A new chassis, new front and rear suspension, new gearbox and honed aerodynamics and sidepods will be the most visual changes to its heavily revised challenger.
In Formula 1, though, the devil is in the detail, and it will be in areas nigh on impossible to spot – like the underfloor, its aero platform concept and its ride height – where the biggest revolution will have taken place.
For the true story of what Mercedes got wrong with its previous two ground effect cars was not about topics that become major talking points – like its infamous zeropods or the seating position of drivers.
It was far more related to concepts relating to ride height – something that you cannot really observe from the outside.
As Mercedes technical director James Allison explained: “We placed value on the wrong things.”
The Goldilocks answer
Mercedes' issues can be traced back to the horrendous porpoising that its W13 suffered from in 2022, with a car that delivered its peak downforce in an area so close to the ground where bouncing became a problem.
However, lifting the car did not help much as it found itself losing too much performance, backing itself away from low ride heights.
It eventually got on top of the issues at play and did stage a good recovery throughout that campaign to find downforce higher up, winning the 2022 Brazilian Grand Prix, and that gave it some confidence that the worst was behind it.
Heading into last year, though, the enforced raising of the floor edges by 15mm meant that there was a critical decision to be made.
As Allison explained: “There was a big debate internally: should we cash in that 15mm and drop the car down, operate in a window that's 15mm smaller because the cars will be less bouncy inherently? Or should we do more of what has done us well over the course of the [previous] year, which is force ourselves to keep looking for downforce where it's difficult: high up?
“The debate raged internally for a while and the logic was sort of like this: it's very hard to predict, because the tools [F1 teams can use] are not especially good for this, where bouncing is going to be incurred.
“It's much harder to back yourself out of having driven off the end of a cliff and finding yourself bouncing, than it is to be too high, not bouncing, and then lower yourself towards it.”
Mercedes duly took the conservative approach and opted to chase downforce higher up, believing that rivals which opted for that extra 15mm would be at far greater risk of the dreaded porpoising.
“As it turns out, it was too cautious,” added Allison. “It was possible to cash in the 15 millimetres. We would have been better placing our chips on that part of the roulette wheel and we would have got much sooner to the sort of performance we were at [at the end of the 2023 season]. But, you know, them's the breaks….”
With stable regulations into 2024, Mercedes will be targeting a Goldilocks aero platform for its W15: not too low, not too high, but just right.
Downwash sidepods were 0.2s slower
The dominance of visual aspects serving to frame judgement over differences in car performance inevitably meant much debate on Mercedes’ car design revolved arounds its unique zeropod philosophy.
With Red Bull so dominant using its ‘downwash' concept, Mercedes found itself with too much emphasis being placed on its struggles being linked to the part that looked the most different.
There was an element of that view being reinforced at last year’s Monaco Grand Prix when, as part of a concept revamp for its W14, Mercedes elected to follow the downwash route.
Mercedes has been insistent since the start of 2022 that the sidepods were not a major factor in why it was not quick, and interestingly, Allison has revealed that changing philosophy actually hurt it in the short term.
Speaking about the move away from the zeropods, he said: “The change to the sidepod fronts were: let's just not have that as a thing to worry about for the future.
“And actually, as part of the overall package of things we put on that car there and then [at Monaco], the decision to go to that new sidepod front probably took about two tenths of a second off the update package we put on the car.
“But [it meant] we would at least know, from that point forward, that we don't have to fret about that.
“After a pretty torrid 14 months, we could just take that off the table as a variable, although actually that particular change on that particular day was slower than what preceded it.”
The 0.2-second deficit between the sidepod philosophies in Monaco may suggest that Mercedes could seek to regain such a leap by going back to its zeropod design, but that’s not the case.
The current generation of cars relies on all its aero surfaces working together and, as development of the downwash concept has moved on, so too has Mercedes regained all it lost initially. It was one step back for two steps forward.
Allison added: “The things that brought performance were all underneath the car, plus rear brake drums and rear brake ducts, front wing.
“But subsequently you work with what you have got then, and just iterate from that point. This car has long ago left that 0.2s deficit behind it. And away we go.
“The conceptual change was all about undoing the conservative decision about the ride height.”
Seating position
One of the other most public aspects of the car that became a talking point last season was the seating position, with Lewis Hamilton in particular feeling it had been a factor in his difficulties.
Speaking earlier this year, the seven-time world champion said: "I don't know if people know, but we sit closer to the front wheels than all the other drivers. Our cockpit is too close to the front.
“When you're driving, you feel like you're sitting on the front wheels, which is one of the worst feelings to feel when you're driving a car.
"What that does is it really changes the attitude of the car and how you perceive its movement. It makes it harder to predict compared to when you're further back and you're sitting closer, more centre. It's just something I really struggle with.”
This seating location is an obvious aspect that Mercedes could change for its W15, but Allison thinks that the complaints about the position was a consequence of other problems, rather than a cause.
He says the real issue at play was turn-in instability that both drivers have complained about, and if that factor was removed then the seating position would not really be a problem.
Allison said: “Lewis's way of expressing that is in talking about his seating position. George doesn't ever talk about his seating position, but he describes exactly the same ugliness to the car.
“If we could fix that [instability] properly, the only part of Lewis's seating position that he would still dislike is that he sees a bit less of the corner apex because he's a bit nearer the tyre than if he was a bit further back.
“But the actual seating position itself is not giving rise to a perceptual issue that makes it hard for him to detect how to handle the car.
“Possibly, if he was sitting exactly where he wanted, he might be able to drive a truculent thing with slightly more precision. But the issue there is get rid of the truculent thing, not optimise his seating position to handle something that isn't good.
“Our focus has been on making it less horrid. And I would say that the Austin upgrade [last year] was a mild step forward in that regard. And with a bit of luck, the [2024] car will bring a load more.”
