Mechanically speaking, what happens when a cars alignment is off? Why is it designed to misalign to begin with?
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Your suspension moves and is subject to wear and tear over time. Then there’s minor damage from from hitting bumps, road debris and rubbing against curbs. Making it adjustable helps to extend the cars life because it can be corrected easily and for cheap.
As to how it effects the car, that’s a bit more complicated. There are three main angles. Caster, camber, and toe. Camber is how the tire leans in or out. Like how lowered or stanced cars have the tires leaned in to tuck up under the fenders, that’s camber. Toe is how the tires are turned in or out, like if you point your feet together or away from each other. Caster is how the two pivot points of the wheel are in relationship to each other. This one is harder to understand, but it’s the same as the rake of motorcycles front forks. It makes the car stable at high speeds. If you think about your bicycle, Caster is why the bike was hard to control when you spun the handle bars so the front wheel is backwards, you changed the Caster to a negative value.
Now toe can help the car drive straight easier. If they are a little pigion footed, the car won’t chase ruts in the road as bad. But if it’s too far away from straight ahead, it will scrub the tires down fast. Kind of like dragging a ball over concrete instead of rolling it. Toe is also what makes the steering wheel center. So if it’s a little crooked, then the toe set even from side to side.
Camber makes the car more stable around corners if it’s slightly leaned inward towards the car. More is not always better here, so too much inward camber makes the car less stable all around. If you have too much inward camber the inside edge of the tire will wear to nothing while the rest of the tire has normal tread. This is due to how the weight of the car is spread across the tire. If it’s too far in that weight is more on the inside and if it’s too far leaned out, the tires outside edge will wear instead. Camber is really a balancing act of handeling and tire wear.
Caster is the only one of these that won’t affect tire wear. Since it’s just a relationship of the two pivot points that allow the front wheels to turn, it doesn’t have any affect on how the tire meets the road. But it is a big performance enhancer. The more rake in that relationship the more stable the car is at speed. If a cop was trying to do the PIT maneuver on your car, Caster is going to make it easy or hard for them. Economy cars are easy to PIT because they have less Caster, like 1-3 degrees. Sport luxury cars like Mercedes have anywhere from 6 to 9 degrees of Caster making them much harder to PIT and it’s what makes them easy to handle at autobahn speeds. There are videos of police chases where they PIT a benz, and their pretty interesting as they often have to pivot the benz around their own car after several hits because they always straighten out pretty easily.
There is a whole lot more than this, but these are the basics of the three angles you will see on a standard alignment.
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