This old dog is still learning new tricks for sure. Just this week, I found out that a "new" technique I thought of and have been recommending for bump setups has been in use for at least a couple of years by a certain unnamed team and probably others.

The practice of pushing the front end of a bump setup Late Model down onto the bumps to set the sway bar is something I discovered, as did others, because the motion ratio difference between the left and right sides of the car caused the bar to be loaded when down, even when it was set neutral at ride height.

This and other tricks that are discovered tell us that we will never know everything and that there is an evolutionary process at work with racing technology.

I was looking through an older Circle Track magazine and checking out the technical articles the other day. In one very comprehensive (for the day) piece, it talked about roll center height—only. Back in the 1980s, the thought was that roll center height was all that mattered. This was because production cars were symmetrical in design and at ride height sitting still, the RC was always on the centerline of the car.

Still, it moved, just as our modern stock cars moment centers move, after the car dives and rolls through the turns. What we have learned is that the lateral location is much more important and has a greater effect on the front "roll stiffness" than the height.

Another area of learning is with the Ackermann. A lot of talk went on about bumpsteer, scrub radius, toe, and so on, but not too much early on about Ackermann. But one thing that started getting attention in the mid to late '80s was aero. We started seeing wedge noses on Late Models and wings on Sprint Cars.

With the space program, aero knowledge increased and became more widespread. Cars were going very fast and staying on the ground better at Bonneville due to the more sleek shapes, and some of that rubbed off on stock car racing.

The problem with the advancement of some areas of technology is when people focus too much on just one aspect of the car and develop tunnel vision. That is what has happened over the past few years with attention to aero and continues to plague race teams.

In the search for the fastest lap time, an age old dilemma, teams concentrate on making the cars run very low and level to the racing surface, ignoring the balance of the setup. So, the tires don't share the loading properly and many of these setups go away quickly as the tires heat and wear unevenly.

It's not just with relatively low buck stock car racing, including Cup racing, but also with F1 world racing. Those teams all run the same tires, and their budgets are very large, even the lesser teams. But the difference in performance is in the handling balance, period.

How do I know that? It's easy. You look at where the gains are on the track. The fastest teams continually record the slowest top speeds and make all of their gains in the slowest corners. Their cars are not only aero efficient, but the balance is there so that they are fast for a very long time. And, their tires do not degrade nearly as much as the cars running further back in the pack.

What all of this means is that some teams pay attention, learn new tricks, and advance their programs by keeping an eye out for new ideas and technology. Back when I first started developing my knowledge base and consulting, there were a number of people I became acquainted with who are still at the forefront of technical advancement and working for various companies and teams.

They were the ones who were out there looking for new ideas, not mired in the belief that they knew it all. The know-it-alls soon faded in their careers and the young learners moved ahead. No matter your age, you can still be a "young" learner at heart. It just takes the mind set of keeping yourself open to all that is out there and finding what makes sense.

If you have comments or questions about this or anything racing related, send them to my email, or mail can be sent to Circle Track, Senior Tech Editor, 9036 Brittany Way, Tampa, FL 33619.

No Apology Necessary

In your recent "Track Tech Q&A" article in the July '13 issue, you seemed to apologize for consistently providing sound and relevant technical content in your past articles. I can't speak for all readers of CT, but I personally became a subscriber mainly due to your and Jim McFarland's technical articles. I have thoroughly enjoyed and have been enriched by the details you are willing to go into and as a result, have sparked a curiosity that continues with more research and practical application.

Funny thing is, I don't race circle track; I have been racing SCCA road courses at a national level for more than 10 years and I'm an advanced instructor for the Porsche Club of America.

Your articles have been a benefit to my personal racing efforts and instructing. Please keep the tech coming.

Kind regards,

—Charles Mathes


Thanks for the kind words first of all. In that piece, I was trying to explain mostly how to read any tech article. Every writer has a point they are trying to make and regardless of how simple or how complicated the subject or the explanation, there is important information to be had.

I have quite a few people say to me that they read my articles, but don't exactly comprehend all of what is presented. It's because of those comments that I wrote that QA. Those aren't all of the comments I get.

Like yours, I get very many emails and comments that give me hope for my writing and the intelligence of our readers. Many do get the points and many do improve their racing programs. Based on that, I think I'll keep doing this for a while. After all, I am learning too.

Driver Weight Change

I help out on two different 410 Sprint Car teams and my question is related to swapping the same torsion bar setup between two drivers, one being 150 pounds and the other being about 250 pounds. We were told at one point that for every 100 pounds of weight difference up in driver's weight we should increase three to four turns at each corner.

Is this correct or should we be looking in another direction? Also, if there is any information you may be able to share on Sprint Car setup or torsion bars it would be greatly appreciated.

I'm interested in learning as much as possible about racing and have read many of the articles you have written. Thank you in advance for any advice you may be able to offer.



First of all, a heavier driver will produce a higher center of gravity in the car and that afects the setup. When the g-forces go up, and/or the CG goes up, that can afect the balance of the car. Since your 410 Sprinter is a solid axle at both ends, the change is much less than with a double A-arm front and solid axle rear.

The three to four turns you speak of are probably needed in order to bring the static ride height back to what it was for the 150-pound driver. The trailing arm angles and moment centers are influenced by the ride height and so this routine of bringing the car back to a set ride height is important. Think also about the higher CG. I ran a simulation for a Sprint Car where I raised the g-forces and then the CG, one at a time, and the balance changed. For the higher g's, the change was not so much, but for the higher CG, the change was significant to where the car would not even come close to handling the same between drivers.

For the higher CG scenario, the roll angles increased as would be expected because the CG height helps to determine the roll angle of the chassis in the turns. But when I raised it by 4 inches—from 16 to 20 inches—the rear roll angle ended up a whole 2 degrees more than the front, when the two were equal at 16 inches of CG height. To correct that, you would need to increase the rear spring rate overall, increase the rate of the right rear spring rate over the lef rear spring rate, or raise the rear moment center. One or more of these in combination would bring the car back to the balance you had with the lighter driver.