The Autodromo Hermanos Rodriguez is the highest circuit on the F1 calendar – sitting at 2,200 metres above sea level, over 1,400 metres higher than the next-highest, Interlagos, at 800m. At this altitude, the air is around 25% less dense than is found at sea level, impacting the several critical factors of an F1 car.

Each team’s car is impacted by the lower air density in different ways meaning the order can be mixed up compared to what we might expect as some cars fare better or worse than others. But the racing action remains the same, as each team is equally impacted by these significant changes to the cars’ usual conditions.

Turbocharger

In the modern era, Formula 1 cars are turbocharged, meaning the air is compressed before it’s circulated through the engine, increasing the air pressure within and maximising engine power and efficiency. In Mexico, where the air contains around 25% less oxygen, there is simply less oxygen to burn, so the turbocharger has to spin faster and compress the air more to compensate – working harder than it would at lower altitudes.

While the turbocharger mitigates many of the effects of being at a lower air density on the power unit, it isn’t really possible to work it 25% harder to compensate for the 25% reduction in air as it’s designed to function in ‘normal’ racing conditions. Due to this, the teams do have reduced power unit output over the weekend which in turn impacts the harvesting from the MGU-H – less power means less for the MGU-H to recover and turn into energy.

This lower power unit output can be made up for in performance and speed by the lower drag at the track, meaning we still see some of the fastest top speeds of the calendar in Mexico.

Downforce, Drag & DRS

A Formula 1 car relies on air for downforce so where there is less air, the cars suffer a reduction in downforce given that there are fewer air particles pushing the cars into the ground. Drag is also much lower, as there are fewer air particles for the cars to push out of the way and cut through.

The Autodromo Hermanos Rodriguez has a long main straight (1.2km) and based on track layout alone, the teams would want to opt for a low downforce car setup. But given the lower air density, teams overcome the 25% reduction in downforce by running Monaco specification, high downforce rear wings without the penalty of drag that you’d typically see.

A big rear wing would usually mean a bigger DRS effect, but the altitude means this isn’t the case. DRS works through reducing drag in the car with it active, increasing speed and allowing a bigger chance at an overtake, but if there’s less air, there’s less drag overall to begin with so the effect of reducing this in one car versus another is much smaller. 

Cooling

F1 cars are cooled by air that passes through the intakes and ducts, picking up the heat the components generate before flowing out the back of the car as hot air. At the higher altitude, less air goes through the intakes and ducts meaning the cars are cooled less and components like the power unit or brakes run hotter than they usually would. Simply put, the cooling demand is much greater.

Due to this we see teams opening up their cooling ducts and louvres to bring in as much air as possible before they begin to sacrifice aerodynamic performance. Finding this balance is not only a matter of aerodynamics, but also of performance and reliability for these components.

Brakes 

Braking is one system that is hugely temperature dependent for performance and as such is impacted hugely by the lower air density and reduced cooling in Mexico. Where the brake discs get too hot, a phenomenon known as ‘fade’ occurs where there is not enough friction between the brake disc and pads to slow the car, increasing the car’s stopping distance and braking power. At higher temperatures, brake pads can also become ‘glazed’ as they burn off their surface, making it shiny and reducing friction.

While most teams will choose to overcome this potential problem by increasing the size of their brake ducts, in previous years we’ve seen teams like Ferrari switch to use brake discs with more cooling drill holes to help dissipate the heat without the aerodynamic punishment of increased ducts.

Meeting the demands of running an F1 car at high altitude is a significant challenge for the engineers in the pit lane and back at base for each team but one that they rise to every year to maximise performance in tandem with the drivers on track.

Want to hear more? Check out our newest video summarising these impacts!