MCL39 v FW47: The big differences that separate McLaren and Williams

We’re just two car reveals down and have eight left to go but, given the different ends of the championship standings that the two teams occupied in 2024, it’s clear that’s had an impact on how they’re going to approach 2025.

That’s not a slight on Williams, it’s just the reality of a sport driven by multiple factors, some of which the Grove-based squad are still trying to improve in order to make that next jump up the pecking order.

MCL39 v FW47: Comparing apples and oranges

If we are to compare the two cars we’ve seen launched so far, it would be fair to say that McLaren have been able to add more weapons in their design arsenal, whereas Williams have been forced to focus on optimising those they had already been developing.

In this respect, the MCL39 has numerous design concepts that its predecessor did not, albeit most of those are solutions that McLaren have seen developed by their rivals and studied, refined and applied to their own car this season.

This includes the new P-shaped sidepod inlet arrangement, which we’ve seen multiple teams use last season, albeit with slightly different variants favoured by each, as they all look to target their own specific needs both from a cooling perspective and what will work aerodynamically with the rest of their package.

This also extends to the rear of the car, where McLaren have adopted solutions seen on the RB20 and SF-24, with a small outlet to be found behind the sidepod’s downwash ramp bodywork and feeding into the coke bottle region (white arrow), whilst a split line and depression arrangement can be found above this on the engine cover’s shoulder.

There’s also the new winglet that’s sprouted from the bodywork beside the MCL39’s halo, which is positioned similarly and bears some resemblance to features seen on last season’s Ferrari and Aston Martin.

However, whilst the team have clearly engaged in developing concepts well known to their rivals, there are some new features too, including the switch to a more oval-shaped airbox and the more aggressively inclined upper wishbone on their front suspension.

For Williams, it’s been more about optimising the design solutions that they introduced last season, whilst also accommodating the new crash structure, gearbox and rear suspension arrangement provided by Mercedes.

This year they’ll utilise the same hardware as the Mercedes works outfit and Aston Martin, with Williams developing an updated version of the push-rod suspension layout that was run by those two teams last season, rather than continue using the same rear end as they had in 2023, including the pull-rod layout.

This change has also likely precipitated the alterations made to their centreline cooling arrangement, with the saddle-style cooler that was a feature of the FW46 having to be moved elsewhere, whilst the exhaust tailpipes routing has also been modified to suit the inboard suspension element now being on top of the crash structure and gearbox casing (as seen on the Mercedes, right image, green arrow).

Those changes may have also led to the arrival of the mini T-wing that is mounted on the side of the rear wing support pillar, as that space has suddenly been exposed by the alterations to the engine cover and its rear cooling outlet.

And, whilst we haven’t seen this exact sort of solution during this regulatory era before, it’s unsurprising to see something like this appear, given the designers will often use any spare space within a legality box. Formula One’s former dalliance with the larger T-Wings is a prime example of this.

Williams might still have the same general design when it comes to their sidepods in 2025 but it has been quite significantly modified, with both the internal packaging and bodywork more effectively optimised around the characteristics first introduced with last season’s update at the Dutch Grand Prix.

In order to provide some development scope during the course of the season they’ve also redesigned the area of the floor around the SIS tube, which now sits higher within the bounds of the floor’s upper surface, allowing for more detailed work to be carried out on the floor fences and underfloor.

The team have also noted the development trajectory of their rivals, altering the design of their front wing and nose assembly for 2025. This includes switching to a more neutral chord distribution across the wing’s span, rather than the more centrally loaded solution used by them on this generation of cars.

Read more: Williams FW47 uncovered: The significant design clues from Silverstone