BAKU, Azerbaijan -- Mercedes boss Toto Wolff believes two key factors helped his drivers achieve a surprise result and beat Ferrari's Sebastian Vettel to the front row of the grid at the Azerbaijan Grand Prix.
Prior to Saturday's qualifying, Ferrari had dominated all three practice sessions and appeared to have a pace advantage on the straights and in the corners at the Baku City Circuit. However, the Italian team's chances were slashed when Charles Leclerc crashed into the barriers in Q2 and then faded completely when Sebastian Vettel was 0.3s slower than the two Mercedes in Q3.
Wolff believes his team's advantage was partly down to the slipstream the Mercedes drivers were able to get on Baku's 2km back straight and partly down to the way the car managed its tyres. However, ensuring it was in a position to capitalise on both required some unusual tactics as the cars left the pits for their final qualifying lap.
In qualifying, teams often try to gain an advantage by being the last car to leave the garage. Track conditions are usually better at the end of the session and it allows drivers to benefit from any potential slipstream. There are dangers, such as leaving it too late and running out of time, but on the whole it is usually considered an advantage to be last on track.
At recent races, Mercedes had observed its rivals -- in particular Ferrari -- had waited for the Mercedes cars to leave the garage before sending its cars out. But unwilling to play a game of chicken as the session clock counted down, Mercedes opted to send its cars out first but then instruct them to pull over in the area designated for practice starts at the end of the pit lane. The dummy played out perfectly, seeing Vettel -- and a gaggle of other cars -- leave their garages after the Mercedes but join the track ahead of them, culminating in Valtteri Bottas and Lewis Hamilton benefitting from the best slipstreams at the back of the pack.
"You always need to evaluate between trying to get a bit of a tow effect and compromising your out-lap," Wolff said after the session. "You can see how wrong it can go in Shanghai for some of the cars that weren't able to cross the line.
"In each of the qualifyings we saw a little bit of a pattern, that everybody waited for us to go out, and this time we thought we've got to try something else, and this is what we did. We decided it this morning."
But it wasn't just the tow that Mercedes benefited from; the car was also quick in the tight middle sector compared to Vettel, which is where tyre temperatures are crucial. Ironically, Leclerc's crash had extended the session to allow for barrier repairs and saw Q3 start at 18:45 local time. The delay meant the sun was signifcantly lower in the sky and the temperatures plummeted, playing into the hands of Mercedes.
"I think we gained relative performance with the dropping temperatures," Wolff added. "I think that probably with the track and ambient of this morning they were in a league of their own, and once it got cooler, probably the competitive order changed.
"But when you see this kind of gap, it's never the car has suddenly lost performance, because you know there is performance, it's just that you're not having the tyre in the right operating window. The longer the session went, the more we got it there, and towards the end, from a car that was not making the drivers happy in the morning, we ended up with a car in Q3 that was good."
By the end of Q3, Mercedes not only had better track position than the sole remaining Ferrari, it also had its tyres in the perfect operating window.
"I think it was a double whammy," Wolff added. "He [Vettel] was out by himself with no tow and the ambient temperatures and track temperatures came towards us at the end. Our car got better the colder it went."