New Pirelli tyres: can they really change the direction of this World Championship?

(Cover picture: George Hitchens / SOPA Images)

I admit it, the title of this article easily lends itself to being a provocation: with the current technical advantage of the Verstappen - Red Bull duo, a scenario in which a technical change could overturn the direction of the 2023 World Championship is unthinkable. But behind the championship leaders, given the minimal gaps between the other teams, every detail can make the difference...

The new stiffer Pirelli constructions are changing the performance levels

What kind of changes are we talking about? At the beginning of May, after evaluating the car performances of this year, Pirelli decided (along with the FIA) to bring forward the introduction of the 2024 tyres to this year, to be precise starting from the British Grand Prix, at Silverstone.

Steven Tee / Motorsport Images

The reason behind this choice lies in the fact that the technical evolution the cars are undergoing far exceeds the expectations of the tyre supplier, with the latter having had to play it safe and make available for the 10 teams a product with a stiffer construction, given that the compounds remain the same.

"In these first races we were able to appreciate how the 2023 cars are significantly faster than those of 2022, thanks to the development capacity that exists in Formula 1. Pirelli has worked intensely in the field of simulation in recent years, so to be able not only to supply a product that complies with the performance targets, but also to be able to anticipate any problems and react promptly. The new specification will contain materials that we had already approved for 2024, and will make the tyres more resistant without modifying other technical parameters or their behavior on the track"

Mario Isola (Pirelli Motorsport Director)

From a regulatory point of view, this change was made possible by Article 10.8.3 of the Technical Regulations, by virtue of which safety-related reasons pave the way for changes in the middle of the Championship. In fact, having tyres with a construction that is not rigid enough can even expose the car to the risk of a tyre explosion, in the worst case scenario.

Evidently the fear of Pirelli, which as sole supplier would pay dearly in terms of brand reputation for catastrophic events such as the above-mentioned, must have been more linked to the final part of this World Championship than to the central phase we are experiencing now: the performance escalation of which the technical departments are capable is so sudden as to suggest a certain advance in taking these decisions, and in my opinion Pirelli has reacted correctly in this direction.

Mark Sutton / Motorsport Images

After a short test during the free practices of the Spanish Grand Prix, with the teams who had been able to try out these new constructions on the demanding Barcelona track, the actual debut of the new product took place at Silverstone. And with it, the controversy began.

The performance level, Verstappen aside, has deeply changed in the last 3 or 4 Grands Prix before the summer break. One then wonders if these performance oscillations are due to the development packages introduced at each event, or to the new Pirelli tyres...

"In all of the free practices we saw a somewhat strange grid... Partly due to the track, partly due to this new tyre construction by Pirelli, which we don't talk about much, but which changed things. At Aston Martin we had a drop in performance out of nowhere, whereas Alfa Romeo and McLaren are suddenly going faster. When you change the rules in the middle of the championship it's never nice"

Fernando Alonso

Immediately after the qualifying of the Hungarian GP in Budapest, Fernando Alonso explained in this way the disappointing grid positions in which the Aston Martin duo finished. Pretty curious, however, that Mike Krack himself - Team Principal of the English team - gave a totally opposite opinion, attributing the waning performance of the AMR23s to a flaw in the development plan.

Similarly, the leap forward made by McLaren has its roots in a particularly effective update package, which completely turned the behaviour of the MCL60 (at least on the tracks that don't require a low level of downforce). What to say instead of Alfa Romeo, mentioned by Alonso among the teams that would have benefited from the new Pirelli construction? It's true that there have been some aerodynamic developments, but what we saw in Hungary cannot - in my opinion - be explained solely by technical progress and a particular affinity to the Hungaroring track.

So let's try to understand why a change in tyre construction can have such important effects on the behaviour of a car on track, digging a little deeper into the technical aspect.

What effects does a stiffer tyre sidewall have?

Whereas on a straight line the mechanical grip provided by the tyres is a disadvantage rather than a strength (in fact we often talk about "rolling resistance" associated to a tyre), when cornering it's instead necessary to have a strong adhesive effect between the tyres and the asphalt, to approach the corner at the highest possible speed.

Force diagram on a tyre during the cornering phase

The forces that act during the cornering phase are well highlighted in the image above, where a right-hand corner is taken as an example:

• The inertial force tends to move the vehicle away from the trajectory: in the case under examination, observing the car from the front, this force is directed towards our right side, and is proportional to the speed squared (being its expression equal to mv²/r);
• The grip ensured by the tyre is proportional to the sum of the car's weight (mg) and aerodynamic downforce (F_aero), according to a friction coefficient between rubber and asphalt called μ; this force thus described is directed towards our left, so - as anticipated - opposed to the inertial force;

At this point you will have understood how the two forces above-mentioned oppose each other: as long as the grip ensured by the tyre is greater than the inertial force, the vehicle manages to stay on its trajectory; otherwise, the grip loss becomes harmful and - very often - irreparable.

The characteristics of the tyres are included in the equation in various ways: as the laps go by during a stint, the coefficient μ decreases due to wear and thermal degradation, so - being the car weight and aerodynamic downforce equal - we'll have less grip available; in addition to this, the stiffness of the tyre construction - and here we can give an answer to the previous dilemma - determines a sidewall deformation well outside its design conditions.

Andy Hone / Motorsport Images

The deformations of the tyre construction strongly dictates the ride height of the car, especially in a technical context in which the suspensions are really very stiff... In turn, the ground clearance determines the aerodynamic downforce (F_aero) obtainable from the underfloor of the vehicle, so it becomes clear how this discussion goes well with what we exposed in the force diagram: less grip requires a lower speed when cornering, in order to avoid any grip losses!

In short, as often happens in Formula 1, the aerodynamic effects act as a "bridge" between phenomena which in themselves wouldn't have much in common: eventually, the competitiveness of a single-seater actually depends on these forces!