Antonelli and Russell head into Sepang blind as Pirelli relies on 2017 data

Formula 1 returns to the Sepang International Circuit for the first time in nine years to host the Bahrain Grand Prix, which could not take place in April. Only 10 weeks have passed between the announcement of Sepang's return on 26 July and race day on 4 October.

That short timeline hit Pirelli hardest. When F1 goes to a new or returning venue, the tyre supplier usually sends staff to map the circuit in advance, and that work forms the basis of its compound choice. This time, the Italian company simply did not have the time to do it.

Instead, Pirelli built its plan on what it learned at the last Malaysian Grand Prix. "Since 2011, I think we went all the years, so we have a good history," Pirelli head of motorsport Dario Marrafuschi said.

Marrafuschi explained in July that 2017 was the most useful reference point. It was the first year of the wider tyres, and he felt the balance between tyre size and car package back then was reasonably close to what F1 has today.

In 2017, Pirelli brought its medium, soft and supersoft compounds, which match the C2, C3 and C4 in today's C1 to C5 range. That is exactly the trio it announced on 27 August, labelled Hard, Medium and Soft. Because of the tight schedule, the tyres were also due to be sent by air rather than by sea, according to F1LivePulse.

The selection is one step harder than the C3, C4 and C5 used in Baku and planned for Singapore. Pirelli says leaving out the hardest compounds should bring one-stop and two-stop strategies closer together.

The track surface is the other unknown. Pirelli describes the asphalt as particularly abrasive and says it has not been resurfaced since F1 last raced there in 2017. Also, the section from Turn 6 to Turn 12 was resurfaced in 2023, with extra work around Turn 9.

In its preview released on Tuesday, Pirelli says Sepang puts medium energy through the tyres, in the same severity range as Spa-Francorchamps and Shanghai. It also names thermal degradation as one of the key variables of the weekend. The weather could make things harder still, as GPblog reported.

The timing is tricky for Mercedes. The team held back its first major W17 package since Canada for this race, as GPblog previously reported. "The updates [are] going to come from Malaysia onwards," trackside engineering director Andrew Shovlin said.

Mercedes won in Baku without new parts. Russell took pole and beat Max Verstappen to the flag by 0.196 seconds, while Antonelli still leads his teammate by 66 points.

Before Baku, Antonelli said Sepang would show whether the W17 still suffers from high tyre degradation and overheating on abrasive circuits. He hopes the extra downforce from the upgrade will help with that.

Teams have no recent race data, and the tyre choice rests on a nine-year-old reference and the first practice session to show how much the old surface has changed.