Mercedes has revealed that Valtteri Bottas' struggle for pace in the opening stint of the Bahrain Grand Prix was caused by a "perfect storm" of problems on the grid.
Bottas led away from pole position, the first of his Formula One career, but was unable to shake the attention of Sebastian Vettel and the train of cars made up of teammate Lewis Hamilton and the Red Bulls behind. Team boss Toto Wolff says Bottas' poor pace at the start was due to incorrect tyre pressures, caused by a broken generator on the grid,which then left Mercedes unable to react to Sebastian Vettel's race-defining pit stop on lap 10.
"We had the perfect storm at the beginning our generator broke on the grid and we couldn't bleed Valtteri's tyres, so it was the wrong tyre pressure on this car," Wolff said. "I knew that he would be struggling, and Sebastian running second there was nothing we could've done. That opened up the opportunity for them to undercut us and they did it quite early and that made them win the race."
Mercedes also suffered during the pit stops, with a loss of power in the garage preventing the team from using its wheel guns properly. Wolff thinks the problems masked the true pace of the world champions, who had locked out the front row of the grid by 0.4s on Saturday.
"Valtteri's problem was pretty clear, he was struggling in the first stint and that was clear, and afterwards you just need to have the tyres in the right window and obviously with Valtteri's car we weren't able to have that. At times he was very quick and at times he lacked the pace.
"With Lewis we never saw it actually. Him running third, what could've been or what his pace would have been we don't know. He said at a certain stage that it wasn't about his pace in the car and then he was catching up in a brilliant way but we haven't seen the real pace."
Bottas, who finished third, behind Hamilton said the tyre pressure problem made the start difficult, though he is yet to understand why he struggled so dramatically in his second and final stints.
"I felt like I was driving on marbles all the time, but for the other two stints there's not yet an explanation for why the rear end wasn't working and I had a slow pace. The slow pace was due to rear end problems, but we haven't yet answers for why that happened.
"For me it was not normal that it was oversteering so much, I used all the tools I had -- diff, brake bias -- to try to cure it, trying to save the rear tyres, but there was no way. The tyres were OK for the first couple of laps but very quickly, when the temperatures went up, it became very tricky. It was quite strange to lose so much pace, but it's not so easy to explain why, yet."