As expected, the high altitude in Mexico caused for headaches for both engineers and drivers during the first day of practice around the Hermanos Rodriguez race track. The thin air affected both downforce and mechanical grip, forcing drivers and engineers to find alternative ways to regain the cars’ balance.
Straight-line advantage – After Lewis Hamilton topped the opening practice session with a time of 1m17.327 on the red-banded soft compound, Sebastian Vettel took over the lead in the afternoon session by setting a lap time of 1m16.607 on the same compound. Ferrari was expected to deliver a high level of performance around the Mexico City track due to its characteristics, but the pace of Mercedes and Red Bull suggested that there are three contenders for victory this weekend.
As seen throughout the whole season, Ferrari gained most of its advantage on the straight during the Friday practice session, but the good mechanical grip of the RB15 meant that, in the slow-speed turns, Max Verstappen was significantly faster than his rivals. In the few high-speed corners of the Hermanos Rodriguez track, Mercedes had the upper-hand demonstrating the superiority of its aerodynamics package. In the medium-speed bends, both Mercedes and Red Bull were quicker than Ferrari’s aerodynamically efficient SF90.
High degradation – Although the sport’s sole tyre manufacturer Pirelli supplied a tyre selection that was harder than last year, Ferrari driver Sebastian Vettel’s fastest FP2 lap on the soft C4 compound was slightly quicker than last year’s equivalent. Up to now, the performance difference between the medium and the soft is around 0.9 seconds, with 0.6 seconds between the medium and the hard compound.
Drivers experienced a high level of degradation and graining during the sessions. However, Pirelli’s head of car racing Mario Isola indicated that it was “no real surprise given the cool and damp conditions combined with the lack of aerodynamic grip, which meant that the cars were sliding more than usual. Despite this, the actual lap times were comparable to last year – and with a harder tyre selection. There’s clearly some degradation on the soft at the moment in particular, but a lot will depend on the eventual weather conditions for race day.”
The overnight rain meant that the track was damp and slippery at the beginning of the first free practice session. Most of the drivers had a first taste on the green-banded intermediate tyres early in the session before switching to the slick tyres. In the remainder of that session and in the afternoon practice, Pirelli’s engineers could collect data on all three dry-weather tyres, giving them plenty of information to work with for Saturday and Sunday.
New gearboxes – Five drivers started the Mexican Grand Prix weekend with a fresh gearbox. Valtteri Bottas and Lance Stroll used their previous gearbox for six consecutive events which allowed a penalty-free change for this weekend. Max Verstappen also received a fresh unit after he failed to finish the previous meeting at Suzuka. Following their separate crashes during the qualifying session for the Japanese Grand Prix, both Robert Kubica and Kevin Magnussen used a spare gearbox which permitted the installation of a fresh unit without triggering a grid-drop penalty.
The Toro Rosso outfit decided to request a permission from the FIA to change the cross shaft cover seal assembly on the gearbox of the cars of both their drivers. This was done in accordance with Article 9.5.2 of the 2019 FIA Formula One Technical Regulations.
Fresh engine components – Sergio Perez received a fresh energy store and a new control electronics for this weekend. The Sporting Regulations permit two units of both these power unit components for each driver for the entire stretch of the 2019 season. As the Mexican has used only one unit of both the control electronics and the energy store so far this season, the change does not trigger any penalty.