Germany’s Auto Motor und Sport today published an interesting article outlining a very real problem teams have with the current aerodynamic rules first instigated in 2017.

Entitled Der Fluch der breiten Reifen translated to The curse of wide tyres, it reveals some of the specific problems teams have faced when dealing with the wide tyres and the wider bodied cars we see today. Even more interesting is the extent to which Ferrari was hampered when trying to develop their car during the 2018 season, resulting in a serious performance dent mid-season.

Further, seven out of ten teams had to take at least one step back in their aerodynamic development during the season, including Ferrari and it was this major setback may have cost them the title, even when considering Vettel’s driver errors.

The problems faced by most of the teams were mainly around correlating simulation to real-world physics, and only those with the biggest purse strings were able to work around this, hampering competition from the midfield and denying the back-markers a chance to move up the field.

In what was an FIA / FOM move to improve the cars, after misjudging what fans were demanding from their sport; resulted in a return to faster cars in a misguided bid for breaking lap records. So we saw wider, heavier more impressive looking cars, wider tyres, and more aero pieces. A huge error.

Below is a direct translation from the Auto Motor und Sport piece, so please forgive and grammatical errors.

The curse of wide tyres

The problems faced by those affected by the aero correlation issues had a similar problem in different phases of the season, namely unstable downforce at the rear.

In order to keep the tyres good during the race, almost all of them temporarily had more angle on their wings. This was at the expense of the top speed. The reason why? Often the devil was in the detail. Many had simply gone one step too far with the floor, the baffles or the wings in the development and was forced to eventually go one step back again.

Ferrari and Red Bull in the Aero Trap

Ferrari fell into a hole after the summer break or to be precise, from the Singapore GP. At the high-speed races in Spa and Monza there was a car with a special aero package at the start. With the exception of the front wing, which made its debut in Sochi, all the aerodynamic developments at Ferrari were in vain.

The rear wing, the underbody, the baffles. Everything a step backwards. It took three races until Ferrari realised that something was wrong with the correlation between wind tunnel, CFD simulation and race track.

“We had to find out where and why we took the wrong turn,” reveals Sebastian Vettel.

In order to track down the problem, Ferrari tried out a new idea on the underbody four times in a row. There were even more slots in the bottom plate between the wheels.

Vertical fins were also used to channel the air flow. All tests on Friday morning showed that the contact pressure was not as stable as with the old floor. As soon as Ferrari returned to using the floor before the summer break, the car behaved normally again. So Kimi Raikkonen won the GP USA.

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Red Bull also went a step too far in the search for more downforce and less drag.

Between the GP England and the GP Italy, Max Verstappen and Daniel Ricciardo could not even get on the podium under their own power.

In the rainy Budapest qualifying Red Bull experienced a nasty surprise. In the conditions they had been waiting for all year, the drivers only finished 7th and 12th on the grid.

In the analysis, the engineers found that the diffuser did not do what it was supposed to do under certain conditions: deliver constant downforce. The aerodynamic engineers made corrections and also reduced the car’s rake.

Not dramatic, but big enough to turn third in the team performance pecking order, but at least back to a candidate for victory in the last seven races. Red Bull still ended up in midfield on the straights however.

Renault, Toro Rosso & McLaren: The car only works for one type of corner

Renault last year had solved the problem of car instability in corners with long radii with a diffuser modification.

With the new 2018 car, the same phenomenon occurred again. Understeer at corner entry, oversteer at apex, limited confidence of drivers in their car.

This time, however, whatever Renault did, didn’t help the dilemma. The wind tunnel attested the underbody, which debuted in Spa, clearly better values. But they did not arrive on the track. Only when the new floor was modified with a few old elements and ideas did a slight improvement occur.

With McLaren it was the other way around. Working properly in fast curves, but the problem was in slow ones.

“Unfortunately, there are fewer and fewer fast corners,” regrets Operations Manager Andrea Stella.

