The Barcelona Grand Prix is behind us, along with a first significant portion of the 2025 Formula 1 season. A round that further confirmed the dominance of the McLaren MCL39, despite the arrival of a technical directive that was supposed to reset everything. As every year, the Montmeló track helped to reveal both the strengths and weaknesses of each car. The latter seem to be absent on the McLaren, with the secret behind its enormous advantage discovered exclusively trackside. A feature that, however, also brings some significant challenges, echoing Lando Norris’s remarks.
At last Sunday’s Spanish Grand Prix, we observed the behaviour of the cars through the numerous corners on the circuit. A tough test for aerodynamics and chassis alike. Stationed at Turn 9 during qualifying, interesting details emerged about the behaviour of the RB21, MCL39 and SF-25. As explained in the initial article, the differences are minimal, but in Formula 1, it’s the fine details that make all the difference.
Clear images from the 4.657-kilometre Circuit de Barcelona-Catalunya confirm a flat McLaren, which appears not to lean, unlike the Red Bull and Ferrari, which do so—albeit slightly. This behaviour was confirmed by sources from rival teams after seeing our photos and hypotheses. We are talking about a car with no roll, achieved through refined work on the internal elements and kinematics of both front and rear suspension.
At the heart of the issue is the concept of roll— that slight movement around the car’s longitudinal axis when taking a corner, accompanied by a lateral load transfer. This movement revolves around a virtual point called the “roll centre,” whose position relative to the car’s centre of gravity, also known as COG, has a major impact on cornering performance. If the roll centre is nearly aligned with the COG, as in McLaren’s case, the suspension barely moves at all.
The result is an extremely flat setup, with practically zero roll gradient, allowing precise control of ride height and keeping the diffuser consistently in its peak efficiency window. If lower, the suspension has greater travel and shows a slight hint of roll. This enables variable increases in aerodynamic load, as the rear lowers at the right time and channels more air through the diffuser.
The key work, primarily on the rear suspension, is the product of a refined interplay between internal kinematics and a superb suspension layout. Springs with progressive behaviour, stiffening as load increases, provide an extraordinary advantage. Soft at low speeds for traction and rotation, firmer and more reactive at higher speeds. In simple terms, the MCL39 corners as if it were on a straight. This allows the car to never lose downforce—something extremely harmful in high-speed corners or direction changes. It’s almost as if the MCL39 behaves like a go-kart at high speeds—but with vastly superior downforce.
Lando Norris was right about a superior, but not easy, McLaren.
The flip side of this coin is crucial. While the car is extremely fast and reactive during changes of direction, it also presents considerable challenges for the drivers. The earlier reference to load transfer is key here. When a driver feels the load shift, they know how far they can push the car—something the two McLaren drivers seem unable to do. Once the car reaches its grip limit, the slightest additional input results in a sudden loss of control, without any warning.
This explains why, in the early races of the 2025 Formula 1 season, Lando Norris was heard complaining about a car that, while fast, was very difficult to drive. This fully clarifies the situation and proves the work done by Rob Marshall’s teams has gone beyond expectations.
McLaren team principal Andrea Stella himself, moments after the podium, admitted something important. Alluding to the significant work on the rear suspension as the foundation of the car’s major advantage, the former Ferrari race engineer hinted that this analysis is on the right track. His words were later confirmed by F1inGenerale sources within rival teams, who also see the MCL39 as a car without roll.
This behaviour obviously makes it extremely fast and agile, but it is not enough to make the MCL39 a dominant car on its own. The combination of aerodynamics, thermal management, and other factors has created a highly effective machine. Perhaps, the mechanical level achieved is so refined that it even complicates the introduction of substantial upgrades—like the diffuser glimpsed at the Jeddah Corniche Circuit in Saudi Arabia.
