Mercedes technical director James Allison has explained the "four significant aerodynamic" differences between the cars that raced last year and those that will take to the track this season.
In a bid to control costs, Formula 1 announced early in 2020 the new aerodynamic regulations would be pushed back by a year to 2002, with the 10 teams obliged to run largely unchanged machinery for the coming campaign.
With aerodynamic loads continuing to increase, placing intense pressure on the Pirelli tyres, changes had to be made to reduce downforce.
"Four quite significant aerodynamic changes were made last year in anticipation of this new season," explained Allison in a video on the Mercedes YouTube account.
"First and foremost, there has been a triangular cut-out to the edges of the floor in front of the rear wheels which when you see it you’ll think 'That doesn't look that big'.
"But on its own, in its rawest form, if you just chop that area off your car it’ll take about a second a lap away from the car.
"Then added to that first change three others came. The first was that the little fins and flicks that were on the rear brake duct were reduced in their span just by a few millimetres but again they were very powerful devices and that change lost a lot of performance from the car.
"At the back of the car underneath in the diffuser area the fences that you can see if you peer up the backend of the car, they were reduced in height so that they can't go as near to the ground, they can't create as good of an aerodynamic seal to the ground as they did previously. Again, they shed a bunch of downforce when they are trimmed upwards.
"Then finally the front-end of the floor as you approach where the bargeboards are if you looked at the 2020 versions of those floors you see that they look a bit like a Venetian blind with lots and lots of slots, an aerodynamic feature there that generates downforce and all of those slots have been removed for 2021."
Acknowledging that to casual viewers the differences may appear minor, Allison said the combination of the four changes will put cars back to performance levels seen two years ago.
He added: "The combination of those four effects, even though if you looked at all of them, you think 'Well, that's not so much. The cars look broadly the same'.
"The combination of those four effects in their rawest form just cut-off and trim back in a way that the rules require brings the performance of the car way back to sort of somewhere near 2019 levels.
"It's been our challenge over the weeks since those rules, the weeks, and months those rules were set in stone to try to recover as much of the performance as possible.
"That has been quite an entertaining ride in the wind tunnel and in CFD to try and make sure that we get that performance as far as possible back onto the car."
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