“With more downforce, more and more curves go full throttle for everyone without any problems.”

Toro Rosso was faced with exactly the same riddle. Only four races before the end the technicians got it under control with an extensive aero update. Front wing, underbody and side box wings were new.

McLaren had already taken a wrong turn with their concept before the season. Just like Williams did. The design office around technical director Paddy Lowe spent half a year doing a doctorate on a failed front wing, until finally progress was made.

But the backlog was already much too big to save anything from the messed up season.

Development driver Robert Kubica explains the dilemma: “We still had correlation problems with the simulator at the beginning of the season. These discrepancies between the tools and reality ultimately led to the misjudgment of the car.

“We really thought we had a good car. The simulator is fed with data from other departments. And they were wrong.” he concludes.

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Simulation tools are at their limit

Force India realised after two races that the rear side box retraction was causing instability at the corner entrance.

The downforce fluctuated too much. It was a few centimetres more or less radius, a few degrees more or less inclination compared to the ground.

Peanuts from a layman’s point of view. Dramatic from the point of view of the drivers, who always lose confidence when the car out of the blue loses its contact pressure or shifts it from the front to the rear or vice versa.

Technical director Andy Green explains:

“Our problems were due to the poor correlation between the wind tunnel, CFD and the real car. One of our development tools sent us in one direction, but suddenly another tool spoke against it.

“And that was confirmed on the track. It wasn’t easy to solve this riddle. Our experts in this field told me that we understood the error and how it could have happened. But you can’t be sure that something like that won’t happen again.

“But we shouldn’t run into the same trap again so easily. We now know that we will have to work a little more thoroughly in this area in the future.”

The problem with correlation is surprising. How can something get out of hand that apparently still worked in 2017?

And the rules had changed only marginally. “If you keep moving a car forward and climb up the development curve, you will eventually reach the limits of simulation technology.

“Every detail is defined more and more finely and pushed to the top. Correlations can easily go wrong, which can cause the whole house of cards to collapse. The higher you build the house of cards, the easier it collapses,” Green concludes.

This is not an unusual phenomenon in Formula 1. Engineers used to be desperate about their simulation tools overnight when they tried to push the limits of a regulation.

“In a new regulation, the fruit is still hanging far below the tree so to speak,” explains Green.

“It’s relatively easy to reap the rewards of large performance steps. But with time it gets more difficult. The development tools have to work more and more precisely.”

Wider tyres, larger air vortices

McLaren engineers Simon Roberts and Andrea Stella attribute the problems that many teams have run into this year to the wider tyres and the larger underbodies.

Wider tyres also mean more turbulence. And larger underfloors contribute more to overall downforce than smaller ones. Green agrees with the McLaren theory:

“Modeling the turbulence behind the wheels is the most difficult task for us in formula cars. The deflection of the airflow on a straight line is extremely different from the turbulence produced by the wheels in the middle of the bend.

“The key to the performance of the entire car lies in the right simulation. This is all much easier for vehicles with fairing wheels.

You wouldn’t believe how much work we put into this. And the wider the tyre, the worse it gets”.

The bigger the teams, the better the tools. Nevertheless, teams like Ferrari and Red Bull are not safe from going astray.

“The tools help us, but they require a lot of programming resources,” says Green.

“And the technology is not yet fully developed. For example, we try to simulate the turbulence in a certain area behind the wheel. It may happen that the calculations are right for that area, but not for the one behind or before it.”

The more the engineers work with aerodynamic aids that specifically generate vortices to repel others or to seal off aerodynamically sensitive areas (the aero devices you see all over the current cars), the greater the danger of getting into the wrong direction with this network of baffles.

Everything revolves around averting the damaging turbulence caused by the inner edge of the front wing and the front wheels, or between the base plate and the rear tyres.

Nico Hülkenberg believes that this is exactly where the huge lead of the top teams comes from:

“They have understood something we haven’t understood yet. We have to decipher this secret. We won’t be able to do that with continuous development alone.”