Adjustable shocks can be run...
Adjustable shocks can be run on a dyno and graphed to show the rates at various settings. Here, we see a wide range of resistance for rebound and compression.This shock can be used for a wide variety of setups from fairly normal, conventional rates shown in red to the more current asphalt trend for high rebound and less compression shown in gray.
We can also work with the rear shock rebound rates to help effect changes in load distribution and corner entry characteristics. To neutralize a car that is tight on entry, a stiffer rebound setting in the LR shock and/or a softer rebound setting in the RR shock will cause more of the transferred load to be taken from the LR than the RR tire during the transitional period. This too causes a decrease in the RF and LR weight distribution percentage which loosens the handling momentarily while the suspensions are in motion.
Corner exit performance that utilizes the shocks is primarily tuned by splitting the compression settings in the rear shocks and/or the rebound settings in the front shocks. A stiffer compression setting in the LR shock will load the LR and RF corners as load is transferred to the rear while the rear suspension is in motion to tighten the car with more crossweight percent. A stiffer shock in rebound at the LF corner can help accomplish the same effect by causing a slower movement of that suspension and a more rapid transfer of load off of that corner which in turn increases the percentage of load supported by the RF and LR tires.
The trend in asphalt late-model...
The trend in asphalt late-model racing is toward softer settings on compression and higher rebound rates. Here might be a typical layout using common numbers representing rates. For entry, this might create a slightly tight entry which is desirable for deeper entry and control.
The term "tie down" is often used to refer to a shock that has a high resistance to rebound. If the rebound rates are higher for both left side shocks than those of the right side shocks, then as the car turns left (especially with quicker turning rates associated with smaller radius turns), the tendency for the left side suspensions to quickly rebound as load is transferred from the left side to the right side is reduced.
If we can stop the sudden motion, then we can keep the left side down on initial turn in and the chances are that the whole attitude of the car through the middle of the turns will be lower. A lower CG means less load transfer off the left side of the car and more retained left-side weight. For asphalt stock cars and dirt cars on higher banked tracks with grip, a higher left-side weight means more equally loaded tires, left to right, and more traction. The opposite is true of dirt cars on slick tracks.
The reverse term, or "easy up" shocks, are used to help raise the suspension quickly which does also raise the center of gravity of the sprung mass and a higher CG promotes more load transfer. Drag cars use this effect on the front of their cars to promote more load transfer to the rear tires for added traction. On dry slick dirt tracks, teams can utilize less rebound in the left side shocks and in the front shocks to promote load transfer to the right side for better side bite and to the rear for better traction off the corners.
If the shock rates are arranged...
If the shock rates are arranged in a certain way, the load distribution will not be adversely affected with the high rebound rates at the front, countered by reverse emphasis at the rear. Note the higher rebound on the LF, countered by the higher compression at the RR and lower rebound at the RF, countered by the lower compression at the LR.
In order to utilize the configurations we have discussed here, we must be able to use a range of different rates of shocks in order to find the right combination for our car at a particular racetrack for a particular setup. For a team that races at only one track, the process is fairly simple. You would experiment to find the fastest set of shocks and ones that suit the driver's style and stick to those. For teams that travel to different tracks, some changes will be necessary if the setup needs to change and/or the track layout is different from track to track.
Most shock experts agree with certain basics, such as:
1. The shock package should be softer overall when racing on dirt and when the track is flatter when on asphalt for the conventional setups.
2. Get your basic setup close to being balanced before trying to tune with shocks. Shocks cannot solve basic handling balance problems.
3. Higher banked tracks require a higher overall rate of shock as opposed to flat tracks. This is because of the higher speeds and the extreme amount of downforce.