I did mean in use, on a road race car, the springs (all four), the springs will acquire a frequency cycle, which the dampers react to and attempt to control. If this frequency cycle comes into the same "percentage of range" or "equal" for the front and the rear, the chassis ride will be affected negatively, increasing the potential for handling problems and negative, inappropriate reactions to bumps. This can be canceled out by simply changing the spring rate to alter the frequency.DaveW wrote:
Good question, & one I can't answer simply. However, it is worth noting that a spring doesn't have a "frequency", as I'm sure you know. The comment is worth making, however, because your statement implies, perhaps, that a quarter car model can be used to set springs & dampers. The technique certainly is used in the road vehicle world to decide on spring selections (spring_stiffness / corner_spring_mass). The concept is flawed, however, because tyres do affect vehicle natural frequencies & the two axles of a vehicle are not isolated from one another, but are connected by the sprung mass.
With tires, shock technology (and the J damper) has come to the point of controlling not only the frequencies of the chassis (mostly at the spring level), but also the frequency cycles of the tire. As we can't change the spring rates of the tires except through tire pressure (easier done with radials as they don't have tire center growth problems with pressure. Almost impossible with bias.)
It is interesting to note that your finding of the ratio of tire ratio spring rates have a "sweet spot", that in my opinion has a correlation to this frequency balance.
Wouldn't a rise in spring rate require a reduction in shock dampening? And on the other end, a lower spring rate, an increase in dampening?In other words, the mechanical suspension set-up problem is not one of optimizing two second order systems (or even two fourth order systems if tyres are included), it is one of optimizing a single eighth order system, with (actually) many non-linear parameters. An asymmetrical vehicle (e.g. NASCAR) raises the complexity yet again. A satisfactory solution to the problem (in general) can only be obtained using a full vehicle model or a hardware-in-the-loop test using multi-post rig.
To illustrate, start with a completely symmetrical vehicle (c.g. at 50%, same springs, dampers & tyres at each axle). If the front springs are required to be increased, then a quarter car model would suggest that the front dampers should also be increased. Usually, however, increasing the front springs will imply that the rear axle will dissipate more of any disturbance energy, so the correct change would be to increase the rear dampers. When the ratio of tyre/spring stiffness is small, the spring change would probably require some combination of increased rear damper settings, reduced front damper settings, reduced rear springs, & increased rear tyre stiffness. Parameters very definitely become highly "coupled".
Wouldn't increasing both the dampening amount and the spring rate, result in an "undershoot" of the spring (by over dampening the spring) in restoring it to rest?
****As the natural frequency of a stiff spring (without a damper involved), returns to rest quicker and in less cycles than a softer one.***
Are the current F1 tires and their alternate compounds,IE: Soft, supersoft etc. all of the same construction with different compounds or do they alter the construction as well?Why is tyre stiffness important? Because they have to support the suspension & transmit suspension loads to the road surface. It follows that tyres (or, more accurately, their vertical stiffnesses) are an integral part of the suspension of a vehicle. It turns out that having a stiffness split that corresponds with the sprung mass c.g. position is a good starting point. Tyres that don't have the "correct" stiffness split can be accommodated by making suspension adjustments; if other (usually driver or aero) requirements mean that this in impractical, then the alternative is to move the sprung mass c.g. position, which is what F1 teams have been doing for the last few years. There is a compromise to be made in that case, however. Moving the c.g. (& centre of pressure) forward improves vehicle "mechanical" control & tends to increase front tyre temperatures, but it will reduce traction...
Tyre lateral stiffness split is also important, principally for the driver. A vehicle that sideslips under lateral loads affects a driver's ability to operate close to the "lateral limit" of the vehicle (& its tyres).
Yes it has. Having spent a lot of time with the cars you mention, except F1, and time at 7 posters with assorted cars, I'm interested in your view, as someone who appears to have spent a lot of time around poster rigs.As I said at the start, your question is difficult to answer. I hope the above will help a little.