Awesome Answers about an Alignment

toe
The alignment of your car is super important. It has everything to do with how the car handles. You could have a perfect suspension set up, but with a crappy alignment there would be all kinds of handling problems. There are three main terms used to describe an alignment: toe, camber, and caster.
Toe, also known as tracking, is the symmetric angle that each wheel makes with the longitudinal axis of the vehicle, as a function of static geometry, and kinematic and compliant effects.” That’s the definition according to Wikipedia, and hopefully this picture will explain a little better.
toe
“Camber angle is the angle made by the wheels of a vehicle. It is used in the design of steering and suspension. If the top of the wheel is farther out than the bottom, it is called positive camber; if the bottom of the wheel is farther out than the top, it is called negative camber.”  Here’s another picture for you visual learners out there. Everyone has seen camber, even if they didn’t know the name.
camber
Here is camber taken way to far.
camber yuck
Here is an example of perfection.
camber yum
Caster angle is the angular displacement from the vertical axis of the suspension of a steered wheel in a car that is measured in the longitudinal direction. It is the angle between the pivot line (in a car an imaginary line that runs through the center of the upper ball joint to the center of the lower ball joint) and vertical.” Once again, a Wikipedia definition for those that like words, but here is a picture to visualize.
 best caster pic
Can you see the extreme caster angle on this bike?
caster bike
Now that we know the three big components in an alignment, let’s talk about how they can attribute to a car and its handling capabilities. There are three main ways a car can travel around a corner: using understeer, using oversteer, or properly using all available traction.
Understeer is when, in a corner, the front tires break traction and begin to slide so you are turning the wheel but the car is going straight. If you’ve ever seen the movie Cars, just picture the scene were Lightning McQueen is trying to make a hard turn on a dirt race track but keeps sliding forward in a straight path.
understeer vs oversteer
Oversteer occurs when the back tires go over the steering angle of attack and begin sliding out, and if the sliding is not controlled it can cause the car to spin. Everyone commonly knows this as drifting.

drift legacy

Cars have two wheels for turning and two wheels for tracking. In a four wheel drive car, the front tires are tasked with both turning and accelerating. This means that while accelerating and turning, the front tires have more work to do and will lose traction first.

One issue with the layout of a vehicle can be the weight distribution. On top of asking the front tires to both accelerate the vehicle and steer, you’ve gone and put more weight on them. Guess where that leads.

Some say that rear wheel drive cars are the ultimate driver’s car due to their unmatched capabilities. Their weight distribution is better, and if we talk about the corvette which has the transmission as the rear axle, you can find perfect distribution. Since there is not any power being sent to the front wheels, they can focus completely on steering and there is no torque steer (where power being sent through the front wheels pulls the steering wheel to the smaller drive axle). When a rear wheel drive car accelerates, it transfers the weight of the car to the rear wheels which helps it along it’s path. Although when accelerating out of a corner, the weight being sent to the rear of the vehicle can create some understeer due to the weight leaving the the front tires. This is where it all comes down to a finely tuned suspension.

Now we come to the alignment and suspension geometry. When the suspension moves, the alignment changes. This can be helpful with proper suspension design, but a lot of suspension set ups are designed for easy packaging and assembly line. A tire creates the most grip when the entire tread is in contact with the road. So driving along in a straight line or braking, we want the tire to be standing straight up with the tread flat on the ground for even tire wear and optimum braking traction. However, if we set the camber to 0, that ideal contact goes out the window as soon as the steering wheel is turned. When you go around a corner with the stock car, the car leans over, the tire leans over, and you end up doing most of the cornering with the outside edge of the tire and the sidewall. Obviously the sidewall is not supposed to be in contact with the road and that’s not good for grip. We also have to think about when the suspension compresses past a certain point, the tire will actually start to lean outwards which makes the problem even worse.

On top of these handling disadvantages, Most stock cars are setup to understeer at the limit. This is because it’s generally safer to go off the road straight than it is backwards/sideways, and inexperienced drivers tend to have trouble dealing with oversteer. There’s also something called lift-throttle oversteer, and it’s a common cause for crashed WRX’s

One part of the solution is the alignment. Start with the tire leaned in (negative camber) and when the car leans, the tire ends up with more tread contact. This is especially important in the front, where we have more weight and more load in a corner. More negative camber in the front means more grip while cornering and less understeer. How much camber you should have depends on the use of the car and the tires among other things. A pure racetrack or auto-x only car will often have at least -3 degrees (stock is 0 to -1) along with stiff suspension and low profile tires that flex less. On a street car that mostly gets driven in a straight line and never sees high cornering loads this would not be a good thing and you would see uneven tire wear. You can still get away with quite a bit though, and I daily drive with -1.5 degrees of front camber and the tires look pretty good. I’d suggest anywhere in the -1 to -2 degree range for the average road car. It’s also important to have the toe set to 0 or slightly in, if you set toe in you will achieve better turn in response at the sacrifice of higher speed stability. Rotate tires frequently, and make sure all of your suspension and steering components are in good condition.

 

2 thoughts on “Awesome Answers about an Alignment

  1. Sweet post! So if you have been driving on a chamber to the point where the tread has worn down so it’s flat Keith the road now, how does this affect handling even though you still have more chamber? Like does the inside tread begin lifting up like you had no chamber?

    1. Just depends on how much chamber you have and how hard you corner. If you get to the bands and you have a lot of tread left, chances are you are loosing traction anyways, even with new tires. Also, with the perfect chamber, when you are maxing out a corner, your tread wear will even. It’s the straight line under acceleration that will wear out the insides prematurely. But when it flattens out with the road with wear and it is still moving in a straight line. It’s almost the same as if you had less chamber because the inside tire begins to lift up again.

Leave a Reply

Your email address will not be published. Required fields are marked *

Simple math! (Spam Stopper) -