Preparing For The New Season- Dirt

Preparing the setup in a dirt car for the upcoming season involves some processes and knowledge of technology that has been developed over the past 10 years. The approach we advocate has resulted in a lot of success and made racing much more enjoyable for a lot of dirt teams. For obvious reasons, knowledge is not passed around freely in racing circles. No one is prone to let other competitors in on performance secrets.

The processes for dirt and asphalt are similar in some ways and very different in others. That is why we decided to split the story into separate articles so that we could speak to each group separately. As I said in the asphalt piece, if you read it first, the separation between these two genres is becoming both wider and narrower, depending on which aspect of chassis dynamics and tuning we are discussing.

You may need to go back to the asphalt article when some of that information pertains to dirt racing, too. So, all you dirt guys, just because you skipped the asphalt article and moved on doesn't mean you shouldn't go back and take in some of the technology presented in the asphalt piece.

For any race car with a double A-arm front suspension, we always start with the front-end geometry, be it dirt or asphalt. If the moment center design on your car is not set properly, then the whole car will suffer, no matter what setup you have in the car.

One of the primary complaints coming from dirt drivers is that the car does not turn well. The number-one reason for that is the front geometry is incorrectly designed. Just improving that aspect of the car's overall design can make a huge difference in performance.

The dirt car moment center design is different from that of an asphalt car. On dirt, the average g-force is much less than on asphalt because the track does not provide as much grip. So the MC needs to be located farther to the left in order for the car to work well. Trust me when I tell you that most top touring dirt Late Model teams have learned the importance of correct MC location. If not, then they are getting beat by those who do.

The dirt Late Model rear geometry layout is varied and highly adjustable. The car must be evaluated for where it is to be raced and then set correctly. The trailing arm angles affect the rear steer, and the pullbar or lift arm can redistribute load upon acceleration.

Many teams will tell you that there is a need for rear end steer to the right at times. A slight amount of rear steer to the left would probably improve lap times during tight and tacky conditions. But the use of rear steer to the left should only occur on acceleration and not at midturn.

Pushrods and pullbars that move substantially and lift arms that are allowed to move are components that will help create more bite off the corners in dry and slick conditions.

Dirt car steering systems must be designed to work in both left- and right-turn attitudes. Effects such as Ackermann could be more beneficial on dirt than on asphalt, but again, only to a certain degree. The Ackermann must be developed in the design of the tie rods' angles from a top view and not by creating differences in steering arm length.

If you were to run different-length steering arms to create Ackermann, then turning one way would produce Ackermann and turning the other way would produce reverse Ackermann.

Alignment issues, such as rear end and driveshaft alignment, present just as serious a drawback for a dirt car as for an asphalt car. There is no reason to misalign the rear end. In tests we have participated in, we have run the same lap times with the car "sideways," due to excess rear steer, and when running it straight ahead with no rear steer.

I believe that, just as stated for an asphalt car, the rear end's alignment does not need to be different from 90 degrees to the centerline of the chassis and/or to the right-side tire contact patches, and those patches need to be in line, even on dirt.