McLaren's principal race engineer Phil Prew has revealed that the team went into the Chinese Grand Prix with the intention of making only two pit stops.
Lewis Hamilton took his first win of the season after taking advantage of a three-stop strategy to outperform Red Bull rival Sebastian Vettel, who stopped only twice. Hamilton's three stops were crucial to the Briton catching and passing Vettel for the lead.
McLaren, however, decided to stop three times only during the course of the race, with Prew admitting the initial plan was to make two stops.
"There was an awful lot going on," Prew said. "And a great deal was changing through the race, depending on tire choice and how the different cars used their tires and how the drivers used the tires as well.
"We were working out how the tires were going to behave, and how long they were going to last, once we'd established that, once the drivers were giving us feedback about tire performance, that dictated very much our strategy, and that's when we adopted the three-stop. We went into the race truly not knowing what we were going to do. If the tires had kept going, then the two-stop might well have been the fastest strategy. But for us we made the decision that it wasn't, and we adopted the three-stop."
He added: "Overall we went into it with a clear two-stop intention, which I think a lot of people did. We adapted to three stops just in time, because we could see tire degradation was going to be significant, we didn't think we could safely do two stops, just looking at what other cars were doing."
McLaren boss Martin Whitmarsh revealed that Jenson Button's mistake during his first stop – when the Briton stopped in Red Bull's pit slot – was more costly than initially thought. Whitmarsh also said Button should have stopped a lap earlier, something that cost him and Hamilton valuable time.
"It cost Jenson position and it cost him time," said Whitmarsh. "Within the stop itself it cost over two seconds and it cost a position, the fact that he stopped a lap later than he should have done as well cost him time, and it cost Lewis time and it cost Lewis track position as well, in that last lap was when Massa got by and he should have stopped by then.
"It was pretty calamitous, simple way of looking at it, we were first and second and we were whatever fifth and sixth [actually seventh] after the first stops, so at that point we knew we had to do something different. That partly prompted the view that we had to change strategy. In the end, that would be the right way to go."