There are few things in racing that are more frustrating than getting sent to the rear along with the actual perpetrator of an on-track altercation. Most of the time, at least one of the cars that is sent back did absolutely nothing wrong. It was the aggressive driving by the other driver that caused the entire episode.

As an observer, I get very upset every time that happens. Well, dang if someone hasn’t come up with a better plan. It used to be that if you are “involved” in a caution, you go to the rear. This is very convenient for the track officials, or whoever makes the race decisions, as it isolates them from actually having to make a call or suffer the resulting criticism. It is also a lame way to run a race and has always been, in my opinion.

The solution is a rule that I just heard about and may or may not be new. It’s new to me and probably new to many of you and every racetrack should look into this. It is called the Gentleman’s Tap Out Rule, or something similar to that, and involves letting the racers regulate themselves when it comes to guilt or blame for an on-track incident.

It goes like this. You might “accidentally” overdrive your entry and get into the rear quarter-panel of the guy you are trying to pass and cause a caution to come out. Under this system, you have the opportunity to symbolically raise your hand and volunteer to go to the rear while the guy who was driven into gets to keep his/her position.

This is not only great for the sport, in the area of taking responsibility for your actions, it again removes the officials from having to make a determination about who was at fault. If the guilty driver does not take responsibility, then the officials can make the call and again, leave the innocent party where they were before being run over, if they are mechanically able to continue.

This has been tried and found successful at two Wisconsin racetracks that I know of, and may be used elsewhere. At Slinger and the Dells, the drivers were very comfortable and called fouls on themselves several times. It works, in my opinion, because if you don’t own up, everyone else knows who is at fault and you are shamed as a race car driver by the fans and your fellow competitors.

If it were up to the officials, as it was with the old system, you could just blame them for getting it wrong. Not now my friend. It’s all on you. And this makes for a much better show, a more honest sport and can actually help a driver gain fan and fellow teams support and acceptance. It takes a good human being to own up to your mistakes.

And taking this a bit further, imagine in our society, everyone taking responsibility for their actions. We have moved in a direction that is opposite of that in our government, in our police forces and in our daily lives. It’s time to start getting back to the basics of integrity and honesty and where better to start than with racing. It’ll be a good lesson for the kids, and who knows, maybe even the parents.

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

Roll Centers Confusion

I have read many of your Circle Track articles and your Stock Car Setup Secrets book. In the articles I have read that were written by you, it focuses on the Geometric roll center found by connecting the A-arm instant centers to the contact patches and determining the intersection point.

I was recently reading a race car engineering book where it described the Datum roll center which is the actual point the car rolls around. The Datum roll center was described as a combination of the Geometric and Springing roll centers. In your articles, the moment arm length is determined by the coordinates of the Geometric roll center.

Doesn’t the Springing roll center play a role in this length? For instance, if the RF spring was replaced by an infinite rate, the car would tend to roll around the RF wheel center which would change the Datum roll center coordinates thus changing the moment center length.

Could you please explain if the Springing roll center is a crucial element in determining roll stiffness or is the Geometric roll center the important one? If the Springing center is important, could you explain how to find the Datum roll center location which combines the Geometric and Springing roll centers?

Thanks for reading.

-- Kevin Kulka, Mechanical Engineering Student, Limited Late Model Driver


Your question is a very good one and it’s important to understand the difference between the two. There are two roll centers, the geometric and the rolling (Datum) center. The geometric roll center that I termed the moment center is the actual bottom of the moment arm and is used to help determine what has been called roll stiffness and the rolling moment.

On top of that, there are two moment centers, the static location and the dynamic location. The first is where the MC is located when the car is at rest and at normal ride height. The other is important and is where the MC moves to after the car dives and rolls through the turns and is a result of the changes in the control arm angles. This is where the MC location most influences our cars dynamics.

The rolling center, or the actual point about which a chassis rolls, is not a direct influence on roll stiffness and basically un-important in the dynamic analysis of the dynamic setup balance. But it does play into the whole picture.

That being said, we determine our dynamic MC location by how the control arm angles change. The change is caused by the motion of the chassis as it negotiates the turns. It is the combined dive and roll that changes the arm angles.

When we change the spring rates, or sway bar stiffness, we create changes in the dive and roll amounts, and therefore create changes in both the rolling roll center location and the MC location. So, we can say that if the rolling center changes, so too does the MC location, although they are not dynamically connected.

This is why I stress that the racer needs to know the amounts of dive and roll for their setup and track they are running on in order to determine where the MC is located. It can obviously change from track to track and with different setups.

A Tip For Sprint Cars And Midgets

Brandon Mattox, out of Cory, Indiana, near Terre Haute, is the owner and driver of car No. 28, which is a non-wing, 410 Sprint Car. At the August 3, Midwest Sprint Care Series race, at Putnamville, Indiana, he flipped in the feature. The flip bent the front axle and the radius rods that hold it in place. The damaged parts were replaced.

On the next night of racing everything went OK. On the second night of racing, while running a heat race, the threads in the ball joint, on the end of the right rear torsion bar arm, stripped out and he had to pull off the track.

What caused the threads to strip out? Forces from the flip caused the threads to be over-stressed, weakened and the normal forces of racing finished stripping out the threads.