How does the tracking on the car get hit 'out'

Question

As per the title. If the tracking on a car is adjusted by adjusting the threaded part on the track rod end, how exactly does the tracking go 'out' of alignment over time, and/or how does hitting a kerb or a pothole cause the alignment to shift ???

Everything seems to be rigid, so is it a case of something bending slightly. If the tracking is adjusted using a threaded rod on the track rod end, how does hitting a kerb or a pothole seem to move this adjustment around ??

Answer 1

The alignment goes out after a hit due to bending of components. There are three main things that are looked at during an alignment, and a couple of secondary measurements. I will only discuss the main three, which are camber, caster, and toe. The toe and camber are usually the ones that are adjusted when you get your alignment, as the caster is normally set by the vehicle manufacturer. Caster allows for assistance in turning, as it returns the wheel to a centered position. Camber allows for the tires to be placed flat on the ground during a turn, assisting the vehicle while turning. Toe assist in your steering, as it determines which direction the vehicle travels in relation to a straight center line.
When your alignment is off, it is usually caused by your camber, and toe. These two measurements are normally controlled by your suspension (struts, or mounts) and the tie rods (thin metal screw rods). As we all know roads are not the greatest in most areas of the world, so as the vehicle is traveling, under constant vibrations, it will make some of this parts come loose. This allows them to move around, and slowly come out of alignment. Also, air in your tires is a big factor in your alignment, so if your vehicle is aligned with flat tires, it will be a horrible drive when you air them up.
Lastly, as Brian mentioned, wear on the joints will give the suspension movement that contributes to the misalignment of your vehicle. This can either be caused by slow bending of components, or the extra play accelerates the loosening process of the nuts holding all those components in place.

Answer 2

I'm guessing it's mostly due to wear on various joints that control the exact angle of the suspension. Doesn't take much wear on a joint all the way at the end of an arm to cause a measurable angular change on the other end. Obviously a severe curb hit will cause bending to knock the alignment out too...

I've found that, barring curb hits, it's not much of an issue anymore. I've given up on the regular scheduled alignment checks as it never moves on my car. I now just get the alignment done when work is performed that would cause a change to it. I would of course also get it done if I observed a handling or wear issue developing.