F1 Tech | Did the new flexi-wing directive help Ferrari over McLaren?

Who is the target of the new technical directive? 

The Chinese Grand Prix weekend started off with the new technical directive related to the flexing of the rear wings, which was issued by the FIA on Monday after the Australian Grand Prix. The flexing of rear wings is something that started to take off after last season’s Azerbaijan Grand Prix, when it appeared that McLaren was taking advantage of the carbon fibre bending on the rear wing to generate the so called ‘mini DRS’ effect that provided higher top speeds when the DRS system was not activated. After that, the FIA declared that spec of rear wing illegal and McLaren had to build another model of the same spec but with stronger materials, to avoid the aforementioned bending. 

Despite this controversy, the problem was related to the fact that that rear wing was actually legal, as it successfully passed the static tests imposed by the FIA and thus was legal in all respect. 

For this season, the Federation decided to gain further data on the cars’ behaviour at high speed by placing video cams and stickers on every team’s rear wings during free practices in Melbourne, to analyse their displacement at high speed, i.e. when the high pressure generated by the speed and aerodynamics tends to make the wing flex. This experiment allowed the technical department led by Tombazis to have a clear feedback from the track. This added to the static tests carried out at the start of the weekend, where each car’s rear wing was subjected to a load of 750 N (i.e. approximately 75 kg) and the thickness of the "slot gap”, i.e. the gap between the mainplane of the rear wing and the DRS flap, was measured. 

At the end of these tests no car was defined illegal or not compliant to the regulations and thus this test seemed to be made just to check that everything was in order and was archived after second practice.

On Monday, however, the FIA announced a new technical directive concerning the rear wing, that would have come into action starting from the Chinese Grand Prix: “More specifically, Article 3.15.17, introduced in 2025, states that if 75Kg of vertical load is applied on either extremity of the rear wing mainplane, the distance between the mainplane and the flap (also known as “slot gap”) must not vary by more than 2mm. From the forthcoming Grand Prix in Shanghai, this limit will be reduced to 0.5mm. Due to the short notice for Shanghai only a tolerance of 0.25mm will be added to this new limit.”

This change aims at stopping some teams from using regular but advantageous solutions that could give a gain in terms of performance. Asked about these changes by Sky Sport F1, FIA Single Seater Director Nikolas Tombazis, answered: “It was quite clear from the start that the measures taken for this year on the rear wing were a little bit insufficient, so in this right way, to avoid this discussion spreading over many races, we decided to be incisive and we made this change for this race.”

Due to the short time available, teams who had borderline solutions adopted 2 different strategies to solve these problems ahead of this weekend: the first one was by injecting thermosetting resin in the carbon fibre, as it should make the fiber much more resistant to load and stress; the second solution consists of multiple layers of carbon fibre that are added to the mainplane and DRS, making them heavier but avoid blending at high speeds (this solution may be better but it’s a disadvantage in terms of weight).  

However, from the Japanese Grand Prix onwards, the limit will be set concrete at a maximum of 0.5 mm, removing the additional 0.25 mm that were in place for Shanghai because of the short notice. 

In the paddock it’s said that this new technical directive should limit McLaren and give an advantage to Red Bull, even if as we already explained in previous articles, McLaren seems to get their biggest strength from having a very good performance in corners and a very good balance between aerodynamics and mechanical system rather than by just the top speed. 

Ferrari in strong form, McLaren with messy laps 

Moving now on to analyse what happened so far this weekend, during FP1, McLaren seemed to be the car to beat, showing off a very competitive pace both in the qualifying simulation as well as in the long runs, with Ferrari, Mercedes and Verstappen all very close to each other.

However, the scenario completely changed for qualifying, where Ferrari made a step forward especially in terms of balance: engineers seemed to have found the right parameters that made the car enter its optimal operating window, as the SF-25 showed very good performance in the high speed corners also thanks to the very strong front-end, while suffering a little bit more in the medium and slow speed corners, where it was McLaren that made the difference thanks to the great downforce generated especially by the bodywork. From this point of view, Ferrari seems still to be a step behind (in terms of peak downforce), but the car seemed much more drivable than in Australia, with Hamilton particularly strong especially in the 1-2-3 complex, where he showed a very clean and precise driving. 

