TECH TUESDAY: What exactly are the revised 2021 aero regs – and will they shake up the order?

Technical Contributors

Mark Hughes and Giorgio Piola
V1 Germany F1 Tech

With Formula 1's radical rules overhaul having been pushed back to 2022, the 10 teams will be required to run their current cars next season as well – though they won't be exactly the same. The FIA recently announced further measures to trim downforce off the cars for 2021, in addition to those already confirmed earlier in the year. In this week's Tech Tuesday, Mark Hughes explains exactly what those measures will mean for the cars, with technical drawings from Giorgio Piola.

What exactly do the new regs stipulate?

In addition to the reduction in width of the floor from 1800mm back from the front axle, the floor slots have also been removed as part of the FIA's move to reduce downforce for 2021. The downforce generated by the underbody is a function of its plan area and the air pressure difference beneath the floor with that above it.

The diagonal cut to the floor reduces its plan area and the removal of the slots will reduce the pressure differential.

READ MORE: FIA outline downforce changes for 2021


The 2021 rules mandate the removal of the slots circled and a diagonal cut to the floor

The longitudinal slots are used to create vortices at the underfloor’s edges to act as a virtual skirt, sealing off the floor and preventing the airflow escaping and having untreated airflow being sucked into the underfloor.

The lateral slats ahead of the rear tyres are more about creating a better pressure regime for the flow around the diffuser otherwise disturbed by the rotating rear tyres.

In addition to the floor changes, the winglets on the rear brake ducts, which create downforce that is fed directly to the wheels and is therefore very efficient, have been limited to 40mm (as seen on the lower part of the drawing beneath the red dotted line, in contrast to the current size winglets above the line).


The current winglets on the rear brake ducts can be seen above the red line. The 2021 rules stipulate they must be reduced in size (as seen below the red line)

The final change is to the diffuser fences, which have had 50mm chopped from their lower extremities (as you can see in the image below). They therefore will not seal the diffuser as effectively, further reducing the underfloor’s effectiveness.

Together it is estimated these changes will account for a downforce reduction of around 10% from current levels. It has been done in reaction to the downforce gains already made and those anticipated with development, while the tyres remain the same in specification in the final year of this size of wheel and tyre, before the switch to 18-inch tyres in 2022.


The diffuser fences have had 50mm chopped from their lower extremities, as per the image above

Keeping the rear tyres from being overloaded should allow them to be more raceable and not force Pirelli into specifying very restrictive pressure and camber limits.

Will the revised regs have any impact on the current competitive order?

The changes might conceivably help those teams currently suffering a less efficient aero performance than the best, as the underfloor is by far the most efficient way of creating downforce.

Reducing the efficiency of everyone’s underfloor could result in the best-performing teams losing more, perhaps allowing those behind to close up the gap.

READ MORE: 2021 downforce cut 'more than welcome' as Pirelli prepare for third season with current tyres

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