For those of you who missed Alex's amazing performance at Drift Atlanta...
I can assure you he knows his stuff - There's a lot to learn from this article.
( c/o www.battleversion.com )
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I would like to start off with telling you to FOERST look for books on race vehicle dynamics and suspensions. One of the best books with easy to understand explanations is Inside Racing Technology. Also look for any books from Carroll Smith as they are all good. These books will give you the basic knowledge you need to better understand what is happening to your car as you make changes. A few basic things you should understand are tire characteristics, traction circles, and suspension geometry and how they affect the car.
There are a few steps to take when modifying your AE86 and should be done as you improve your driving. Also take into consideration what you would be using your car for: road coarse, street, autocross, touge, as they are all different setups.
The FOERST stage of improvement will be found in shocks and springs. If you are considering any type of high performance, It would be easier to consider getting coil-overs now as part of your spring setup because you will need them later for adjustability. Short throw shocks are also a bonus, they allow you to get the maximum use of the suspension travel. Bottoming out your suspension is not good as it causes your tires to do all the work and will limit their capabilities. The next step is to chose a nice set of wheels and tires, remember your tires are the only thing between you and the road, so spending money here is the best place to do it. Pick something based on its capabilities and not by the price.
Now its time to fix what happened to your suspension when you lowered it. Anytime you change ride height there are geometry changes (basically the angles of your suspension arms). Suspension geometry changes are things you cannot see but affect the cars over all handling characteristics, such as roll center. In a short sentence, the roll center is the pivot point in which the sprung weight of your car will roll, it is set by your suspension geometry and is hard subject to get into with out the help of some physics books. We must remember the laws of physics while working on cars, for every action there is an equal and opposite reaction. Every suspension design (ie. strut, multi-link, wishbone, leaf spring) will absorb forces differently. What happens on the AE86 is that with strut type front, and 4 link type rear, the roll center changes a lot more in the front than rear, so to correct this and balance out the suspension we use an adapter to move the lower control arms down (closer to original position) which moves the front roll center closer to the original ratio between the front and rear roll centers. One other thing that is effected by the lowering in the front of your car is bump steer. Bump steer is the change in toe as the car goes threw suspension travel and the changes get worse the further from original ride height you are. You may notice a change in steering when hitting a bump while cornering, like the wheel will jolt as you hit the bump, this is one of the effects of bump steer and is also helped by using roll center adapters as they move the steering arm closer to original position.
Another change that happens when you lower your car comes in the rear end links. FOERST the lateral rod (pan-hard) will move your rear end off center. To correct this you must use an adjustable type lateral rod to relocate the rear end to center. The second is that the 4 link arms have changed angles, thus changed suspension geometry. This change is similar to roll center but works in acceleration and deceleration forces, this is where traction brackets come into play. They move the lower 2 arms closer to original position and also help in corner exit as they push the rear end down under acceleration.
The next step would be to find more traction. To get more traction you need to maximize the use of your tires. Camber settings will affect overall performance at this point and would be a good choice to play with. As you get more comfortable with the car, give more and more camber. Unlike what people believe it is not excessive camber that causes tire wear but bad toe settings (more on this later).
Next work on body and suspension stiffening. This will give the driver better control of the car and will affect overall performance. Stronger/tighter suspension components greatly affect the performance of your car and improve driver feedback. A good roll cage will also greatly strengthen the car and help driver feedback. What I mean by driver feedback is the ability to feel what is happening to the car (mainly the tires) at any given time. This helps you to feel and control the car at its limits better and to be able to keep the car at its limits easier.
Sway bars can have their benefits, mainly for high speed cornering and I would not suggest using them for anything other than road coarse. Unfortunately no one sells good adjustable sway bars so I choose not to spend the money on bad ones as they can cause more problems then help. Most of the time good spring rates between front and rear, and adjustable shocks will make up the difference. This is the main reason for purchasing front coil-overs as you will be able to change spring rates easily and cheaply. This is key to achieve overall balance on your car. What you are doing with your shocks/ springs/ sway bars, is setting up how fast or slow the weight will transfer onto and off of your tires. The sway bars will level out the car but can also take away from the amount of weight that will transfer. The amount of weight transfer is critical in the fact that the more weight you can put to a tire, the more it can push back on the car (higher traction levels).
Camber will change the way the tire will push back against the car. Since radial tires act like rubber bands, and now are made with very heavy sidewalls, the more camber you give a tire, the more lateral acceleration it will give. To a certain point of coarse. The more negative camber you run, the higher levels of traction can be achieved, but there is a down side, you must change your driving style as it makes it harder to get the weight on the tire as you have less of it on the ground for your initial turn in. On my AE86, I ran the max amount of camber I could achieve which was about -4 degree's. Now with the Negative Camber Roll Center Adjusters you are able to get a good amount of adjustability. You are able to not only get the camber numbers you want but also it gives you the advantage of being able to widen the front of the car and use all of the tire well. Widening the car also has the same basic effect of having a harder sway bar.
Now to get back to tire wear. It is not the camber settings that prematurely wear out tires (unless you never drive your car hard enough) but the toe setting. The toe setting will change with any suspension change you make and is mandatory to be adjusted after any change to the front suspension. The easiest way of adjusting this is by picking up a set of toe plates. They are just 2 pieces of metal that you put against your wheels with a tape measure slots built in. I just set my toe to 0 but you can give it safely about an 1/8inch in ether direction (ie tow out= autocross, toe in= high speed stability).
This is just a quick write up on some of the steps you should take while building your AE86 into the racer you want. I know not all people will agree with me and I wouldn't have it any other way. Racing is no fun without competition.
Alex Pfeiffer
Aka. BattleVersion
