In one of my latest article’s I talked about the different racing lines and how to take them. If you missed it, feel free to check it out here: Motor Sports - Racing Lines Explained. In this article, I also mentioned that the grip and the actual physics behind the state of the car matter a lot in racing. This is why in this article I want to briefly talk about the most important physic you should know, no matter whether you are a racing driver or just driving in your normal day life. I will try to make it as easy as possible and for the physicists out there: I am sorry that I will make it easy for us!
Kamm’s Friction Circle Theory
Let’s begin with the general theory. Like everything in this world, a car tire can take a certain amount of Force. When it is exposed to more force than it can handle, the result is that it will give up. In the case of our tire it means that it will start to slide and the car will loose traction.
Now that we got the basics, let’s explore what forces can act on our tire. In general there are two cases. The first one is: We are going forward or backward. In this first case our tire gets exposed to longitudinal forces which is pictured on the x-axis in the graph below. The easy case of just going forward is then the blue arrow which shows how much Force our tire is currently getting exposed to. The second type of forces are the lateral forces, which are pictured on the y-axis and in a very specific case the light green arrow. This case would be if we drove a circle and are exposing the tire to some cylindrical forces.
The last example actually has both forces in play. When we are driving a circle we have lateral and longitudinal forces which would result in the yellow arrow. But why am I telling you all of this stuff? The most important part comes now! Like mentioned before: the tire can only take a certain amount of these forces and it is shown with the red circle. Once a tire gets more forces on it, it will start to slide. This is important because normal people would laugh if you would tell them that 80km/h is a dangerous speed, but what nobody is telling them is that during a corner with high lateral forces, this speed is able to be very dangerous because of these physics effects.
Furthermore, we need to take a look at the surface itself. The red circle is actually representing a dry track. This is when we have the most traction. When the track is getting wet or has even ice on it the circles are becoming quickly smaller. This means that a maneuver like the yellow one that is actually safe on a dry track might cause an accident on a wet track. This is why racing drivers are having more often accidents in the wet and trying to keep the clean racing lines during wet conditions. It is actually also very important for the real life as keeping this in mind can safe lives by avoiding dangerous maneuvers.
Use-Cases During Racing
With the physics out of the way, let’s discuss some of the most known Use cases during racing: Over and Understeering! With Understeering we are basically telling that the car does a bigger radius than the driver wants, therefore it understeers. This happens a lot in high speed corners when the car gets wider and wider. So what is happening in this scenario? The simple explanation is: the tire just can not handle the side forces anymore. While entering not the corner, we are probably already at a very high speed therefore having a good amount of longitudinal forces on the tire. What now happens is that we are adding lateral forces through the steering. This results in exiting the circle of friction and the front tires will start to slide resulting in a bigger radius than initially anticipated.
The second case is the Oversteer. In contrast to the first use-case, in this example our car will drive a much tighter radius than commanded by the driver. In most cases, this will result in a spin which was very perfectly executed by Mazepin during the last F1 season :P In some cases and with a very skilled driver, you can use the oversteer to transition into a drift, but more on that a little later. So what happens with our tires during the Oversteer? The use case is the following, we are again on the edge of our friction circle during a tight corner. This means that we have a lot of lateral forces and also some longitudinal forces. What comes next is a heavy acceleration by the driver, meaning that we push our arrow outside of the circle by adding a lot of extra longitudinal forces. This often happens if drivers are accelerating to quickly out of a corner and forgetting to reduce the steering angle. It will result in sliding rear tires and therefore spinning aka oversteering. In many use cases spinning can be avoided by counter steering in this situation and decreasing the throttle. This way you have a chance to get you car into a stable position.
Conclusion
In conclusion, I think it is very important to keep in mind what racing drivers actually have to think about and have a feeling for. I highly admire all of them for being so calm in certain situation and being able to control the car so perfectly. Not only that but feeling when your car is on the limit is extremely difficult and requires a lot of experience and feeling for the car. With that being said, I hope you could take away something from this and maybe even learn something for your next personal drive! 😊
Published by ga38jem on
Sports Talk Social
On 9th June 2022