The pickup points in the front...
The pickup points in the front of the car move in relation to chassis motion. That motion involves a combination of dive and roll. Our camber change is accurately viewed through an understanding of the amounts of dive and roll our car experiences.
Once the front end geometry is taken care of, the next step is to align the tires. Included in the overall scheme of alignment are: toe of the front and rear wheels, rearend alignment and location (laterally), Ackermann steering alignment, and rear steer characteristics.
Any one of these four alignment issues can and will, if not properly adjusted, have a detrimental effect on your handling that cannot be fixed with any amount of spring change, weight distribution change, or Panhard bar movement.
Toe checking is quick and easy. Start there and remember to check the rear end for unwanted toe, too. Then, move on to stringing the car to see if the rear end is square to the centerline and that the right-side tire contact patches are inline. Trailing or leading the right-rear wheel is a crutch for a setup that is not balanced.
It appears that this car has...
It appears that this car has camber change problems with the right-front (RF) tire. The left-front (LF) tire is maintaining positive camber, as it should. The RF tire has lost so much negative camber that it is actually leaning away from the center at the top.
Ackermann used to be a tool to help an unbalanced car turn when the left-front tire was not being loaded to its full potential. As we have evolved over the past 10 years into learning how to balance the setup where the left-front (LF) tire is now carrying more load and working harder, we can now eliminate the Ackermann effect. If we do not, the car will push as the front tires fight each other and try to go separate directions.
Rear steer is another alignment issue because it can alter the alignment of the rear end as the chassis dives and rolls. There are times when we want and need some amount of rear steer in our cars. We need small amounts when racing on asphalt and larger amounts under some conditions when racing on dirt.
We need to be very careful with the rear steer adjustments and make sure we know what is happening with our rear steer and the amounts involved. The current trend on both asphalt and dirt is to minimize the amount of rear steer. Top dirt Late Model cars are getting away from allowing the left-rear (LR) tire to fold up under the suspension links to create an excessive amount of rear steer. By working with the MC design and developing a more balanced setup, they can stop using this crutch to help the car turn.
One of the easiest and most...
One of the easiest and most accurate methods to check for the presence of Ackermann steering effect is by using a laser system or strings to measure, out at 10 feet in front of the tires, the amount of steering angle each tire produces.
Once we have checked out and optimized the mechanical efficiency of the car, evaluated and re-designed the front end geometry, and aligned the car properly, the next step is to decide on the spring rates for the car. Here are some guidelines.
We need to decide on the overall stiffness we will need in our spring package first. Are we running a conventional setup or soft springs with a large sway bar? What are the track conditions as far as traction availability and banking angle? Are the transitions extreme?
The very first consideration is spring stiffness. Then we can go on to determining spring split at both ends related to track banking angle and the need for bite off the corners. A flatter track with less grip will require softer springs so the car is more compliant in order to maintain traction during the transitions of entry and exit. There will be less g-force, and a stiffly sprung car may slide rather than maintain grip.
A high-banked track is more forgiving for the transitions, and we may need a stiffer spring package because the g-force is higher, and that produces more downforce and chassis travel. We must keep the frame from bottoming out on the racing surface. Once we decide on the overall spring stiffness, we determine the front spring split.
Square your rear end and line...
Square your rear end and line up those right-side tire contact patches. Basic alignment is very important to how well your car will race. Proper alignment results in less drag and a better-reacting chassis.
On flatter tracks, and this goes for both asphalt and dirt setups, we might want to run a stiffer left-front spring. This helps with the transition into the corner on entry braking. If we brake straight ahead with a softer right-front spring, the car will roll to the right as the RF spring compresses more than the LF spring, motion ratios being the same. This matches the eventual roll direction of the car as it approaches mid-turn and feels good to the driver.
For medium to high-banked tracks, it is best to run even spring rates across the front and, as the banking increases, begin to stiffen the RF spring over the LF spring. This decreases the desired roll angle of the front end and increases stability. A Cup car racing at Daytona can achieve roll angles of under 1 degree through the use of spring split without using a large-diameter sway bar.
The rear spring split is dependent on three factors: 1) track banking angle, 2) amount of traction needed for acceleration, and 3) overall spring stiffness (i.e., conventional asphalt setup, or the Big Bar and Soft Spring setups).
Ultra-high banked tracks such...
Ultra-high banked tracks such as the 26-degree Bristol (TN) Motor Speedway require spring rates that are about double the conventional rates. The BB/SS stuff just does not work here.
A typical Late Model setup...
A typical Late Model setup for low-banked tracks might look something like this. This might even work well with a dirt Late Model touring car.
The high-banked setups require...
The high-banked setups require heavier spring rates as well as stiffer right-side rates than those on the left side. The spring rate split helps reduce the roll angle of the car, and that helps aero downforce at those tracks.