How wild swings in sim data are skewing a vital area of 2026 F1 development

On a weekend where one Formula 1 team has said it hasn’t even let its drivers ‘test’ its 2026 car in the simulator yet, the new ruleset has begun to take on the aspect of a large-scale thought experiment.

So extensive are the changes – narrower, lighter cars with active aerodynamics and a 50:50 split of power deployment between the electrical system and the internal combustion engine – that definitive sim models are some way off. But while the teams can work on these, and the car concepts themselves, for several more months before signing parts off for production, tyre supplier Pirelli faces a more imminent set of deadlines.

The first of these is this Monday (1 September), when it has to provide the teams with details of the construction of the new tyres, which will be narrower by 25mm at the front and 30mm at the rear. But Pirelli has revealed that the development process has been complicated by the immaturity of the teams’ simulator models.

While the FIA has set target loads, Pirelli says the simulator data it has received often differs from those figures – and that the difference between teams is in the order of up to 30%.

“When you see differences of 20 or 30% in loads, then you ask yourself which is the correct one,” Pirelli chief engineer Simone Berra told media including Autosport ahead of the Dutch Grand Prix at Zandvoort.

“So obviously we are considering the worst-case scenario at the moment because we have to be covered in case of some loads. Then we will try to check during the season and try to have a proper evaluation.”

Since the tyres are homologated ahead of the season, the onus is on Pirelli to get it right first time. It also has to ensure the tyre family can survive the additional loads generated through the inevitable in-season development.

An in-season change is possible (and has happened before, in 2023), but would require a unanimous vote in the F1 Commission, or for the FIA to wave it through on safety grounds. The latter would be more likely since inter-team agendas and politics militate against unanimity in any vote involving the competitors themselves.

Sauber sporting director Inaki Rueda said on Friday that the two reasons for not “exposing” its drivers to its 2026 car in the simulator yet were logistics and fidelity. If a driver is in the sim for a day to prepare for the next two grands prix, the 2026 simulation would sap time from that; also, the 2026 car is still developing at “a big rate” in his words.

“I know the date we’re going to start exposing the drivers to the C46 car,” he said. “But you don’t want to do it too early with the fear that the car that you’re going to show to them is still very different to what they will actually drive.”

The simulations are likely to remain in a state of relative immaturity until late October or early November, which complicates Pirelli’s ability to hit the final deadline of 15 December, when the compound choices must be decided.

The scope and scale of the rule changes are what has driven the uncertainty. It’s understood that different teams are arriving at wildly varying solutions to some of the challenges posed by the new regulations.

Gabriel Bortoleto, Sauber, Pirelli test Silverstone

Photo by: Pirelli

One factor which has a large bearing, on top of differing aerodynamic configurations, is the size of the brake rotors. At the moment these are broadly the same, but it is understood that some teams are experimenting with smaller discs at the rear with the intention of letting the energy-harvesting process contribute more of the braking effort.

This will have a knock-on effect, not just in terms of weight but in heat rejection, which will affect tyre temperatures.

“I think next year we will see different approaches from this point of view,” said Berra.

“Also we are exchanging information with the teams to try to understand which kind of temperatures we are going to see on the tyres. Mule car testing is not really relevant because next year we will have a completely different wheel assembly.

“But yeah, I’m pretty sure that we will see a lot of differences in what the teams will try to manage the temperatures of the two axles. Also from their side there is no convergence in terms of simulations in temperatures, but as I mentioned before also in terms of loads.

“So we need to understand who is closer to the reality and who is not.”