Mercedes is rolling back the rear suspension Formula 1 upgrade it debuted at Imola in a bid to find the reason behind its 2025 performance drop-off.
The team has comfortably been the weakest among F1's top four since the start of the Europe-heavy leg of the season, with its only podiums - a grand prix win and a third place - coming on an anomalously strong Montreal weekend.
The otherwise-poor run of form coincided with the troubled introduction of its new rear suspension at Imola, a part it dropped for Monaco and Barcelona because both its drivers struggled with balance issues.
The suspension upgrade returned for the team's standout Canadian Grand Prix weekend and continued through Austria, Silverstone and Spa but it has now been dropped again for this weekend’s Hungarian GP.
The upgrade worked well in Montreal, but it has been particularly problematic in high-speed corners in the following races.
Kimi Antonelli in particular has struggled, with his third place in Montreal his only points finish at the last seven events.
"Montreal is a very special track, grip is very high, Tarmac is quite closed," said Antonelli. "But at the end of the day Montreal is all straight line braking and then the chicanes, which are all about setting the car up nicely for the first part, and accelerating for second.
"[So the] new suspension was really good for straight line braking and combined traction - really good combined traction phase - so that was best for Montreal.
"That's why we were so strong, I think that was main thing. Montreal is such a special track and really good for our suspension, mainly because we had no real combined corner at high speed."
The F1 rookie admitted at Spa last weekend that he was facing a confidence crisis, with his driving exacerbating the limitations of the Mercedes W15, hence his relative struggle compared to team-mate George Russell - who has scored 64 points to Antonelli's 15 over the last seven race weekends.
Now Mercedes has rolled the rear suspension back on both cars to a specification used prior to Imola.
"This weekend we're going back on the old suspension and that will hopefully bring the feeling back. Since we moved to that suspension, apart from Canada, I've been struggling to drive the car and get the confidence," Antonelli explained.
"Probably also my side I didn't adapt the best because I was always trying to keep my style and to drive the way I wanted but it didn't really work out. George on the other hand has been adapting better, also has a different driving style, also being able to adapt better.
"That's what has been hurting me in the European season. Hopefully going back to old suspension, it will bring back the feeling I had prior to the start of the European season."
Antonelli said his more aggressive style was "making the car even more unpredictable" and he also berated the way he'd adapted to it.
"If you have the confidence and you know it's going to stick it, it can really make a difference, but in my case, especially with the style I was just making it more unpredictable and having no confidence," Antonelli explained.
"Every time I was trying to push more, the car was struggling to take it or was giving me signals that made me feel like it wasn’t going to stick.
"So that's why I've also been trying to change the way I was driving, to go towards the car.
"I think I didn't do a really good job on that, I just hope that the old suspension is going to bring the good feeling back."
Russell said the change has "been on the cards for a little while" and was no different to what rival teams have done.
"It's part of development; we've seen it in other teams as well this season, they bring things to the car and you're looking for that last sort of tenth of a second, and you often see the gains, but before you put it on the car, you don't know what the limitations are going to be," Russell said.
"So there's no guarantee that's the reason why we've taken a step back. It could be a factor - we'll use this weekend to assess - but, if you just look at the results as a whole, we clearly have gone backwards and we need to go back to a baseline that we know."
Mercedes knows it's taken a misstep somewhere, rather than this poor form simply being a case of being outdeveloped by McLaren, Red Bull and Ferrari.
"It's a guessing game, complete guessing game, when you try to say what maybe other teams have done to improve themselves," technical director James Allison explained after Spa.
"But when you have a situation where seemingly everybody's improved by the same amount, everybody, and you've just slipped backwards, more often than not when that happens it's because you have made yourself worse by that amount.
"It isn't that everyone magically has put on the same size upgrade and crept up around you through that."
Mercedes held meetings with its drivers at its Brackley base in the days after the Belgian GP, with a promise to “pick off the most likely candidates” behind its slump and “get that sorted in Hungary".
