For a shock installation such as this coilover design, the shock/springcom-bination will move at a slower speed than the wheel. If the speed ofthe movement of the wheel were 5 inches per second, then, due to themotion ratio and the shock installation angle of the shock/spring, theshock speed would be only 3.82 inches per second.
It is important to note that, contrary to some opinions, the weight transfers almost immediately when a force is presented to enact that transfer. As we brake into the corner, the weight transfer happens quickly. If we transfer 300 pounds on entry from the rear to the front, the 300 pounds goes to the front in an instant. The distribution of that 300 pounds between the two front wheels, while the suspension is assuming a new attitude that will support the additional weight, will depend entirely on differences in stiffness of the suspension systems at all four corners. Stiffness is defined as the resistance to movement of the shocks and springs.
Reasoning out the effect of weight transfer onto the front suspensions that are dissimilar in stiffness, the slower moving (or stiffer) corner will momentarily retain more of the transferred weight while the suspension is moving to a new attitude to support the added weight. If the RF suspension is stiffer than the LF suspension, then both the RF and LR tires will support more of the total sprung weight of the race car.
Crossweight is defined in short track racing as the percent of the combined RF and LR weight versus the total vehicle weight. If the crossweight percent increases, the car will be tighter on entry and the car might be faster if that is the desired effect. This is exactly why it has been said that a stiffer RF shock will speed up weight transfer to that corner. In truth, some of the momentary weight that has been transferred onto the RF due to that corner being stiffer than the LF corner may well return to the LF tire as the car reaches a steady state or a steady ride height at mid-turn.
On many big-spring stock-clip stock cars, the speed of the wheel, theshock and the spring are all different. If the wheel were moving at aspeed of 5 inches per second, the shock would be moving at 3.82 inchesper second and the spring would move at 2.65 inches per second. If theshock were mounted farther from the ball joint, then it would need to bedesigned with a higher rate of resistance for both rebound andcompression.
If the car is already tight on entry, after having eliminated common causes of tight entry such as rear misalignment or brake bias issues, an opposite effect can be utilized. If we increase the compression of the LF shock and/or increase the spring rate on that corner (which is usually a good idea for flat tracks), we can effectively reduce the crossweight in the car on entry while the suspension is in transition by loading the opposite diagonal, the LF and RR. As one diagonal goes up in percentage of supported weight, the other goes down.
We can also work with the rear shock rebound rates to help effect changes in weight 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 weight 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 that loosens the handling momentarily while the suspensions are in motion.
Exit Tuning Using Split-Valve Shocks
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 weight is transferred to the rear while the rear suspension is in motion. 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 weight off of that corner which in turn increases the percentage of weight supported by the RF and LR tires.