The alignment of your wheels plays a much larger role in car performance and handling than most people give it credit for. In short, while the basic positioning of each wheel is dictated by the various arms, driveshafts, and other parts of the suspension, the attitude of the wheel is adjustable by a few degrees. While a change of only 1 or 2 degrees may seem petty, at high speeds and/or at the limit, those couple of degrees can be the difference between solid handling and a terrifying car.

There are 3 possible adjustments that can be made to align a wheel: toe, camber, and caster (for the front wheels only). Whether any of these three are actually adjustable on any given model of car depends on whether the manufacturer designed the car to have those adjustments. Virtually every car has toe adjustments, most have camber adjustments, and only some have caster adjustments, as a general rule. Your alignment shop should know what is adjustable on your car, as they usually will consult some mechanics’ manual that will explain what is adjustable on your car and how to do it. But, that doesn’t mean they will get it right, necessarily.

Toe
Toe is the most basic and, arguably, most important alignment setting. Toe is the horizontal angle of the wheel, ie, whether the front tip of the tire points towards or away from the car. Imagining walking with your toes pointed in - when your tires are pointing the same way, that is called toe in. The reverse is called toe out.

What does Toe dictate?
The short answer is that Toe dictates how “willing” a tire is to steer the car. Toe in makes a car less willing to steer, and thus makes the car more stable at speed. So, if you have toe in on your front tires, the car will feel more stable at speed. If you have toe out on your front tires, the car will be more “jumpy” and will respond faster to steering inputs, albeit at the expense of stability (as the steering is just that much more sensitive).

In the rear, toe in makes the rear more stable. Toe out in the rear generally makes cars more prone to enter wild and difficult-to-control oversteer. But, different cars respond differently to rear toe.

Toe and Tire Wear
The least amount of tire wear will occur when there is ZERO toe - that is, the tire is pointing DIRECTLY ahead. Any amount of toe in or toe out will cause more wear, as you are literally pushing the tire along to a certain degree. Toe out tends to cause more wear than toe in, but mild toe out will wear less than very aggressive toe in, as a general rule.

Camber
Camber is the vertical angle of the wheels, ie, whether the top of the wheel points towards or away from car. When the top of the wheel points towards the car, this is known as “negative camber.” When it points away from the car, it is known as “positive camber.”

What does Camber dictate?
Camber affects how much of the contact patch will actually touch the road while cornering. As a car corners harder, the lateral acceleration causes the car to roll in the opposite direction of the turn. I.e., the harder you turn to the right, the more your car will lean to the left. As your car leans more towards the left, the tire likewise will lean to the left. That means that as your corner harder, the contact patch shifts to the outside of the tire.

So what does that mean? A tire performs optimally and produces maximum grip when the tread is planted as squarely as possible on the road. The reason for that is quite simple: as the tire leans in or out, the contact patch moves from the tread itself to the sidewall. And the sidewall is designed to support the tread, not be in direct contact with the road.

So, lets say you have 0 degrees of camber (your wheel is perfectly perpendicular to the road). As you corner harder and harder, you are literally riding on more and more of the sidewall of your outside wheels (your left wheels if we continue the example above where you turn to the right). This actually reduces the amount of grip availble, as the sidewall does not offer as much performance and grip as the tread itself, and less of the inside tread will be in contact with the road.

So why wouldn’t you just run as much camber as possible? Tire wear is the answer, which brings us to our next section.

Camber and Tire Wear
Tire wear involving camber is a function of how much camber you have and how hard and how often you corner. More negative camber means that you are literally riding on the inside of the tire while traveling in a straight line. If all you do is highway driving and you run lots of negative camber, you will wear the inside of the tire MUCH faster than the outside of the tire, using up the tire prematurely. At the other extreme, if your fully race-prepped Spec Miata with R Compound racing tires has 0 degrees of camber, you will be riding on the outside/sidwall of the tire in every corner, which is most of the time. Your will wear the outside MUCH faster than the inside, and will wear the tire out prematurely.

Lowering a Car Usually Yields More Camber
As a general rule, lowering a car also produces more negative camber. The amount it introduces depends on a number of variables, including the type of suspension the car has and even the minute differences between each specific car’s chassis. Cars with McPherson struts (which are on most cars) tend to yield more negative camber as the car is lowered, by virtue of the design. Cars with double-wishbone suspension tend to do so somewhat less.

Camber Plates
Oftentimes on race or performance-oriented cars, the factory setup will not allow as much camber as the owner desires. One popular solution to this problem is to install camber plates. Designs vary, but the plate bolts to some part of the strut assembly, and allows for a greater range of camber adjustments (usually more negative camber) than the stock setup.

Caster
The final part of an alignment is caster. Caster is the angle of the front struts. Think of it this way: you know how the front fork on a bicycle comes back at an angle? That angle is caster. The same applies to the front struts of cars.

Most cars do not have adjustable caster; it is usually predetermined at the factory, and there isn’t much one can do about it.

What does Caster dictate?
Caster determines how easy or difficult it is to turn the steering wheel. As the angle of the front struts increases, the front wheels “want” to return to the straight-ahead position more. As such, the effort required to keep the wheels turned increases as the angle of caster increases.

Increased caster also creates more negative camber for the outside wheel the more the wheels are turned. I.e., if you have a lot of caster, you will get increasing negative camber on your right front wheel as you turn the steering wheel more to the left. For the most part, though, this phenomenon is a non-issue at speed. On very low speed courses with extremely tight corners, you may notice a difference in grip in theory with increased caster as it requires a lot of steering input. But probably not.

Caster really is used to fine-tune the steering feel of the car. With power steering, this is usually a non-issue, but it can become more important if you have manual steering (or particularly if you remove your power steering). Of the 3 aspects of alignment, caster is the least important. It will only affect steering effort, and has virtually no impact on actual performance.

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