Motorsport Physics II
Aktualisiert: 8. Okt 2020
For F1 cars (and in the racing scene in general), the power of the cars are not the limiting factor per se. With immensively powerful cars like F1 bolides with over a thousand horsepower, the problem is, how you will accomplish to bring this power to the ground.
The four tyres of an F1 car have a contact surface, in technical terms called tire contact patch, of together about 4 times ...
… of this. As you can see, it’s not a huge surface, making contact with the ground. And the magic is, to bring down the most energy down on the asphalt. There are three key factors for a successful and high power transmission to the road:
The launch or, when already driving, the amount of power supplied to the tires: If too much power is send to the tires, than the contact surface to the ground, the ground itself and tire condition (temperature, rubber properties and condition) are allowing, you will experience wheel spin (which will cost you precious seconds on the circuit and a lot of unused energy).
The condition of the tires: tyre properties (slick, wet, intermediate etc. and the wear on the tires, as well as the tempereature)
The condition of the ground (asphalt) itself: Wet or dry conditions, surface structure.
The ability and the extent, with which a car can bring the power down on the ground, is called grip.
Ideal Line – Apex Speed
The so called ideal line is the way on the racetrack, we imagine ourself, which offers us the fastest way through the corner. Means, that with driving the ideal line, you have the biggest possible radius of curvature (as seen on the picture, r1 = low radius of curvature, r2 = high radius of curvature).
And with an higher radius of curvature, you are able to drive through the turns with, in average, higher speeds. And these speeds in the curves of a racetrack are messured as the so called Apex Speeds. The apex is normally the point of the curve, which has the maximum curvature:
When rain hits the racetrack, you will be best off with the rain line, which has an even wider radius of curvature to prevent too high centrifugal forces, pushing the car off the curves and in worst case revoking complete grip to the ground -> skidding or even spinning can be the consequence.
A racetrack has multiple ideal lines. Depending on the basic conditions of the circuit, like with which speeds you are allowed to drive through the corners. But also subordinate to what car you are driving and what your purpose on the track is with the car (F1 bolide, DTM, drift challenge, flying lap, etc.).
You’ll find ideal lines not only in the motorsport genre. They are also existing in marathons, bicycle or ski races for example.
To have fresh and warm new tyres fitted is absolutely magnificent! You can push your car to the absolute limits. It’s statistically proven, that you are only able to run the fastest lap, when the tires are grippy enough. And normally that’s the case with only fresh new tires. Because afterwards, after every single lap the tires lose about 1 - 2 % of their performance. If the driver pushes the car very hardly, the aging of the tires can reach up to 3 % each lap. Reasons for that are:
The lateral forces between tire and ground
The high speeds -> warming up the tires -> warm tires wear faster
Driving mistakes -> driving through unsuitable terrain
That means an efficient tire management is crucial for a successful trackday.
The tires, when they are completely new and fresh from the factory, they have a slim film on the surface of the rubber, which provides very high grip. Peak grip I must say! And you maybe have noticed, that while the F1 cars stay in the box and are getting ready for the race, the pit crew are wrapping the fitted, fresh tires into a thermal blanket. That is, because it would be a huge waste, to not use this peak perfomance of the tires, which is provided by the mentioned film on the surface.