Mercedes' decision to bring Lewis Hamilton in for a second stop ultimately proved the difference in Spain, and trackside engineering director Andrew Shovlin explained the thinking that went into the decision.
Although the Brit started the race on pole position, he saw that advantage go away heading into Turn 1 with Red Bull's Max Verstappen making his way past. As a result Mercedes were forced to rely on strategy to retake the position, bringing Hamilton in for a second stop.
In the end the move proved to be the difference, with Hamilton passing Verstappen in the closing laps to take his third victory of the season. Shovlin explained that the tyres were degrading at a faster rate than their simulations predicted, making the two-stop strategy the clear winner in their mind.
"The conditions were quite different to those that we had seen in Free Practice but from the runs that Lewis and Max were doing, we could see that the tyres were dropping and they were dropping a bit more than we expected from our pre-event simulations, where we actually thought a one-stop and a two-stop were very close in terms of performance," Shovlin stated in a Mercedes YouTube video.
"What we could start to see when we put that degradation and put it into our linear strategy tools was that the two stop was now coming out as a clear winner and the point that we actually decide to trigger the stop, that's the point where we are talking about calling the driver in and getting the pit crew out. But when we got into that second stint that was when we really started seriously thinking about making this happen."
Shovlin stated that even when the decision to make a second pit-stop was made, the exact time of it had to be considered as Mercedes wanted to make sure Hamilton had enough grip and enough laps to make a pass stick.
"We are checking the degradation, so we are making sure that Lewis can actually catch up on that other set, we are making sure that when he does catch Max he has got the pace to be able to overtake him and for a lot of that stint, we were actually just reviewing the optimum lap," Shovlin added.
"We knew it was somewhere in that 40 to 43 region and if we go too early, by the time he catches Max, his tyres haven’t got enough grip to be able to pass, if we go too late we haven’t given him enough laps remaining in the race to be able to actually catch and attack."