Sauber has been - on averaged 'supertimes' - the slowest car across the 2025 Formula 1 season so far.
Yet in Spain, Nico Hulkenberg was able to pounce on Lewis Hamilton at the final restart and beat the Ferrari to a remarkable fifth place.
Hulkenberg declared Sauber’s first top-five finish in a F1 race in three years "puts us more on the map in the midfield fight", reflecting the significant step made with the upgrade package for the Spanish Grand Prix.
Fortune played its part in Hulkenberg’s result as he was the only driver with fresh soft tyres available for the final stint after pitting under the safety car - allowing him to overtake Isack Hadjar as well as Hamilton before picking up another place when Max Verstappen was penalised.
But unlike in the Australian GP, where Hulkenberg finished seventh thanks to a well-timed switch to intermediates, he was already on course for points on merit before the race was transformed - and had moved up to eighth when Kimi Antonelli suffered an engine failure.
The improved performance of the car was clear. Gabriel Bortoleto qualified 12th, just 0.145s off the top 10 in Q2, while Hulkenberg was out in Q1 after the laptime fell away in the final part of his lap. Despite that, it was clear that the Sauber was, at a heavily aero-dependent circuit, at least a top-end of Q2 car and could have made it into Q3 with perfect execution.
The upgrade, which comprised a new floor, engine/'Coke bottle' section cover and front wing, was not about creating a significant downforce gain but instead to tackle a persistent problem of the Sauber C45 this year. As sporting director Inaki Rueda said ahead of Friday practice: “[On] peak downforce we’re not expecting a very big improvement, the biggest improvement comes from having a more driveable car.”
He went on to explain how the Sauber had become more peaky, which was particularly showcased by it being especially sensitive to turbulent air.
"It happens up and down the pitlane," insisted Rueda. "It’s very common that as you put downforce on, you get a more peaky profile. So you usually get to a point that you get a car that is decent, let's say, but is undriveable in tricky conditions.
"It is a point that was highlighted at the start of the season, on our first test with this car. And this is hopefully the fix for that."
Although this upgrade package coincided with the technical directive reducing the permitted front wing flexibility, adapting to that was only a small part of this package and, therefore, of the performance gain.
Rueda described the structural front wing changes to comply as only 10% of the upgrade. And although it is difficult to put an exact number on the performance step given the benefit of driver confidence can't be measured precisely in the windtunnel, Friday practice indicated it was a big step.
Then, Hulkenberg ran the new package while Bortoleto used the old specification in order to conduct a thorough back-to-back comparison - with the 0.367s gap between the two understood to be seen by Sauber as broadly representative of the improvement. That gap was compounded by the fact Hulkenberg was able to gain significantly in the final sector thanks to improved treatment of the tyres thanks to the more stable package.
While team principal Jonathan Wheatley was cautious about declaring Sauber's weakness in turbulent air to be a thing of the past after the race - arguing the car needs to run at more tracks to be sure - he did point out that "the pack was quite close today, cars were following each other quite closely". That suggests Sauber has delivered on its expectations of producing a less peaky car.
That’s significant because while it’s relatively easy to generate big downforce figures with these ground effect cars, doing so in a controllable way that doesn’t lead to such weaknesses - and that works across a wide range of corner-speed profiles - is not easy.
Barcelona was more a test of performance in quicker corners, so it remains to be seen how the upgraded car works on a track with more slow corners, but it’s clear that it is now less critical. That indicates a good aerodynamic understanding that bodes well for what Rueda called "another major upgrade planned for later this year".
The Sauber is, on average, the slowest car across the 2025 season but now holds eighth in the constructors’ championship. The Barcelona performance at least shows that there will be some weekends on which it can challenge for points on merit - and that’s a positive step for a team that has struggled badly of late.
"It’s huge," said Wheatley of the impact on team morale. “There's so much hard work goes on and there's so much passion in this team. I'm hoping that we can use this as one of the springboards that I talked about, on this roadmap we've got towards where we want to be. I'm hoping we can build on the momentum from this."
Gary Anderson's analysis
Sauber is one of the teams whose drivers have complained most about the car in turbulent or windy conditions. I’m pretty sure every driver thinks they are driving the worst car when it comes to not running in clean air.
However, if you just keep pursuing more and more downforce in a perfect windtunnel environment, it’s very easy to overwork the aerodynamic surfaces. Then, when you get to the track environment and encounter a little bit of cross wind or turbulence, those surfaces suffer airflow separation. The trouble is that any surface separation problems can have a compound effect further downstream.
The front wing Sauber introduced doesn’t look massively different. I have highlighted with the red double-ended arrow the Gurney flap section Sauber ran in Monaco and compared it to a reduced Gurney flap section it ran at Barcelona. I think this change is more or less circuit-specific, so other than stiffening up the assembly (which could very easily help consistency downstream) to comply with the new technical directive the FIA issued for Spain, I’m not seeing much change in this area.
It all gets a bit more exciting when we get to the sidepod treatment. Previously, Sauber simply had a sidepod top surface inner gully, highlighted with the red arrows running from the forward upper surface of the sidepod, leading down into the centreline of the car to help with the diffuser performance.
For Barcelona Sauber altered the outer 'rolled bathtub' edge and reduced it midway along the sidepod. This will allow some of that upper surface flow to spill over into the Coke bottle area, highlighted with the orange arrow.
This spillage will improve the consistency of the flow coming through from the sidepod forward corner undercut, highlighted with the blue arrows. If this airflow that is being pulled through that sidepod front corner undercut is not consistent, then everything can suffer - the front wing performance will suffer, the outer edge of the floor sealing mechanism will suffer and the extraction vanes further forward, which I have highlighted in light blue, will also suffer.
So for a small increase in overall downforce when the car is running in an ideal world it can very easily turn into a major loss of downforce when the car is running in what could be called its normal environment.
