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 address:Bob.Bolles@sorc.com, 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.
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.
Howe Road Course Setup
I recently purchased an '03 Howe Chassis ASA Stock Car that had been converted for road course racing. I'm new to this type of vehicle and to stock cars in general, but I'm a subscriber to CT magazine. I'm looking for articles, books, and more that can help with chassis setup and track-side adjustments for these
type of vehicles used for road course racing. I do have some mechanical skills. I'm looking for information that is more specific versus trying to interpret circle track setups and how they correspond to road course setups. Any help is appreciated.
There are many good books related to road course cars and setups that have been written over the years. Much of the information we provide has relevance to road course racing too. There are a couple of important things that differentiate the two. For one, the front end geometry and components need to be at, or nearly, symmetrical. Some teams play with favoring right- or lefhand turns if the track you are running has a predominance of one over the other. That can mean that the higher speed turns are all one way and your setup needs to favor those, whereas the slower turns could be sacrificed and less loss of speed would be experienced.
The other important principle is crossweight distribution. On circle tracks, we can deviate from a 50 percent/50 percent distribution of LF to RR and RF to LR weight. Not so for road racing, the car must have 50 percent crossweight in order to negotiate turning both ways. You can favor one way just as I have said, but not by much. And the problem arises where the front to rear percent of weight distribution creates a need for a certain crossweight distribution that may not be 50 percent. The other important factor that comes to mind is spring rates and spring split. For road racing, the spring rates need to be symmetrical, or even across the front and even across the rear. On circle tracks, we ofen use spring split to influence the roll angle at one or both ends of the car. You don't have that luxury. You must run even spring rates at each end. So, I highly recommend installing a rear sway bar in your car to help reduce the rear roll angle tendency in order to dynamically balance the car. That way you won't need to run excessively high rear spring rates to control the rear roll.
Muscle Car Body Disadvantage?
I noticed the "house"car (CT Mustang-bodied Late Model) had a muscle car body. In pASS they are giving that body a 50-pound weight break. Do you think that evens it up vs. loss in downforce, or will you be changing your body before you compete?
We have already competed with that car and have recorded very quick lap times verses the current version ABC bodied cars. No one knows just what the downforce numbers are for that body verses the ABC. But the belief that a little aero downforce advantage only will make a car a winner is a fantasy.
I went with Dick Anderson to New Smyrna several years ago and we timed laps as quick as the eventual winner in testing prior to the running of one of the biggest races of the year there. We ran old conventional spring rates, 1,200 lb/in across the front on a big spring car. In the turns we were sitting high of the track (hence very little, if any, aero downforce) in the turns, but our times were extremely quick.
Aero downforce, for tracks that are a half-mile or less in length, is much less a part of performance than other factors. What is important about the newer bump setups is the lower center of gravity and the minimal camber change once the car is on the bumps. The tires like that and always have. Those efects plus having the proper balance in the setup so that the load distribution is correct equals not only a fast car, but one that stays fast throughout the race. We are about to test our Mustang yet again with a very experienced and successful driver. I will report on our results.