What's caused Sauber's terrible F1 pitstops in 2024

Sauber is not expected to have a definitive fix for the disastrous pitstop problems that have blighted it so far this season for another three or four races.

This means its results could continue to be heavily compromised until at least the start of the European season in May.

The team suffered from cross-threaded wheelnuts on the front-left corner in each of the first three grands prix of the season, with the delay suffered by Valtteri Bottas at the first round of pitstops in Australia costing him almost half a minute - and, consequently, throwing out a likely points finish.

Bottas had also endured a lengthy delay in the Bahrain season opener, with team-mate Zhou Guanyu stymied in Saudi Arabia.

The problem is understood to be related to the lightweight material used in the new-for-2024 wheelnuts that are part of the team’s winter investment in equipment and components designed to improve pitstop times.

The problem did not arise during practice ahead of the season, but is a result of building temperatures in race conditions. This makes it difficult to replicate outside of a racing situation.

Sauber introduced countermeasures for the Australian Grand Prix weekend that it hoped would eliminate the problem, even though this came at a time cost.

Even when the pitstops worked as intended, Sauber was the slowest at tyre changes in Australia. According to DHL, Sauber’s best pitstop of the race, Zhou's first after six laps, took 3.40s. By comparison, the fastest of the race was Red Bull driver Sergio Perez’s second stop, which took just 2.10s. That’s due to the countermeasures Sauber put in place intended to prevent the wheelnut problems.

Unfortunately, these proved not to be enough despite head of trackside engineering Xevi Pujolar having been “reasonably confident” after practice pitstops earlier in the weekend suggested there should be no problems in the race.

Slowest Australian GP pitstops (per DHL)

1. Zhou (Sauber) - 3.40s
2. Piastri (McLaren) - 3.51s
3. Bottas (Sauber) - 3.63s
4. Gasly (Alpine) - 5.04s
5. Ocon (Alpine) - 14.71s (tear-off in brake duct)
6. Zhou (Sauber) - 20.20s (car stalled)
7. Bottas (Sauber) - 31.18s (wheelnut issue)

These countermeasures will be retained for the upcoming races and made more stringent if possible.

“From the first race, we found some issues with the pitstops, with cross-thread [wheelnuts]” said Pujolar. “When we do free practice or even during the winter, we didn't find a problem but then every time we go into a race situation, it becomes more critical.

“We took some containment [steps] with this week some small modifications, but it's not robust enough and we had one pitstop issue.”

Pujolar confirmed that the parts requiring changes come from an external supplier.

The modified designs of the wheelnuts and the front hubs will take time to produce given the metallurgical processes required to manufacture them, hence the wait. The team is unable to revert to parts used last year because they are not compatible with the completely revised 2024 front suspension.

Sauber also had a delay at Zhou’s second pitstop in Australia, but this was an unrelated problem.

“The pitstop itself went OK,” said Pujolar. “It’s just that with that car we had a gearbox problem in the race that meant that when we went into the pitstop, it went into anti-stall. But it didn’t trigger properly and stalled the engine. It looked like we had a pitstop issue but actually that was not related to the pitstop itself.”

Sauber's best finish so far this season is Zhou's 11th in Bahrain. Bottas and Zhou finishing 14th and 15th respectively at Albert Park.