Generally speaking, to help the car turn better, we want to first reduce or eliminate Ackermann effect in the steering system. We need to position our moment center so that the dynamics of the front suspension system makes the LF tire work harder. As we move the MC more to the left, the front end becomes more efficient and turns better, to a point. We have covered where the MC should be located for dirt and asphalt racing in past articles.
Finally, we need to balance the spring setup. What we have discovered is that the front roll stiffness exceeds the rear roll stiffness in a tight setup. A front suspension system that is stiffer than the rear end will produce an unbalanced car that is tight and won't turn the corner. An excessively stiff RF spring and/or a RR spring that is too soft can help cause this imbalance.
When we're trying to make...
When we're trying to make a pass, it is critical that the car turns when we're coming off the turn. Getting good forward bite and being able to turn under the outside car helps us complete the pass.
Turn Entry and Exit Handling
The entry to and exit from the middle are affected by transitional components in the car. Transitional components include the shocks, rear roll steer, brakes, rear steer, camber change, rear stagger, and the "Anti's" (dive and squat).
We usually want to work with corner entry first. Problems associated with entry can carry on into midturn. Many times, a driver may feel very uncomfortable with entering a turn. The car just does not take a good set as he or she begins to brake and turn left. This feeling causes the driver to back off earlier and to not go as deep into the corner as other cars. This problem can be associated with how we arrange our springs.
At higher-banked tracks, say 12 degrees or more, a setup utilizing a stiffer right-front spring and/or shock compression will tend to load the crossweight percentage on entry as the car is braking and starting to turn left. That is because the LF will dive more than the RF on braking, momentarily generating added load to the RF and LR tires. This elevated crossweight percentage, or added bite, feels good to the driver, who knows that the rear end will stay under the car.
At flatter racetracks, especially on dirt, we have a very different cause and solution to the problem. When we apply the brakes going into the corner on a flat surface, we want the car to begin to roll in the same direction as it ultimately will in the middle of the turn. If we set up the car with a stiffer RF spring, the car will do a sort of flip-flop, first starting to roll left when braking and diving (due to the softer LF spring) and then rolling to the right as we continue to roll through midturn. This is sometimes visible to the observer watching from outside the car.
The solution is to run a LF spring that is stiffer than the RF spring. As we brake into the corner, the RF spring will compress more than the LF spring and the car will begin to roll to the right. As the car continues on to midturn, it will continue to roll more to the right and the transition will be much smoother, enabling deeper corner entry.
Spring split has such a profound...
Spring split has such a profound effect on the rear roll angle because of the direction of the resultant force in the rear suspension. Softer right-rear springs over the left-rear spring causes additional roll angle. A softer left-rear spring reduces the rear roll angle and makes the rear stiffer.
6. SHOCK DESIGN BASICS
For a car to be fast, the driver must have a good feel for what the car is doing. A soft ride that feels sloppy does nothing to give a driver confidence in knowing what the car will do next.
Many racers think that increased compression in the shocks should help this problem, but too often that has an opposite effect. The car may indeed need more compression in the shocks, but the rebound should always be higher than the compression to control excess body sway and roll. In most cases, just increasing the rebound resistance will solve the problem.
Again, with the big bar and soft spring setups, excess movement of the suspension can be a problem. Higher rebound rates are essential for controlling suspension movement. Many of the tech support persons who work for short-track shock companies have worked out shock valving solutions for those who want to experiment with the BBSS setups.