SAKHIR, Bahrain -- Pierre Gasly set the fastest time on the first day of this week's preseason test in Bahrain, but it was Mercedes who turned heads with a significant upgrade to its car.
Gasly used the softest compound tyre to set the fastest time of the day in his AlphaTauri, putting him 0.457s clear of his nearest rival. The time had all the hallmarks of a low-fuel effort, having been set on a single-lap run, on the C5 tyre compound, and once the sun had gone down and track conditions were at their best.
The gap to Carlos Sainz in second place looked impressive on paper but is easily put in context by the Ferrari running a tyre compound two steps harder. The softer the compound the more grip the tyre offers when new but the quicker that performance drops away. The performance gaps between compounds are expected to be worth 0.5s in normal conditions.
Charles Leclerc, who drove the Ferrari in the morning before handing over to Sainz at lunch, set the third fastest time, 0.172s off his teammate using the same C3 tyre compound. Lance Stroll was fourth fastest, a further 0.2s adrift and using the C5 compound, ahead of Alex Albon in the Williams on the C4s. The session ended a few minutes early when Sergio Perez, who was 10th fastest in the Red Bull on C3s, spun at slow speed and beached his car in the gravel on the exit of Turn 8.
But the lap times alone without the context of fuel loads and engine settings can be misleading, and instead the focus within the paddock was on the new look of the Mercedes. The car featured a significant and obvious upgrade to its sidepods in Bahrain, with smaller outlets and a complete separation between the side-impact crash structure and the sidepod itself.
The design immediately raised questions about its legality, but Mercedes is confident its dialogue with the FIA during the car's development means the governing body would rule in its favour if the design is protested.
However, the early indications are that Mercedes still has plenty of work to do to extract performance from its car. The W13 continued to struggle with porpoising - a problem that impacted all teams to some extent at the first test in Barcelona (link to story) - and both Lewis Hamilton and George Russell seemed to struggle with the car under braking.
"The car, we are really proud of what we have achieved in terms of concept, but now we need to make it go fast," team boss Toto Wolff said. "It's a development direction that we like. It's about tuning the car. We're experimenting a lot and approaching it with curiosity.
"There are issues that are Bahrain specific; it is hot, the cars are bouncing on the straights and through the corners, so it's a tuning question and we haven't really looked at the performance data, yet."
Hamilton, who drove in the morning, finished the day with the 11th fastest time, while teammate Russell, who took over in the afternoon, finished ninth fastest. Both drivers set their fastest laps on the C3 tyre compound.
The Haas F1 team missed the morning session as a knock-on result of its freight getting delayed on its way to Bahrain. The team managed to get its car out on track for the afternoon session for 47 laps with reserve driver Pietro Fittipaldi at the wheel.
Haas is expected to get the four hours of running it missed on Thursday morning back later in the week because the freight delay was a result of a Formula One charter suffering technical issues. The current plan is for Haas to run two hours longer into the night on the second and third days of the test to make up the time, but exact details have not yet been confirmed.
Final times, day one:
1. Pierre Gasly - AlphaTauri - 1:33.902 - 103 laps
2. Carlos Sainz - Ferrari - 1:34.359 - 82 laps
3. Charles Leclerc - Ferrari - 1:34.531 - 64 laps
4. Lance Stroll - Aston Martin - 1:34.736 - 50 laps
5. Alex Albon - Williams - 1:35.070 - 104 laps
6. Lando Norris - McLaren - 1:35.356 - 50 laps
7. Valtteri Bottas - Alfa Romeo - 1:35.495 - 66 laps
8. Sebastian Vettel - Aston Martin - 1:35.706 - 39 laps
9. George Russell - Mercedes - 1:35.941 - 60 laps
10. Sergio Perez - Red Bull - 1:35.977 - 138 laps
11. Lewis Hamilton - Mercedes - 1:36.365 - 62 laps
12. Fernando Alonso - Alpine - 1:36.745 - 24 laps
13. Esteban Ocon - Alpine - 1:36.768 - 42 laps
14. Guanyu Zhou - Alfa Romeo - 1:37.164 - 54 laps
15. Pietro Fittipaldi - Haas - 1:37.422 - 47 laps