Why did single stop work in F1 Belgian GP? Pirelli provides explanation. Mario Isola's comments on pit stop strategy in Belgium GP.

George Russell, the masterpiece denied
George Russell’s gamble to stop only once in Belgium had paid huge dividends, but technical checks revealed that his Mercedes W15 was 1.5 kg underweight.

For the British driver, disqualification was inevitable. A disqualification that erases the final result but not the strategic masterpiece created by the Mercedes driver, the only one at Spa-Francorchamps who chose to go for a strategy with just a single stop. Of course, George Russell was in a position to take such a risk – with equal stops he would have only fought for the top-5 –, but this risk had to be taken first (Carlos Sainz, for example, had little to lose by going much longer in the first stint) and then it was worthy of consideration, as the track conditions had changed significantly compared to race-pace simulations from the first two free practice sessions on Friday.

Mario Isola’s comments
Pirelli, which before the Belgian Grand Prix had not even considered the single stop as a possible strategy, explained through motorsport director Mario Isola why George Russell’s choice paid off on track: “On the eve of the race, we had stated that a single stop would not be a convenient choice because it was not fast enough compared to the double stop, but Russell’s performance – aside from the subsequent disqualification – appears to contradict the predictions,” he commented on Pirelli channels.

“To try to give a first explanation on the spot, at least from the point of view of tire behavior, we can highlight a few factors. First of all, there were about ten more degrees on the track surface during the Grand Prix compared to the second free practice session, which probably helped to greatly limit the graining that had been very significant on the mediums during the long runs. Furthermore, we can hypothesize that the teams worked hard on the setup of the cars, both to find the right compromise between a wet qualifying and a dry race and to try to protect that front axle more susceptible to graining. A third element to consider is that many drivers managed their stints on the mediums very carefully, especially in the faster corners.” – Pirelli’s Mario Isola explained at the end of the Spa-Francorchamps race.