As a reminder to all stock car teams, be they dirt or asphalt racers, we present a list of the top 10 most important setup parameters each year. Each new season brings changes in the goals related to setup and to how the racer will go about meeting those goals. And so we tune each preseason list with thoughts on the current trends and how the steps might be looked at differently based on those trends.
Each trend must prove itself in order to stand the test of time. It must show a consistent gain in performance and a logical ideology to the bulk of race teams. And, it must be economically applied.
I have always believed in priorities because you can make gains faster when you solve the high priorities problems first. And, some aspects of chassis setup build on other aspects. So, here are, in order of logic and importance, a list of setup parameters we need to address to make our cars fast and consistent.
1 Front End Geometry
We always start with the front end geometry on any race car, be it dirt or asphalt. The settings, including the moment center location, really do dictate how all of the other parts and pieces of setup will work. If this component on your car isn't right, then the whole car will suffer, no matter what else you do.
Front end geometry involves not only toe setting, camber and caster, but also the moment c
A newer terminology for understanding the dynamics of the front end involves jacking force related to the location of the instant centers in the geometric layout. We'll be going into much more detail about how the moment center technology relates to jacking force in future issues.
The dynamics of the moment center and the effects of camber change have been explained in past articles. We have continually pressed these issues because of the extreme importance they have. Long gone are the days of saying that the MC is not important.
The dirt car moment center design is different than that of an asphalt car. On dirt, the average g-force is much less than on asphalt because the track just doesn't provide as much grip. So, the MC needs to be located farther to the left in order for the car to work well.
2 Rear Geometry
The second most important item in the setup arsenal is the rear geometry layout in your car. The components that locate the rearend must be evaluated and set correctly. The control arm angles affect the rear steer and the third link, lift arm, and so on and can redistribute load upon acceleration. On a metric four-link car, the four control arms determine the rear moment center height too.
Rear alignment and rear steer are important issues for both dirt and asphalt racers. The a
It's not advantageous to have the rearend steer to the right at any time on asphalt. A slight amount of rear steer to the left has been shown to help provide more traction at the rear and bite off the corners where it's needed. But the most useful rear steer will only occur on acceleration and not at mid-turn.
The dirt car rear geometry layouts are varied and usually highly adjustable. Each car needs to be evaluated for where it's to be raced and then set correctly. The trailing arm angles affect the rear steer and bite and the pull bar or lift arm can redistribute load upon acceleration and deceleration.
3 Steering Geometry
The steering system in your car must be evaluated and any negative characteristics must be eliminated. Negative aspects might include excessive bumpsteer, excessive Ackermann, and incorrect steering quickness.
Front steering geometry involves toe change as the steering wheel is turned. It needs to b
Eliminate most of your bumpsteer and Ackermann and install the correct steering ratio for your track that would suit the driver. Ackermann is easily checked by using a laser system or strings. If all of these issues are evaluated and corrected, then you can move on.
Dirt car steering systems must be designed to work the same in both left and right turn attitudes. Mechanical affects such as Ackermann could be more beneficial on dirt than on asphalt, but again only to a small degree.
The Ackermann must be developed in the design of the tie rods angles from a top view and not differences in steering arm length. That way the wheels always keep the same toe or toe gain in equal amounts while turning right or left.