DickRasmussen wrote:
MikeWhitney wrote:
michaelsmiller wrote:
Herb Adams of GM fame has a theory that softer springs with heavy sways provides more grip than relying on very stiff springs.
Can you point me to some more info on this?
Mike,
Herb wrote a book back in the 70's/80's which I probably still have. As you probably know the soft springs/stiff bars approach was the "wisdom" in those days. Even Carroll Smith advocated this. Frequently with fairly stiff shocks. At least for cars on racing slicks (I don't know about DOT R tires), the "wisdom" these days is for stiff springs, compliant shocks (for bump), and whatever bar is needed to control roll/camber/transition. Even for a non aero formula ford 1600 the track racers are at least in the "wheel rate equals corner weight" range. This does require a stiff chassis.
My understanding is that the touring car guys on Toyo's, etc. run VERY stiff springs but I have not done credible research.
Dick
Updating (correcting) what I wrote above. And probably getting way off topic
The Herb Adams book I have is "Chassis Engineering" copyright 1993. Published by HP Books. Herb absolutely advocates soft springs for max grip and says that stiff bars are needed to limit roll and camber change.
It appears, however, that Herb's advice is out of date.
Note that one major change since the "old days" is that modern shocks are available which can be very compliant at high shaft speeds . . . i.e. the shaft speeds involved in dealing with bumps while still having good control of chassis movement (low shaft speeds). When the shock allows the wheel to move "easily" with bumps/pavement irregularities the spring rate becomes much less of an issue. The high end racers also work very hard to minimize friction in the system. I don't know how much, if any, tire construction changes have contributed to the success of high wheel rates. However, they do work with bias ply racing tires. As I said earlier, non aero formula cars in road racing are in the wheel rate equals corner weight range as a minimum these days. Aero classes run at 2 or 3 times corner weight since maintaining the underbody distance to the ground is critical. FYI I changed to wheel rate equals corner weight back around 2000 when I was still very active in my CM car with very good results. In my case that means wheel rates of about 220 front and 330 rear. No rear bar. Front bar the same as I ran with much softer spring.
FYI from monitoring Andy Hollis's ST Miata thread and some other ST discussions it appears that even the "almost R tires" are fine with relatively stiff springs.
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