Before: This view of Don...
Before: This view of Don O’neal’s car at Batesville shows the right side ride height during the pace laps before the race starts. The right front is approximately 8 inches off the track. This high attitude is in preparation for the high travel this car will experience once the race gets under way.
This higher, single spring rate is usually about what is recommended for single spring setups, but arrived at utilizing a much lower ride height. So, the setup hasn't changed, only the attitude of the car.
A lower attitude accomplishes several things. It improves visibility for the driver, a benefit not unnoticed by many top drivers. It's hard to see where the groove is located when the front end is above the sight line.
A lower attitude also improves aero downforce to produce more front loading. More grip up front helps the car turn which allows more rear grip to be dialed in for bite off the corners. Most of the gains come without any negative complications.
What racers need to understand is that other settings need to be adjusted to match the new ride height of these setups. If the overall position of the right front, and to some extent the left front, is lower, then the cambers will change more dramatically. Initial camber settings will need to change to compensate for increased camber gain at the RF and camber loss at the LF.
If you always ran 4-5 degrees of negative camber in the RF, you might now need to run less, up to 3 or 4 degrees less. The camber gain (more negative camber) will increase as the travel increases while maintaining the same relative roll angle.
Again, the use of higher spring rates through the turns requires the redesign of the shocks so that you can control those rates. Higher spring rates require a higher rebound rate. That is simply the way shocks are supposed to work. You provide just enough control to keep the spring movement under control and no more.
After: On the second lap...
After: On the second lap of the race, we see a very different attitude at the right front. Where once there were 8 inches of height is now zero. With the right combination of shock rates, this car will maintain a balance where the combination of spring rates at the four corners will provide speed and consistency.
As with the asphalt setups, excess use of rebound in the shocks won't improve performance and may well cause loss of performance. Tune your shock rates to the spring rates the car is experiencing in the turns.
One thing Jason impressed upon me, and something I've always agreed on, is that shocks are the last tuning tool as far as setup is concerned. He stressed that teams must get their basic setup correct and all of the other settings such as cambers, moment centers, Ackermann, and so on straightened out before starting to work with shock settings.
When he agrees to attend a test with a team, he always shows up in the afternoon, after the team has sorted out all of the various "problems" usually associated with arrival at the track and the start of a test. That way, he can concentrate on the shock changes and their affect on a car that is sorted out for the most part.
He'll never allow a team to believe that shocks are the primary setup parameter, but instead a very important tuning tool to use once the basic balance and geometry issues have been taken care of. Then, and only then, can the shock expert help the car.
Be it asphalt or dirt setups, things have definitely changed over the past few years. Making sense of the new setups helps teams choose the correct components and settings. Low attitudes help with several long-established performance enhancing concepts.
Low causes a lower center of gravity and along with that, less load transfer. Low allows better aero efficiency and downforce which translates into more grip. And in the dirt cars, low provides a better view of the racetrack.
If you decide to try any of the new softer spring setups, or you're in the process of trying to figure this out, I recommend you consult with experts such as Jason who have had a lot of experience working with these types of setup. The savings in time and money can be substantial, not to mention the value of success. How do they say it in the commercials? Priceless.