Why did Pirelli implement mid-season changes to its tyre?

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In response to higher than expected loads in the 2023 season, Formula One's tyre supplier Pirelli decided to introduce a sterner, tougher construction of slick tyres at the British Grand Prix. F1Technical's senior writer Balázs Szabó analyses the reasons behind the mid-season tweak.

Mid-season technical changes are usually delicate questions as they can have significant impacts on cars' outright pace and teams' relative form. However, such immediate changes have already happened several times in the past and they are likely to happen in future as well.

It is sometimes inevitable to make tweaks to the regulations on safety grounds. Teams can, however, also push for certain changes if they feel that they can achieve a competitive advantage with a certain tweak to the regulations.

Last year, FIA stepped in to reduce the porpoising and bouncing drivers have experienced over the opening races of the season. This happened after Mercedes lobbied for immediate changes while other teams were relatively happy with the way their new cars operated. The technical directive was implemented from the Belgian Grand Prix after the summer break.

This year also saw the sport implement a mid-season technical change, but this time the tweak revolved around the tyres. Pirelli introduced a new specification of slick tyres from the British Grand Prix onwards.

The reason for the change was that the experiences gained across the opening races of the 2023 F1 season had left the Milan-based tyre supplier surprised. Pirelli was concerned by the increase in aerodynamic loads of the current cars after just one full season of development.

The new specification that was introduced in Silverstone sports a sterner, tougher tyre construction while the compound types stayed the same. The new specification features materials that had been originally planned for 2024.

Teams and drivers were able to have a first taste at the Spanish Grand Prix with each driver having received two extra sets of new-specification tyres during the Friday’s practice sessions.

Speaking of the changes, Pirelli’s Motorsport Director Mario Isola said that Pirelli had no other choice than introducing immediate changes on safety ground.

“We started the season with tyres that were carrying more than the estimated load because we have to put what we call safety margin on tyres. The real problem is that at race three they already reached the level of load expected for the end of the season. And we can imagine that at the end of the season they will have a lot more downforce.

Isola said that Pirelli could have get around the issue by implementing sporting changes which would have could have realized in the form of tweaks to the way teams use the tyres.

It would have meant that Pirelli could have raised the minimum pressure with which teams need to send the drivers out on the track. The minimum pressure values have long been a debate among drivers and engineers as it have a huge impact on the available grip.

Lower tyre pressures increase the contact patch of the tyre which leads to more grip as more rubber touch the road. However, tyres that are running at a lower pressure are more flexible and bend more through corners (lateral forces) and even under braking and acceleration (longitudinal forces). The more tyres bend the bigger are the forced the sidewalls of the tyres are subjected to. The latter have caused several failures over the past couple of years.

“So we had two options. One was to change the construction, and it is what we did changing one material in the construction to have a better resistance to integrity or to increase the tyre pressusre. But we know that drivers don’t like this approach.

"And so discussing with the FIA, we decided to have this change in construction that is not making any real change in the behaviour or performance of balance of the tyre. So it should be transparent for everyone,” Isola concluded.