F1 | Allison: “The W15 has correlation problems and suffers from the heat”

The start of the season has presented many more challenges than expected at Mercedes. After an overall positive opening GP in Bahrain, net of the overheating problems, with good performance partly due also to the favorable characteristics of the track, the limitations of the W15 emerged in the other two events.

However, if in 2022 and 2023 there was the awareness of having to deal with a project with several underlying problems and with fewer rival teams in the leading group, on the contrary the Brackley team had started 2024 with the hope of having solved some of the underlying problems that had undermined the two previous projects.

In part the feedback from the drivers was listened to, who had often complained about the unpredictability of the W14 and the poor feeling with the rear, in part the team almost went by exclusion, working on those elements that were thought to be the causes of the difficulties encountered in previous projects. Although the W15 has so far proven to be an easier car to manage for both Hamilton and Russell, it has not yet delivered the expected performance.

In Bahrain, the many slow and medium-speed corners had meant that the gap from the top was smaller, because the car expresses itself quite well in those sections, as was also seen in Australia. The greatest difficulties could be seen in the very rapid changes of direction and in the very fast corners, where the W15 had instead shown a lack of load and grip.

Those same problems then naturally arose again in Saudi Arabia, the fastest route of the three faced so far. Particularly in the fast sequence of the first sector, the car was unable to keep up with its rivals. To try to gain load, as had already been seen in Bahrain, an attempt was made to lower the car, but this triggered those annoying bounces at the rear which took away the drivers' confidence. In fact, the lack of grip and the bouncing created a disastrous combination for Mercedes' hopes.

According to technical director Allison, a trend has now emerged where the team is less competitive in hotter conditions. The latest data was the gap in competitiveness between the third free practice in Australia and qualifying: “We are starting to see a pattern that leads us to have moments of the weekend in which we feel confident in the performance and behavior of the car, and then find ourselves in other sessions where we don't find the same sensations,” explained Allison.

“If we were to try to reconstruct this pattern, what we can probably assume at the moment is that our competitiveness drops when the track is hot, and therefore the tire temperatures rise along with the asphalt temperatures. This gives us clues as to what we need to do from here forward”.

James Allison, Technical Director, Mercedes-AMG

Photo by: Steve Etherington / Motorsport Images

From FP3 to qualifying in Melbourne there was no change in set-up, which is why Mercedes believe it is an issue linked more to temperatures. From a certain point of view, however, it is also normal that as temperatures vary there is a specific window in which the car performs better and it is not unusual to hear of cars that express themselves better in certain conditions.

“If you have correctly identified why our performance varies, then you can work over the weekend with a dedicated program to improve the balance and find a better balance of temperatures between front and rear, using all the car's tuning tools “Allison added.

“This work can be done here in the factory, with simulation tools and things like that. But if, having reached the limit of what can be solved simply with setup changes, we come to the conclusion that it is necessary to go further and then becomes more difficult. In this case, one can think that there are underlying characteristics, for example in the aerodynamic map of the car or in the characteristics of the suspension, which aggravate that particular characteristic.”

“To ensure that the problem is solved optimally, you need to change these characteristics. It can be a simple operation, but in reality it can also become very complex.”

Photo by: Mark Horsburgh / Motorsport Images

After the last Grands Prix, Toto Wolff explained that the latest indications suggested that there were correlation problems between the data from the simulator and that obtained on the track, which is why the development work is even more complicated. If the data is misaligned, then even the simulation tools in the factory become unreliable, removing from the equation a fundamental tool in the design and development of the single-seater. Now James Allison is also on the same wavelength, despite the fact that after the tests, although held on only one “friendly” track at the W15, the British engineer had indicated that the data between track and simulator matched.

“There are always correlation problems in every year and in every team. There will always be correlation problems between what you see in the factory and what you see on the track, because the simulation tools are a sort of scaled-down version of reality.”

“It's not the same as driving a car on a real track, with all its infinite details and complexity. Here in the factory there are simplified models and these models help direct the work in one direction or another But all models have their flaws and all teams have correlation problems to some extent. The devil is always in the details,” added Allison.

“As regards the balance in all types of corners, from low to high speeds, we could improve our models, because we found differences between what we see on the track and what we see with the simulation tools. If we can reduce these different, then this will allow us to be more precise in the projections we make at the factory and take steps forward by solving those problems that are negatively affecting the car's performance.”