and adjustment.
The captain of a light airplane that does not have an automatic device by a computer, adjusts his trim according to his own feeling, and in the case of an airplane that flies horizontally, the opponent is air and must be balanced three-dimensionally. On the other hand, in the case of vehicles, it is friction with the road surface with slipping resistor and is balanced on a two-dimensional plane.
To be honest, I took a sneak peek at the measurement and adjustment of the thrust while considering them, and when I actually went into the scenery, there were many uncertainties, and I had an incredibly furious difficulty in the working. And it was not something that an outsider amateur could do, far from reality!
As a result of more than 20 years of insistent and repeated trial and error, I have experienced more than 10 different cars while that time and finally came close to be able to do something like that recently.
When measured several hours after the start of the measurement, I also took several years to figure out why the data was deviated so much, but this was mainly due to spot deformation of the tires parked in a place for long period of time. I learned that this effect could be dealt with by increasing the tire pressure for convenience.
Even if the thrust angle is brought to zero at that moment from the state where it exists, he has all kinds of bushes, including the release of pressure displacement and the change and wear of the tire ground surfaces, and other fluctuations occur, which cannot be achieved only by one measurement and adjustment.
It's a barren world that has to be repeated endlessly.

All industrial machine products are made while allowing a certain error. There is a tolerance for each component machine element, and there is an assembly error in which errors are accumulated as a result of assembly. This latter error is a variation of the product and is set as a tolerance value. The smaller the tolerance value is, the higher the precision of the machine will be, and the higher the cost will be. This tolerance is stipulated in detail in the JIS standard as a machine element.
An automobile can be regarded as an industrial product that combines many mechanical elements, but it is employed many rubber parts for tires, axle arm connections and engine support parts for the purpose of vibration and sound insulation.
As for the rubber material used, often used NBR, IIR, etc., but it is inevitable that it will be deformed and deteriorated due to aging and continuous pressurization.
In addition, there are physical characteristics peculiar to rubber, which makes it difficult to adjust and maintain the desired value of the axle.
Among the characteristics, viscoelasticity and pressure displacement and the hysteresis characteristics associated with them, the displacement quickly recovers when the external force is removed. However, there is some residual strain, and it takes time to recover as it's original figure. It shows two-step or several-steps deformation recovery characteristics.
In addition to the product variation due to the assembly tolerance as a machine mentioned above, the existence of many built-in rubber parts makes it difficult to measure and adjust the wheel alignment of an automobile and maintain the set state.