Suspension Setup - Stock Car Dynamics, Part Three

In this final segment of our explanation of racing dynamics, we will show how to apply the technology previously presented. We have learned that understanding racecar chassis dynamics helps us set up our stock cars. We have come to understand how all of the forces work in our suspension systems, and we can now adjust the components on the car to create a more balanced setup.

In Part One of this series, we learned about the early research of chassis dynamics and something about the individuals and companies that were involved. The thread of technology that had been pursued in our past only went so far. We have shown how that early technology has been refined and perfected.

Racers have, from day one, had to go about sorting out their setups using trial-and-error testing. Even in Detroit, new cars are taken to a skid pad, a circular test pad, in order to determine the handling characteristics. Numerous books have suggested that racers should use that very same method to tune the setups in their cars.

Previous technology that refer to roll axis and roll couple distribution did not present the entire picture of what was happening with the racecar chassis. What the early research did that was needed was to define certain characteristics of suspension systems and tires that would lay the ground work for further research.

In the '90s, a new thread of technology was pursued, and out of that research and extensive development came a method that addressed the goals we racers have for analyzing the chassis setup. It gave us a way to predict what the racecar's suspensions desired to do. We found that once we knew the measure of each suspension system, we could then change components to cause the suspension systems to work together for the benefit of performance. A more balanced setup, we have learned, helps a car to be fast and consistent and to maximize the use of its tires.

A balanced chassis-where both ends are working together-is what we always tried to find by using trial-and-error setup techniques. In the past, when we accidentally found a really good setup, we didn't really know how we got there or why it worked so well. Often the performance could not be duplicated when we built, bought, or otherwise acquired a new car.

Part Two of this series explained all of the elements that influence the chassis setup as far as balancing the two suspension systems. We discussed the moment center (previously called the roll center), how the moment arm works, and what the differences are between the front and rear suspension systems themselves. We also showed how the forces combine to move the chassis.

We explained how we can make the car balanced by predicting what the front and rear suspension systems desire to do and then changing components to cause them to work together. That is the most important consideration related to handling performance that we can concentrate on for our racecar. To do that, we need to have some kind of idea of what changes to make in order to accomplish the goal.

Now we will take a look at three commonly raced types of stock cars and see how we can produce a more equally balanced setup for each one. The primary influences on the base setup of the car are the front moment center location, the rear moment center height, and the four spring rates. As we discuss the setups in these cars, follow the reasoning and methods so that when you think about making changes to your car, you can move in a direction that makes sense and causes a more positive result.