The low and flat attitude...
The low and flat attitude is both desired and common these days. We will explore its merits, how it is possible, and some of its drawbacks.
The curiosity is still there, possibly stronger than ever. The most asked question among asphalt racers is: How can I convert my more-conventional setup to running soft springs and a large sway bar-the Big Bar, Soft Spring setup? I have written two articles on the subject, against my better judgment and inclination, because I have to address technical issues at hand whether I like the trend or not. But I recently had a revelation about bump rubbers and its ugly cousin, coil bind.
A Test That Went Wrong, and Right I was involved with a redesign of a Daytona Prototype and we tested the car at a handling track, as opposed to a Daytona with high banks. We had developed what we thought was a balanced setup similar to one that had been tested before and worked very well. Why do I spend time with road racing cars? To learn things that might cross over to circle track racing. And learn I did.
First off, we ran our setup and it was tight-very tight. This was a surprise. Then our guest engineers on the test, none other than Steve Cole and his assistant with Pratt and Miller, the famed race car engineering firm out of Michigan, had us install the setup they had developed into the car. I was immediately concerned. From my analysis, the car was going to be very loose with the front end rolling much more than the rear. I even told the driver, Buddy Rice of IndyCar fame, to be careful for that reason. Surprise.
The car went out, it went faster and it was not loose. In fact, a lot of good things were happening including better grip on exit, better high speed control, and more. How could this be? I thought about it overnight and in the morning before we were to test again, the answer came to me. The relationship between what had just happened to this DP car was exactly what happens to our stock cars when we go into coil bind or onto bump rubbers.
The whole idea of soft springs...
The whole idea of soft springs and soft sway bar came directly from Cup racing. Unfortunately, we don't have the engineering support to accurately model our cars, or do we? You can plan out your setup to work if you understand the basics of the BBSS setups and how the arrangement of springs causes the effect to work.
The DP car was rolling onto a short bump rubber they call a packer at the outside front wheel in each slow turn. This increased the spring rate on that corner to what we estimated to be several hundred pounds and the roll stiffness increased reducing the front roll angle to nearly the same as the rear, making the car neutral in dynamic balance. Halleluiah! I knew I was onto something here.
Subsequent calculations done on a spreadsheet format confirmed that the increased spring rate of the outside front wheel had sufficiently altered the roll characteristics so that the setup worked. Did Steve anticipate those results? I don't know, I haven't spoken with him as of the time of this writing, but I suspect since he had developed his setups before knowing the packer gap and bump rubber rate associated with the amount of shock travel we would see, the answer might be no.
What This All Means In
our world of stock car racing, we have trends that come about and hang around for five years or more. The current trend of running big sway bars and soft springs has been here longer than that, but is growing among racers who don't necessarily understand how it works. The truth is, none of us understands it completely. Now I have a perspective.
I have always suspected how it all works and why anyone would want to go there in the first place. Dig out those first two articles and you'll see my thoughts on it. But now things are different, I have a means to explain how it works and exact calculations to prove it.
The goal in all of this is, by admission of numerous teams who live by this sword, is to lower the front of the car to the point of running a level attitude devoid of roll and where the front valance is restricting air from flowing under the car. This attitude is supposed to create more downforce in the front end, increase the front grip to turn the car, and serve to lower the center of gravity thereby reducing load transfer and keeping more load on the left-side tires. And it does do all of that, if done correctly.