Mercedes has elaborated on the thought process behind the strategy call that left Lewis Hamilton berating the pit wall during his remarkable Monaco Grand Prix victory drive.
Hamilton spent much of the race questioning his team's strategy after an early pit stop on lap 11, forced on the leaders by an early safety car period. His car was fitted with the medium tyre to go to the end of the race instead of the more durable hard tyre.
The reigning world champion was concerned his tyres would not make the finish. Making matters worse was that the three cars right behind him -- those of Max Verstappen, Sebastian Vettel and Valtteri Bottas -- were all fitted on the hard option. Hamilton was able to withstand Verstappen's relentless attack until the end of the race to cling on for one of his most memorable wins.
After Hamilton did so, Mercedes strategist James Vowles opened up the radio channel to tell him no other driver could have taken the car to the finish on that tyre.
Vowles has now explained what led to that decision, saying it had roots in the data Mercedes collected during the practice sessions earlier in the week.
"The reality in Monaco is, you won't overtake, so even though we had the hard tyres ready in the pit lane to fit to the car," Vowles said in a Mercedes video released Thursday. "If we had to pit at any point, we would have just been fourth in that train of cars. You can't overtake -- you saw that with Max Verstappen trying really aggressively with Lewis.
"So perhaps the bigger question is, why did we fit the medium tyres to Lewis? To answer that we need to go all the way back to Thursday [practice]. We were one of the top teams to have both medium and soft available to long-run in the second practice session. The track conditions were slightly worse than they were going to be in the race but still representative enough to understand how the tyres would be performing.
"On the long run on the medium, we were able to see that their life would just about make what we needed to in the race to achieve the stints that happened when the safety car came out. That's what triggered our decision. In Monaco, you typically want the softest rubber you can get away with for the stint length that you're trying to get to. We knew it would be tight, we knew it would need a lot of management, but believed based on the Thursday that the medium tyre would do the job."
The threat of rain also complicated matters.
"If you could see our weather radar, you would've seen the sea of blue come in from the east towards the circuit," Vowles said.
"Now, it actually broke up. There was a very little bit of light rain during the race, but we had forecasted that there was going to be slightly heavier than that. Not enough to go to inters but enough to be very difficult on dry tyres.
"The medium may well have provided slightly more coverage in those conditions being a slightly softer compound, and that's why we erred towards that slightly softer, medium tyre."
Mercedes had been able to undo the same error on Bottas after the Finn collided with Verstappen after his pit stop. Contact forced Bottas into the wall, damaging his tyres -- he pitted a lap later to swap the damaged mediums for the hard tyre.
Vowles also revealed that a mistake at the end of Hamilton's stop delayed Bottas' exit, as Mercedes had been forced to pit its drivers at the same time.
"When you come in for a double-stack safety car [stop], what's really important is making a gap between your cars, so that the first car can be serviced in the pit lane and the second one can slot straight in. And Valtteri did that perfectly on track.
"Lewis had his pit stop, drove out, and you would've seen Valtteri came straight back in again. And now it's a straight race between Vettel, Verstappen and Valtteri for a pit stop.
"Unfortunately, as Lewis left, he clipped one of the [wheel] guns and it took just a few seconds for them to reset properly and the cost to us was a couple of tenths. That's it, but that's all you need."