Moreover, the SF-25 seemed to work great especially on the soft tyre, as it was able to warm it up quite comfortably (also thanks to the relative hot conditions). The car was also very close to the ground in terms of ride height and with a very good balance in the high-speed. As shown by Leclerc, the car still lacks a bit of performance in the slow speed and medium speed corners, where they lose a lot especially in the second half of the corner (from apex to exit), where McLaren seems to have a big advantage. This weakness was underlined by Leclerc himself in Thursday press conference, as he explained that: “Low and medium speed seems to be the area where we need to work on a little bit more for now.”

The biggest question mark for the weekend will be the race pace, especially because Ferrari seemed to be a step behind the Woking-based team's cars this morning, but the Sprint will for sure give us a clearer idea on in that regard, but taking into account that after that short race teams will be able to make changes on their cars before qualifying. 

For what concerns McLaren, as it was previously said, they looked as the strongest team for the whole day, but a big opportunity was wasted during the SQ3: the team decided to go out very early and adopt a Push-Cool-Push strategy which didn’t pay off. The soft tyre, in fact, usually gives the maximum grip at the first attempt, which was the one did with a higher fuel load. Despite this, both Norris and Piastri were able to improve their lap times and setting bests sectors during their second run, proof that the MCL39 is a very complete car that is able to babysit the tyres not only through the single lap but also over multiple laps, something that other teams struggled with in FP1 on the softest C4. 

However, the drivers had some sort of issues with the car, as Norris complained that the wind was making the MCL39 a little bit unstable: “No, I think just throughout the day we've been struggling a bit with the front locking and struggling a lot in the last corner with all the tailwinds. So kind of a lot more aligned with Bahrain, say. Just a lot windier. When the wind's blowing, then we struggle a lot more.”

Despite this little inconvenience, the British driver had all the potential to aim for a better position in qualifying: during his first and only run in SQ3 (he aborted the second lap due to a mistake in Turn 14) he set a lap time slower than the one he set in SQ2 on the medium tyre. Comparing that to Piastri, he improved by 0.433 seconds compared to his lap on the mediums in SQ3; if Norris had the same improvement he would have set a lap time of about a tenth quicker than Hamilton’s quickest time. 

The impression is that the MCL39 has a higher potential than other cars especially in terms of race pace, but it’ll be quite difficult both for Piastri and Norris to get back to the top tomorrow morning in the Sprint, conscious that they’ll have to race against drivers like Hamilton and Verstappen (who locked out the front row), which can make their comeback particularly hard. 

Verstappen magical in the car, Merecedes struggling with grip

Coming now to Verstappen, the Dutch driver completed a fabulous performance once again: analysing the performance of the RB21 throughout the day, it showed Max's excellent performance in the last sector, characterised by the long straight. The team, in fact, adopted the same rear wing Verstappen used in Australia, which is a medium-low downforce spec (green arrow) but matched this time with the double element beam wing seen during testing in Bahrain (orange arrow). The goal was to give Verstappen a car with a very strong front end and with a low downforce set-up, conscious that the hot temperatures and the high grip offered by the new asphalt would have been a big help for him during qualifying, compensating for the lack of downforce. This choice could, however, be a weakness during the race, as it’d mean a higher tyre degradation. 

That’s exactly what happened during the Sprint qualifying today, with Verstappen quite positive about the balance and the performance of the RB21: “The balance was not massively off. We were just too slow but this is good for us, a little motivation boost for everyone […].”

On the other side of the garage things weren’t properly going this way, as Lawson was 20th in qualifying and therefore eliminated in Q1, denouncing some inexperience on a very technical circuit. 

Last but not least, Mercedes performance seemed to go a little backwards as the day progressed: during FP1, in fact, the W16 was running a very aggressive ride height, being very close to the ground and thus generating a high level of downforce from the Venturi channels. Moreover, they showed a very good performance both on the medium and on the soft, but as soon qualifying started, they seemed to struggle a bit more, with Russell complaining of no grip on both axles with the medium tyre. Things went a little bit better with the soft tyre in SQ3, but still far away from Ferrari, McLaren and Verstappen. 

The Achilles heel of this car still seems to be the race pace, as they were struggling a lot with blistering and thermal degradation during the simulations did in FP1 on the medium tyres.  

This said, it’s only the first day of a weekend which is set to be very long and exciting, with the Sprint ahead that will give us a clear idea on the performance of the top 4 cars in high fuel configuration.