Lewis Hamilton and Charles Leclerc were present at the Mugello circuit for the Ferrari filming day on Thursday, July 17. However, the Maranello-based team had a new upgrade to the car for drivers to test, feel, collect data, and provide feedback about it. Reports have suggested that the upgrade expedited the team in the right direction and will be brought to next weekend's F1 race at Spa-Francorchamps.A new rear suspension has been in development for months at Ferrari, which was brought to the Mugello test by the team. Both Lewis Hamilton and Charles Leclerc tested the new suspension and gave their respective feedback.Ferrari has struggled with the ride height of the SF25 since the start of the season, which also led to Hamilton's disqualification at the Chinese GP, where the car ran too low and the plank wear was more than what the FIA regulates. Ever since, the SF25 has run a compromised setup to make sure the car didn't bottom out.This meant that the car was not able to run at the optimal height to generate the projected downforce, and also led to a compromised setup for the drivers. Leclerc and Hamilton reportedly ran setups with a stronger front end to counter the loss of downforce at the rear end, which led to struggles and spins.Nonetheless, the new upgraded rear suspension has reportedly made a step in the right direction. Sources suggest that the new suspension is a ‘significant’ improvement over its outgoing counterpart, and will be officially introduced by Ferrari at the Belgium GP.The new rear suspension, in combination with the upgraded floor brought by Ferrari at the Austrian GP, is said to give Lewis Hamilton and Charles Leclerc the competitive edge over Mercedes and Red Bull.What are the changes made to the rear suspension by Ferrari that were tested by Lewis Hamilton and Charles Leclerc?The new Ferrari rear suspension, tested by Lewis Hamilton and Charles Leclerc at Mugello, followed a similar ideology to Mercedes’ new rear suspension, where the front arm of the upper triangle was brought closer to the front.The Scuderia introduced a new, shorter gearbox, and the new rear suspension will further optimise the space around the gearbox, creating more room for the dampers, which in turn will help the car run lower and be more compliant under load.The front arm is brought towards the front, and the mounting points are lower than the previous suspension. This will not only help with the lap times but also allow Lewis Hamilton and Charles Leclerc to move away from the extreme setups and run the car in a wider, optimal window.