Today marks the first day of the second pre-season test for Formula One, and as expected, teams have started introducing radical design changes based on data gathered from the previous test. One of the biggest changes came from the Mercedes team, which introduced a wacky new sidepod design on its W13.

This post is a guest post from Kate Lizotte, co-founder of . You can find her on .

Let’s break it down. This year, regulations allow for vents to be carved into the sidepods to allow for better airflow to both cool the power unit and channel air away from the competitors following in that car’s wake. It’s all part of F1's bid to make for closer racing.

But Mercedes has taken it a step further. Where most other teams have continued down the traditional route of keeping the sidepod and side impact structure — the parts of the car that protect the driver in the event of a T-bone crash — as a single, cohesive unit, Mercedes has separated them.

Regulations dictate where the side-impact structures (SIS) need to be, but the rest is vague, and those SIS don’t actually have to really work because F1 doesn’t mandate side-impact tests anymore. The expectation was that teams would continue down the conventional path — but this is racing, and when there’s no rule specifically disallowing a design feature, then it’s pretty much fair game.

To help contextualize this change, let’s run through some history. Back in 2014, F1 mandated that each car needed to have two SIS on each side of the car. It started as a way to reign in the wild sidepod design shapes that were springing up, thus reducing costs and throwing a bone to the backmarker teams that couldn’t afford that.

Now, though, the regulations only state that the SIS be placed 50 mm higher than it was in the past — a crucial change, since most teams followed Ferrari’s 2017 example by placing the upper SIS low and ahead of the air inlet. Raising the upper SIS messes with the aerodynamic flow of air around the sidepods, so teams have had to completely rethink their design strategy.

No one has done what Mercedes has done, though. Here’s a little more on the exact changes, via :

Decoupling the upper SIS from the sidepod bodywork has then allowed the team to think laterally about the size, shape and orientation of the internal components, the inlet plus the bodywork that shrink wraps tightly to them.

The sidepod itself is also pushed back from the SIS when viewed from the side, allowing the team some space to include some downwashing chassis canards ahead of the inlet (red arrows). This has been spun 90 degrees, with a tall, slender opening allowing it to minimise the width of the sidepod.

Those SIS changes have radically changed the rest of the W13's design, which has resulted in a wider body from the halo back to help more accurately channel airflow and provide better cooling. And there’s nothing in the regulations to say Mercedes can’t do any of this.

To help illustrate what I’m talking about, here’s a side view of the new W13, which is absolutely cut:

And here’s the Haas, which looks like it has had an obscene amount of pasta every night since COVID began:

Perhaps the most delicious part of this saga is the fact that Christian Horner, Red Bull Racing team principal, has that Mercedes’ changes go against the “spirit of the regulations” — a truly rich sentiment for a team that has a history of working well within the undefined sections of F1's rulebook. (Red Bull, for its own part, has vehemently denied that Horner has chatted with any media.)

Unfortunately, it doesn’t appear that these changes have done much to help combat the porpoising that has been taking place for these new cars during testing. As they pick up speed, cars appear to be hopping or bouncing as a result of wonky airflow — and which make for a much more difficult car to drive. From the limited coverage we’ve seen of testing today, that issue still seems to be causing the Mercedes team trouble.