Ferrari project 677: the few benefits of rear push-rod suspension at the expense of compliance
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The Ferrari SF-24 featured a pull-rod rear suspension, with a tie rod instead of a strut. Rumors about an imminent switch to a push-rod rear suspension have been very persistent regarding the Maranello team’s new single-seater for the 2025 Formula 1 championship. According to various reports, the 677 project will essentially overturn the suspension layouts on both axles with new kinematics. These predictions are quite peculiar and, in all likelihood, misinterpret Frederic Vasseur’s recent comments on the Ferrari. Speculation suggested a shift to a push-rod rear suspension between 2023 and 2024, which ultimately did not happen.
Italian aerodynamicist Enrico Cardile, at the time, explained simply why it was not adopted. This makes it a good moment to delve deeper into what the former technical director asserted almost one year ago. First, let's start with a fundamental concept: switching to a rear push-rod suspension is an advantage, but not as significant as one might think. It is not enough to merely replace a tie rod with a strut, to exaggerate the concept. The benefit lies in achieving a cleaner airflow toward the rear, as the internal components are arranged higher, allowing for a slimmer lower section.
Already with the SF-24, Ferrari spent considerable resources in order to achieve a compromise between the two layouts, with excellent results. The “technical agreement” was reached by reorganizing the components under the car's bodywork, enabling them to function differently compared to the past. Furthermore, resizing these components as a whole made it possible to slim down the lower rear section. However, the tie rod remained, which still slightly disrupted the airflow in that specific area of the car.
It should be noted that Mercedes also switched to a push-rod rear suspension during the 2024 Formula 1 racing campaign. For several months, this change caused various adaptation issues. It was a suspension adjustment tested on track that found its proper operational point over time. This suspension modification will also feature on the W16 single-seater. Returning to Ferrari, evaluations conducted at the factory during the past season did not reveal a significant advantage in abandoning the pull-rod rear suspension to justify the added weight and reduced compliance.
Everything ties into the functioning of the floor, which, to operate within its optimal window, depends heavily on the rear suspension. Ensuring a certain conformity between these two elements is essential and inevitably brings several advantages. By "compliance," we mean the suspension system's ability to deform under load. This deformation is crucial in determining the accuracy of the aerodynamic map. It is also true that, with the updated wind tunnel, Ferrari's development work has appeared more consistent since the Las Vegas Grand Prix.
Unfortunately, the six races lost during the season due to technical issues weighed heavily, and for this reason, just as with the front suspension, switching to an entirely new suspension system would be a significant gamble for the Maranello team in the 2025 Formula 1 campaign. If the Ferrari engineers and technicians had decided to install a push-rod rear suspension, it would mean that the way the internal elements are activated would change, even if the kinematics could remain similar, with the upper and lower wishbones possibly retaining the same shape.
What could change in this case is the method of operating the third element, which regulates ride height—a critical parameter for the current ground-effect cars. It is by no means certain that on February 19 we might see some tweaks to the layout of the overlapping wishbones. If the goal is to recover some of the traction lost in 2023, it is necessary to achieve better ground contact and maintain it for a greater percentage of time during the acceleration phase. To achieve such a result, adjustments are made to the layout of the overlapping wishbones.
This is done by making small changes to the arrangement of the four arms, which can lead to significant differences in on-track behavior. A good compromise between compliance and suspension rigidity must always be found to achieve optimal floor dynamics. Furthermore, it is also possible to ensure that the bars used to achieve a good setup are less rigid by default. This aspect is not necessarily tied to the use of a push-rod system. Ferrari could make several mechanical adjustments without overhauling the entire setup.
This is why we do not expect a radical change, either in terms of the layout or the kinematics. It seems more likely that several refinements have been made to adjust both areas related to the rear suspension. These changes might not be immediately visible to the naked eye but are based on the technical understanding gathered in 2024, a move to optimize the performance of the new floor. This could be what Frederic Vasseur meant when he stated that only 1% of the Ferrari SF-24’s components would remain unchanged in 2025.
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