Photo by Keith Cyr
The track banking angle has an influence on traction and roll angle. There is a high amount of downforce associated with high banking and as such, a spring split in the rear of the car introduces additional roll angle influences. A split where the left-rear spring is less than the right-rear spring causes the rear to roll less. A softer RR spring will cause the rear to want to roll more.
The high banking and associated higher downforce puts more load on the rear tires to the extent that there is seldom a traction problem when exiting the corner. So stiffening the RR spring is acceptable for high banking angles, whereas the stiffer RR spring may hurt turn exit performance with a lower-banked track.
With low banking angles, we usually have a need for better bite off the corners. Using a softer RR spring helps because, as the car transfers load to the rear under acceleration, the stiffer LR spring causes a momentary increase in the crossweight percentage while the car is accelerating. This tightens the car so that more throttle can be used on exit.
The rear springs greatly influence the rear's tendency to roll. Stiffness is secondary to the spring split in roll influence. So, to keep the car balanced, the Panhard bar must be raised in conjunction with softening the RR spring and/or stiffening the LR spring. In a split where the LR spring is less than the RR spring, the Panhard bar must be lowered to maintain the same roll tendency.
Most shock manufacturers and many independent dealers offer shock maintenance and shock re
When we have sorted out the geometry issues, aligned the tires, and chosen the spring rates, we then, and only then, work with the shocks to fine-tune the transitional handling.
Most top shock company reps will tell you right up front that you need to sort out the basic setup before working with the shocks. That means getting the car to handle through mid-turn first. Then you should work on turn entry and turn exit with the shock package.
Make sure those shocks are working properly. A simple test is to push down on each shock to feel the smoothness of the motion. The resistance will only be valid for low-speed jetting, but we are trying to determine if the shock will cycle without sticking. Having the shocks dyno'd by a professional shock technician is a better idea. That way you will know the exact rate for each increment of speed of shock movement.
Shocks control the speed at which each corner of the car will move when the dynamics of turn entry and turn exit come into play. Shocks do not influence weight distribution at steady-state, mid-turn attitude, but they do regulate the distribution of loads during the transitional periods.
If we slow the motion on one corner of the car as load is transferring onto that corner, momentary loading will increase on that tire as well as the diagonal tire. On turn entry under deceleration, the RF and LR tires will gain load if we stiffen the compression of the RF shock. This will tighten the car on entry while load is being transferred to the front.
If compression is increased at the LR, then as the load is transferred to the rear while under acceleration, the LR and RF tires will gain excess momentary load while the load is transferring.
The rebound side of the shock can cause reduced loading of a corner of the car when load is being transferred off of that corner and the rebound resistance is increased. This reduces the loading on that tire as well as the diagonal tire. Tune accordingly.
The radius of the turns and the track banking angle determine the amount of rear tire stag
There are several settings that should not be used as tuning tools. They are as follows: rear stagger, tire pressure, camber, rear alignment, Panhard bar split (except on dirt under some slick track conditions), and excess brake bias settings.
The rear stagger should match the average track turn radii. The tire pressures should be set to even out the tire temperatures across the tire surface. The tire cambers should be set to also even up the tire temperatures with a preference to slightly higher inside (toward the inside of the racetrack) temperatures. The rear alignment should always be square with the chassis. Panhard bar split should not be used to tune the car. There are jacking tendencies with bar angle that move load around in the turns, and this makes the car inconsistent. Never try to fix a tight-in problem with excess rear braking bias. Fix what is causing the car to be tight in, such as setup balance, shock rates, or Ackermann.
Look to past articles we have presented in Circle Track for more detailed explanations for each area of chassis setup. If you can quickly evaluate that "new to you" car in the order given here and then make the right corrections where necessary, your chances for success will be greatly increased, and the level of frustration that often accompanies working with unfamiliar cars will diminish.