For a shock installation such...
For a shock installation such as this coilover design, the shock/spring combination will move at a slower speed than the wheel. If the speed of the movement of the wheel were 5 inches per second, then due to the motion ratio and the shock installation angle that the shock/spring is mounted, the shock speed would be only 3.82 inches per second.
A more realistic layout for a very high banked track might be a pair of 6.5/5.5 shocks on the front and a pair of 5.5/4.5 shocks on the rear. We have increased the resistance for both the rebound and compression as well as introduced split valving to a degree.
Low Banked Race Tracks
For low banked racetracks, we would necessarily spring the car much softer to slow down all of the movements in order to help maintain traction. One of the basic ingredients needed to maintain grip at low banked tracks that have less grip is to soften the whole setup including spring rates as well as shock rates. As we soften the springs, we would also soften the front shocks to 5/4 valving and the rear shocks to a pair of 4/3 shocks. This is the general way shocks can be matched to the stiffness of the spring setup.
Here is where we might go back to the true 50/50 shocks. Instead, many teams want to promote left front travel with Pro-dive, soft compression numbers and a high rebound rate at the left front corner. They are trying to tie down that corner to reduce the height of the left front valance. This reduces the amount of air that travels under the car and helps promote downforce. Most of the gain from this arrangement is not more traction, but making the car turn better, which can be achieved using better front geometry at less expense.
In the Part One story, we talked about how the shock regulates the speed at which each corner of the car moves as load is transferred on to and off of the four corners. If we split the rates between the four corners, we can effectively change the load distribution on the four tires while the suspension is in motion. So, to utilize the resistance of the shocks to redistribute load, we must have load transfer taking place and that in turn causes the needed suspension movement. If the suspension moves, so do the shocks.
On many big spring stock clip...
On many big spring stock clip stock cars, the speed of the wheel, the shock and the spring are all different. If the wheel were moving at a speed of 5 inches per second, the shock would be moving at 3.82 inches per second and the spring would move at 2.65 inches per second. If the shock were mounted farther from the ball joint, then it would need to be designed with a higher rate of resistance for both rebound and compression.
Compression rate differences between a pair of shocks helps to redistribute load between the four corners of the car where load is being transferred onto a particular end of the car. At the front of the car, compression rate differences can change the load distribution on entry to the corner while load is being transferred to the front due to deceleration. At the rear, compression rate differences can help to redistribute load that has transferred onto that end from load transfer caused by acceleration off the corners.
Rebound rate differences help to redistribute load between the four corners of the car when the suspension is in motion as load is being transferred off of a particular end of the car. In the front of the car, rebound rate differences can change the load distribution on exit while the suspension is in motion when load is transferred off of the front to the rear. At the rear, rebound rate differences between the LR and RR shocks can help redistribute load on the four corners of the car, again while the suspension is moving and adjusting to the load being transferred off of the rear onto the front due to deceleration of the racecar.
We need to think out the motions of the car related to how it is driven and how the track is configured, as well as the desires we have for improvement. Tuning for corner entry can affect corner exit. Do not tune with shocks for problems that can be fixed with basic setup parameters.
A car that is tight on entry should not be fixed with installation of a high rebound LR shock that will reduce the loading on the LR tire on entry. A car that is tight on entry most likely has geometry problems. The rear is out of square, the front-end geometry is not designed correctly, or the setup is just plain tight.
Remember, the more you have to trick up your shocks and shock selection corner to corner, the harder it is going to be to be consistent. We are getting many reports of teams going to more basic designs of setup and shock selection and winning races due to consistency.
One exception is when we go beyond the normal softening of the springs into what has become known as the big bar and soft spring (BBSS) setups that have become popular in short-track asphalt racing. These setups often use super soft springs in the front and, to help control dive on entry, the teams must increase compression resistance or Anti-dive characteristics to overcome the tendency for the car to bottom out as we brake and turn left on entry into the corners.
AFCO Racing Products
QA1 Racing Shocks