Sauber was really struggling in Bahrain pre-season testing, or at least that is what the laptimes and trackside impressions told us, so early improvements were critical for that team to get its 2025 Formula 1 season off to a reasonable start.
There are a couple of visual changes, but I’m pretty sure there will be more under the ‘bonnet’ of this revised car, which looked much more competitive in the hands of Nico Hulkenberg during Friday practice in Melbourne.
Again, as I often say, it all starts at the front - and what comes along behind has to cope with that front wing trailing edge flow structure.
Starting with version one, which was used early in pre-season testing, I have highlighted the trailing edge in yellow and red. The red is where Sauber has a gurney flap fitted to that trailing edge. The trailing edge is fairly ‘wavey’ - which is something that I’m not a fan of.
The second version (again with the same colours for illustration) was used on the last day of pre-season testing and early in Australia. With this one Sauber has created a more uniform trailing edge.
The third version, which was used for the second free practice session in Australia, has again a ‘wavey’ trailing edge, slightly different from version one but it also looks like the slot gap between the second and third element (highlighted with the magenta line) is now a little more ‘wavey’.
The trailing edge ‘trim line’ can be altered to suit the span wise loading, so it wouldn’t surprise me if this reduction in the chord length just inside the front tyre was to reduce the front wing work load in that area - especially when steering lock is applied.
On the other side of version three you can see where they have been using flo-viz paint to look at the flow on the wing surface. I have highlighted that flow with the small white arrows. It shows it being fairly uniform, even if it does fan outwards as you go outboard.
It’s critical to the performance of the underfloor that the flow coming off the inner third of the wing span is consistent, especially when steering lock is applied. With the wheels straight ahead, balance is not critical - it’s when you apply steering lock that consistency is the prime mover.
Sauber has also added a small fin (highlighted in magenta inside the red ellipse), which is on the outer lower edge of the radiator inlet.
This will help manage the airflow spillage that goes around the radiator inlet and reduce its effect on the sidepod undercut at high speed.
When technical director James Key was asked about Sauber’s transformation from pre-season testing to Melbourne, he gave an answer I think sums up how critical it is to get the best from the underfloor at both low and high ride heights. As we often say, everything is a compromise.
“These cars, the floors are so hard to push now that to replicate exactly what you're going to get when you're looking at structures beginning to let go a little bit at the very low ride heights, and then at the very high they tend to tail off - exactly where those peaks and the width of your aero maps is not a million miles off, but it always needs tuning, because you're talking half a mil[limetre] here or there," Key said.
