This late-model on a skidpad is cornering flat, and the tires are working at maximum tract
Every member of a race team crew should have a basic understanding of race car dynamics. For a crew chief and a driver, a thorough understanding of the topic is paramount to success on the racetrack. As we approach the new millenium, the base of technical information increases, and that affects auto racing as much, if not more, than any other activity. Those possessing the knowledge will be in the game; those applying the knowledge the best will be the winners.
Race car dynamics is, simply stated, the study of the forces that affect the performance of a race car. The reality is that the race car system, the forces acting on it, and the way those forces are controlled is a very complex system--one that few engineers fully understand. But there are some basics that must be understood for a driver or crew chief to find a really competitive setup. You may get lucky with a successful setup even without a basic understanding of dynamics. But the more you know about race car dynamics, the better you can apply your knowledge to consistently obtain the best setup for any given track.
For our purposes, this means that getting the race car around the racetrack as quickly as possible is our major goal, and the one we will look at here. To bring this down to the simplest factor, all we really care about is maximum acceleration, braking, and cornering force. That means finding the most traction possible within the parameters in which we work. Whether it's for a single lap in qualifying, or for 100 laps in a long race, we want to find the most possible traction for the required length of time. Here are several considerations:
It's fairly easy--or at least easier--to find maximum traction for acceleration without worrying about cornering or braking, but we must find the best compromise between the often-conflicting dynamic needs of cornering, braking, and accelerating. Also, the setup for maximum traction for a single lap is much easier to find than the setup that allows the highest possible average traction for 50 or 100 laps. Finally, many engineers and crew chiefs look at the race car system as a series of individual systems that are not connected to each other. But the systems are related to each other and no single system can be ignored if true success is to be found on the racetrack. For example, most teams view the cooling system as a way to keep the engine running at its optimum temperature. While that is certainly the purpose of the cooling system, it affects other areas of performance as well. Teams often ignore internal aerodynamics. But how air flows through the car affects cooling, along with aerodynamic drag and downforce, both major performance factors.
The final system almost always overlooked by the engineers and team members is the driver. What a driver does with the controls, when they are used, how quickly they are used, and for how long affects the dynamics of the overall race car system, and should always be considered in the overall picture. The driver has a dramatic effect on performance; often, subtle changes in technique can improve dynamic on-track race car performance.
We will look at some of the major factors affecting vehicle traction, and how fast the race car can lap the racetrack.
There are many factors affecting tire traction, most of which we have no control over. They include aspect ratio, sidewall stiffness and construction, rubber compound, ply patterns, and other more esoteric engineering features. We do, however, have control over some factors. One is sidewall spring rates (affected by tire pressures within a very narrow range). Another is static vertical load (weight percentages) within a narrow range usually specified by rules. Then there is weight transfer, again within a narrow range based on the physical nature of the car design.