Unlike the regulations for the Grands Prix themselves, there is no requirement for the drivers to make a pit stop during Sprint events, yet in Saturday’s Sprint in Austria over half the field did so to try to gain an advantage over their rivals.

    In this week’s Strategy Unpacked, former Aston Martin strategy chief Bernie Collins examines who was right to pit, who should have stopped earlier – and who should have stayed out on their original tyres…

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    The Sprint race on Saturday was only 24 laps in duration, and therefore easily possible to complete on one set of medium tyres in a straight race to the flag without any pit stops.

    However the Austrian weather had other ideas. Rain before the race and light rain continuing at the start resulted in all drivers starting on the intermediate tyres. Valtteri Bottas attempted the formation lap on the medium but quickly aborted and dived into the pits before the start to swap to intermediates.

    So with drying track conditions the question for drivers and teams to answer was: should they switch to dry tyres and when?

    Of the 20 cars on track, 11 choose to make the jump to dry tyres in the closing laps. The first was George Russell with nine laps to go, and the last included Charles Leclerc, Alex Albon and Yuki Tsunoda with six laps to go.

    AUT S Tyre Stints.png
    Tyre stints chart for the Sprint

    In the closing laps Russell’s lap times on dry tyres showed that it was a much faster tyre. The problem for the others was, would there be enough laps remaining to make up the pit loss of 20.5 seconds?

    So how and why did Russell decide to jump first?

    Russell stopped from P11 stuck behind a train of cars that included Albon, Esteban Ocon, Lando Norris and Leclerc. However a pit stop would drop Russell to the back of the field with potentially nine cars to overtake to be back to the same position.

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    In these changeable conditions the communication between pit wall and driver is vital. Russell had initially commented that it was hard to read the track.

    “The problem is there is so much spray at the moment, I don’t know if the line is dry or its raining or if its just spray,” he says.

    SPIELBERG, AUSTRIA - JULY 01: George Russell of Great Britain driving the (63) Mercedes AMG
    Russell was the first to decide to come in and swap his intermediate tyres for slicks

    His engineer tells him it is not raining and later he says: “It’s drying quick so I don’t think its far off slicks.”

    “Yes but we want to be ahead of these guys if we want to box,” comes the reply.

    “If this was qualifying now I’d be boxing for slicks,” he adds.

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    In the meantime the pit wall would have been carefully monitoring the improvement in lap times for the entire field, as well as the weather radar, and Russell’s tyre temperatures, which are a good indicator of overheating and how suitable each part of the track is for dry tyres.

    The chart below shows the lap time improvement of the field. All lap times are reducing towards the green horizontal line that indicates a lap time suitable for a dry tyre.

    AUT S Crossover.png
    Tyre crossover chart

    With Russell jumping onto a soft tyre first it provided the other teams with very valuable data to work from. In the crossover chart above it is seen that Russell’s initial laps were only marginally quicker – however the GPS overlay tells a more detailed story.

    The chart below shows Russell’s speed around the lap on exiting the pit lane on the soft tyre (red), versus the lap before pitting on the intermediate (green).

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    It shows that in most corners Russell’s speed matches across both tyres. Where the soft is slower is on the straights, or the final few corners where the track is still wettest.

    This shows that already the track was very close between both tyres and that the soft would only improve relative to the intermediate as the track continued to dry.

    RUS S L14 L16.png
    Speed trace overlay for Russell between intermediate and soft tyres

    Russell’s early-stop lap allowed him to undercut two drivers – Leclerc and Albon – as well as close the gap and overtake Lando Norris. Russell raced Esteban Ocon to the finish line, ending the race just 0.009s behind in a photo finish.

    The outcome for others was strongly correlated to how quickly they followed Russell’s lead with the balance between drying track and laps remaining on a knife edge.

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    Oscar Piastri stopped one lap later than Russell and managed to undercut two cars and overtake three more to finish a full five positions ahead of where he was before pitting.

    Nico Hulkenberg, Lewis Hamilton and Kevin Magnussen all stopped two laps after Russell and managed to return to their original position. All would have benefitted from stopping one lap earlier.

    Russell explains why he was the first to make the call to pit for slicks in the Sprint
    Russell explains why he was the first to make the call to pit for slicks in the Sprint

    Stopping sooner would have given Hulkenberg the opportunity to attempt an overtake on both Aston Martin drivers to finish P4.

    Whereas Albon and Leclerc, who stopped three laps later than Russell, lost to those that had stopped earlier – and ran out of time to close the gap to those around that had stayed out.

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    For these drivers stopping so late was the worse possible outcome. In Albon’s case remaining on the intermediate tyre would have gained him six positions!

    Rarely in drying conditions with relatively easy overtaking is the pit stop lap such a fine line between success and failure, but in the Sprint format with its shorter time frame, every lap on faster tyres counted to the finish line.

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