I don't believe that basic damper design has any significant impact on the roll behaviour of a chassis.davep wrote:gridgway wrote:I'm not sure that mis-matching the shocks is a good idea. On one car I have all Koni's and on the other, all Bilstein. The gas-pressure shocks will modify the behaviour a little I would think.
The gas pressure in a Bilstein has no effect on damper rates and the 'rod force' created should always be subtracted during damper testing and eliminated from damping calculations.
The spring force created by the gas pressure can simply be added to the wheel rate created by the torsion bar.
When a Bilstein is tested it is similar to testing a Koni with a very light spring installed.
It is fair to say that the Koni is a Twin-Tube design and that the Bilstein is a Mono-Tube and that each design has strengths and weaknesses but they are both just dampers.
The sad fact is that we have no information regarding the rebound/compression damping rates of either the Konis or the Bilsteins being used so it is impossible to draw any conclusions with regard to their suitability.
What we can say is that changing the rebound/compression settings and the front to rear balance will change the transient behaviour of the chassis during braking/turn-in.
If, however, the chassis has a fundamentally low roll stiffness changing dampers will have a very limited influence in steady state performance.
Once the basic problem has been resolved then tuning dampers to match the basic weight distribution and roll stiffness can result in greatly improved 'feel' and response.
Dampers control how fast weight is transferred in both the fore/aft and roll directions. The valving for low speeds is the primary controlling factor for weight transfer. This affects the load on a tyre and can change the handling balance while weight is being transferred. Once all weight has been transferred, the damper no longer influences handling.
In general, rebound damping controls how fast weight leaves a tyre while bump controls how fast weight goes onto a tyre. Stiffer valving causes a damper to react more quickly. Softer valving slows the reaction of the damper. Stiffer valving gets the load to change more quickly. Stiffer rebound valving gets the load off a tyre more quickly and onto the opposite tyre faster. Stiffer bump valving gets the load onto that tyre more quickly.
When turning into a corner, as long as the driver is moving the steering wheel or the brake pedal, the damper has an influence on tyre loading. Braking causes weight to transfer forward, compressing the front suspension and dampers whilst extending the rear suspension and dampers. When cornering, the weight transfers from the inside to the outside, extending the inside suspension and dampers while compressing the outside suspension and dampers. When both braking and cornering take place, as they nearly always do going into a turn, both effects occur. In a left turn, the right front, which is compressing from roll and pitch, and the left rear, which is extending from both factors, are moving the most and will have the biggest influence. The left front and right rear are receiving opposite movements from roll and pitch, reducing their movement and therefore their influence.
In mid-corner, where braking and acceleration forces are small, and lateral forces are highest, all of the dampers have an influence, but damper travel is very small and this reduces the influence of the damper on handling balance.
At the exit of the corner we basically undo what happened going into a corner. Under acceleration, the rear dampers go into compression and the fronts into rebound. As cornering is reduced, the inside dampers go into compression and the outside dampers into rebound. While both forces occur in the exit phase of the corner, the left rear and right front move the most since those dampers have forces working in the same direction while the left front and right rear have opposing forces. This doesn't mean that the left front and right rear dampers do not influence handling their influence is just a little less significant
I still believe the answer to your basic problem needs anti-roll bars as the first step in reducing roll.
