In the interest of keeping costs down and streamlining development in the COVID-19 era, 2021's Formula 1 cars will carry over a great deal from their predecessors. On the outside, they’ll look pretty similar to what we saw last year. However, there are a number of small aerodynamics changes, in addition to a new sturdier tire compound and additional financial regulations, that have introduced new challenges for teams over the winter break.

Fortunately, Mercedes’ technical director, James Allison, has unpacked all of these in an the team released today. If you want to understand what’s really going on behind the scenes this year, it’s pretty much essential viewing.

Allison begins by covering the aerodynamics-related changes to the rules, which are small in isolation but, together, take a decent chunk of speed out of the cars, bringing them more in line with 2019 performance. The technical director sheds light on the rule-makers’ decision to slow the cars down aerodynamically:

There was a concern that if we left the aerodynamic development of these cars unchecked, then the performance would just keep increasing — it’s been doing it for a number of seasons now — it would keep increasing to a level where the cars would just simply outgrow the tires and perhaps even aspects of the circuits.

So there was a good need to bring the performance down a bit on the car so that they would be able to go into the new season of 2021 with the mechanical packages designed for 2020, remember, and be confident that the performance of the car would be matched to the physical infrastructure that the car was built around.

These measures have taken the form of revisions to the chassis floor right ahead of the rear wheels, carving a triangular cutout that Allison says will add about a second to lap times alone. Rear brake duct winglets were reduced in size, rear diffuser fences have been shortened to not cut so close to the track surface, and vertical slots in the floor near the bargeboards have been nixed, all reducing ground effects.

From there, Allison goes on to cover the new tire compound, which the teams had only opportunities to experiment within Portugal, Bahrain and Abu Dhabi last year. The new composition is “more durable” and “more effective,” but heavier as a consequence, contributing to 2021 cars that will be 6 kilograms heavier than last year’s.

Tires aside, the weight limit has been raised by 3 kilograms, and Allison says the fact Mercedes’ 2020 chassis was under the weight limit has given the team’s engineers a bit of freedom to determine where and how to best invest the additional mass.

One of the significant features of last year’s Silver Arrows that won’t be making it to this year’s iteration is of course the Dual-Axis Steering system, nicknamed DAS. This aspect allowed the driver to reduce the toe of the front tires when traveling down straights by pulling the steering wheel toward them.

If you’d like to read a deeper dive as to how valuable DAS was, check out from the beginning of last season. The crux is that while toe-out is useful for cornering, it introduces inefficiencies elsewhere, ultimately reducing straight-line speed and promoting uneven tire wear. Mercedes was the only constructor that designed a solution to this issue last year, though, after inevitable protests from fellow teams, DAS was deemed illegal for 2021 and onward. In fact, the way the regulation’s been written is an amusing example of F1 rule makers closing any potential loopholes with excruciatingly specific and redundant language. Per :

The re-alignment of the steered wheels must be uniquely defined by driver input to a single steering wheel permitted to have only one degree of freedom, which must be rotational, and the relationship between the angle of each steered wheel to the angle of the steering wheel must be a strictly monotonic function.

The upcoming season will also limit the amount of power unit upgrades teams can make over the course of the season, from the previous three to just one. And as a way of evening the playing field, teams that were more successful last year will be allotted less time in the wind tunnel to refine their designs this year. As 2020 champions, Allison speaks to the challenge that his squad will have to make the most of the time they do get.

Even though we’ll have to wait another year for truly comprehensive, next-generation changes to F1 cars, 2021 makes enough small alterations to hopefully prevent it from being a total rehash of 2020. If the words of Mercedes’ technical director are anything to go by, the slight rule tweaks have still been enough to keep teams on their toes.