The common practice of three-wheeling...
The common practice of three-wheeling the car off the turns and down the straightaway is quickly becoming a thing of the past. More top dirt racing teams are finding more consistency by keeping all four tires on, or near, the ground.
Dirt car setup is far more complicated than setting up an asphalt stock car. In many of our articles on various aspects of chassis setup, we try to include both sides of the coin-dirt and asphalt. This article is all about dirt car setup and nothing else. It is so specialized and the techniques have developed so much over the past five years or so that it is time to spill the beans on what is working and why.
Setting up a dirt car is complicated, not only by the fact that the surface is difficult to work with, but mostly by the way it is constantly changing. You must be willing to make rapid changes to meet the requirements of the racing surface. Too many teams, surprisingly on the professional side of dirt racing, also, will come to an event and make few chassis adjustments when the track conditions continue to change drastically from practice, through qualifying, during the heat races, and finally in the main event. It's no wonder that the pole car seldom wins.
The routine for setting up a dirt car should start in the shop. A team must anticipate the conditions it will encounter at the next track it plans to race. Decisions concerning spring changes, tire selection and grooving, rear suspension adjustment, weight distribution, and even the front geometry should be finalized, and notes should be handy so the team can make deliberate and quick changes as they become necessary.
The two most common types...
The two most common types of rear suspension links are the Z-link (left) and the four-bar (right). Some teams will use a Z-link on the right side of the car...
That's easy to say, I know, but it can and is done by many of the winning teams. It's easy to write one thing and allude to changes in technology as being "cutting edge" or "state-of-the-art," but what really governs the significance of any new technology is hearing it from the actual racers, especially the ones who often win. The ones we spoke with were in agreement that times have definitely changed.
"Racers these days are more technology minded," says Billy Moyer, one of the top dirt Late Model drivers over the past 20 years. "They want to know more about how their cars work. The joy of dirt racing is being able to learn how to make all of the adjustments work together to improve the car's performance." Moyer doesn't pretend to know it all and says each year is a learning experience for him. That can be said for us all.
Brian Birkhofer, runner-up in the competitive Xtreme Dirt Car Series in 2003, states, "There is a changing of the guard happening at the end of this year . What would have worked in the past is no longer good enough." Birkhofer says his team is working to make the car more balanced, learning the exact location of the moment center design. They have already experimented with different spindles and other adjustments to find the best configuration.
...and a four-link on the...
...and a four-link on the left side. This helps them control the rear steer characteristics between the different setups.
Let's take a look at the different elements to work with on a dirt car. For the most part, we'll present information about the Late Model designs, but much information can be utilized by all dirt racers, from Stocks to Modifieds.
Front End Geometry
A good setup starts up front with the geometry of the front suspension. Don't begin to think this is not important, because it is. Furthermore, some of the top car builders in many different classes of dirt car racing, including the Modifieds and Late Models, have redesigned their front ends for better moment center location and camber change characteristics. Partial proof came to me as I was putting this story together. A team sent me the geometry data from its Late Model car purchased from a recognizable car builder; the car was very well designed. Only a couple of years ago, many other brands of this car type were terrible in their designs because none of us knew any better.
Know as much as you can about your front end geometry, and don't be afraid to change things to make it better. The most influential factor concerning the front geometry is the track's banking angle. The higher the banking, the farther the moment center can be located to the right in the car. MCs located to the left are useful for the flatter, slicker tracks.