Part One
The single most sought after goal for all racers is the pursuit of increased traction for added speed in the turns and for better forward bite. The "traction control" spoken of here is about making the tires grip better while going through the turns and while under power off the turns and down the straightaway. We will provide some valuable information about how tires gain traction and then how we can design our cars so that we take advantage of that knowledge.
There's been a lot of talk over the past few years about illegal traction control being used in circle-track racing. We know that it's been used and may have helped win some races, but there may be better ways to legally go about developing more traction, especially while under power. We know that many legal teams have been able to run faster than the ones known to be using illegal means.
Traction-enhancing technology has grown in recent times. We have collectively learned what the tires want and somewhat how to give them the opportunity to maintain grip with the racing surface as much as the laws of physics will allow. Let's face it, there are limits to everything in this physical world, so our goal is to find the achievable limits. We need to learn to recognize when we get to that limit so we can stop looking, lest we go backwards.
If traction increased at the...
If traction increased at the same rate as loading, we would see a result indicated by the dashed line. It doesn't, so we see, as shown by the solid line, that as the number of pounds of loading on the tire increases, the units of traction do not increase at the same rate. At 300 pounds of load, the units of traction are 2.4. If we double the load to 600 pounds, the units of traction only increase to 4.4 instead of double which would be 4.8.
The principle of stopping when you're ahead is true in developing a good handling package and remains true when developing the best traction package. Know when enough is enough. The word "package" is an important one, because we might well be using several different approaches at the same time to enhance traction. They rarely interfere with each other and each one will add a little to the package. Collectively, they can add up to a marked improvement in available traction.
In this two-part series, we will take a look at the various areas of influence that affect available traction and how we can maximize how our car reacts to those influences. Some are almost the same for dirt or asphalt and some of what we discuss is very different and will be talked about separately. Let's begin our lesson.
Tires
Tires, as most race car engineering books will tell you, are the ultimate connection between the car and the racing surface. That basic principle is a concept that has always been at the forefront when trying to understand ways to increase handling performance in a race car. It's also at the very top of the list when we discuss traction under power. There are five basic effects that influence the amount of traction that a set of race tires will develop:
1. Vertical Loading
Increasing the amount of vertical loading on a tire increases the available traction, but in a non-linear way. This loading can be the result of static weight increase, lateral load transfer, or aero downforce. As we increase the loading on a tire, it will gain traction, but not in an amount equal to the percent of increase in load. If a tire has "X" amount of grip with 400 pounds of load on it, the grip will be less than double if we apply double the loading of 800 pounds to it. The amount of traction will be somewhat less than twice X.
2. Contact Patch
The size and cross-sectional loading of the contact patch helps determine how much grip we will have for a particular tire. An added effect related to the contact patch and traction involves grooving and siping with dirt tires and will be discussed later.
Reducing the air pressure will usually increase the size of the tire contract patch which would seem to enhance traction, but excessively low or high pressures may reduce the loading on portions of the tire so that the total grip of the tire is reduced and we end up with less available traction for that tire. There is an optimum operating air pressure for each tire that will offer maximum contact patch area and equal loading across the width of the patch.
 When we put asphalt tires...  When we put asphalt tires on a Dirt Late Model, we need to be more aware of tire pressures and cambers. Dirt is a medium that is more forgiving for many settings, including camber, pressure, toe, rear steer, and Ackermann. |  Always check your cambers...  Always check your cambers and when you find the correct setting that will produce the optimum heat across the tread and even wear, maintain those cambers. For different conditions you might need to reset the cambers. For tight and wet tracks on dirt, more camber is required than for dry slick track conditions. |  As the tire pressure is reduced...  As the tire pressure is reduced from optimum, the pressure on the middle portion of the tire is reduced resulting in less overall grip. We may see more contact patch area, but less equal loading. |
 The same occurs as we over-inflate...  The same occurs as we over-inflate the tire. The outer edges of the tire loose pressure to the racing surface which results in less traction. At optimum pressure, the entire width of the tire contact patch will exert equal pressure on the racing surface. |  If we could look down on the...  If we could look down on the tire contract patch during cornering, we would want to see an even pattern across the width of the tire as shown. |  If the tire had too much negative...  If the tire had too much negative camber set into it, at mid-turn, the contract patch might well look like this pattern and the tire would have less overall grip. |