TECH CORNER: How did Sauber achieve its unexpected improvement?

On the back of their best race of the opening part of the 2025 F1 season, F1Technical's senior writer Balazs Szabo explains how Sauber updated their C45 for the Spanish Grand Prix.

Sauber made a good impression at last weekend's Spanish Grand Prix. Gabriel Bortoleto displayed eye-catching pace in qualifying, securing 12th place on the grid for the Barcelona race.

His team-mate Nico Hulkenberg usually excels in qualifying, but he was unable to extract everything from his car on a single flying lap in qualifying at Barcelona. However, the German racer made a brilliant start, picking up a handful of places to climb into the top 10 after starting P15.

Tbe Emmerich-born driver ran in P10 for much of the race, and was looking good for a championship point. However, he could capitalize on the late safety car intervention, picking off Racing Bulls' Isack Hadjar before also out-dragging the Ferrari of Lewis Hamilton down the straight.

Hulkenberg came home a brilliant sixth, but he was then later promoted to P5 due to a time penalty for reigning champion Max Verstappen.

"Right from the beginning, we were in the mix — a strong start, a clean first lap, and we were immediately able to fight for points. Ironically, not having the best Saturday and saving a set of softs gave us a strategic edge with the tyre allocation.

"The Safety Car mixed things up a bit, and having those fresh compounds turned out to be a golden ticket. There was a significant delta between used and new tyres today, so that really paid off.

"I didn’t quite maximise things [in qualifying]— it was disappointing to underdeliver, and I was frustrated with myself. But that anger gave me an extra push today. It’s satisfying to bounce back like this and bring home 10 points. Big result for us, that’s what matters in the end."

Following a difficult season in 2024, Sauber made improvements for the start of the current championship, and they managed to raise their competitiveness further by introducing a host of upgrades at the Spanish Grand Prix.

The Swiss-based outfit that will be Audi's works F1 team next year brought three performance upgrades to the Circuit de Barcelona-Catalunya. The Hinwil-based outfit debuted a new floor, front wing and engine cover at the last venue of the first European triple header in 2025.

The green outfit made a number of tweaks to the floor, introducing changes to the fences, floor edges and the diffuser.

Furthermore, the C45 featured a new engine cover at Barcelona, with the team having made alterations to the sidepod profile to work with the floor.

In addition, a new front wing was also introduced, featuring new end plates designed “to improve outboard front wing performance” and “better downstream flow quality”.

Confirming the positive effect of the upgrades, Hulkenberg said: “The car felt good all weekend, and the updates clearly gave us a step forward in performance — we had strong pace throughout the race.

"Credits to the whole team, both at the factory and trackside, for the hard work on the upgrades," concluded the German driver.