Ulrich Fritz’s Mercedes team HRT relies on high-tech from formula racing when it comes to handling the tyres: how this helped them achieve pole at the Sachsenring and what the risks are
After Luca Stolz’s victory at the Sachsenring, challenger Thomas Preining was puzzled as to how the HRT driver was able to bring the tyres into the window so quickly after the stop. And the pole lap of the Mercedes-AMG works driver, who was six tenths faster than his brand colleagues, also baffled the competition.
When a regulation clarification came on the same day that heating the tyres by sunlight in the pits is not allowed, the mystery seemed to be solved for many. But HRT might not have used the sun at all at the Sachsenring. Instead, four squares on the cockpit display of Stolz’s HRT-Mercedes give a hint to a complex tyre analysis system.
A secret weapon of the team led by ex-Mercedes DTM director Ulrich Fritz? “It’s nice to have some fancy flashing lights in the cockpit that might help the driver a little bit, but that’s the fourth of five steps” that there’s something bigger behind it. “Because the flashing lights don’t do you any good if you make the wrong decisions. “
HRT team boss on Pride pole: “That was the key “
In fact, since the winter of 2021, HRT has been working with French tyre analysis service provider FORS, which also supports three Formula One teams, to better understand the tyres. According to Fritz, the strong Sachsenring weekend, where Stolz was by far the best Mercedes-AMG driver, was a result of the collaboration.
“We said in the morning before qualifying: now it’s time to drive strictly according to data!” reveals Fritz. “That was the key.” Because the simulation had spat out that the right way was to drive only a preplap after the outlap to prepare the tyres before the decisive attempt follows.
“We actually expected the others to do the same,” the HRT team boss wondered why the other two Mercedes-AMG teams did an additional preparation lap – and thus could no longer make the most of the tyre’s “peak”.
Prema tyre advantage in Formula racing convinced Ulrich Fritz
But how does HRT benefit from its work with FORS and why does it only now seem to be really bearing fruit? “We started working intensively with virtual tyre models about two years ago – and it’s a long-term strategy,” explains Fritz, who knew tyre specialist Frederic Ruat’s French service provider from his time as HWA boss in Formula E and from the junior formula series.
“The Prema team got more out of the tyres in Formula 2 and Formula 3,” Fritz recalls of the Italian HWA competition, with which Mick Schumacher, among others, became champion in 2020. “That made it clear that they were doing something special. And when I then started in GT, I was surprised that hardly any teams went into such detail. “
DTM’s switch to Pirelli tyres a setback
So HRT teamed up with Prema partner FORS. What followed was hard building work. “We know how important it is to get valuable data first before the results come. But when we finally had the data from the Michelin tyres, the switch to Pirelli came. That was a setback – and we effectively started from scratch again.”
How is such a virtual tyre model created? FORS first analyses the tyre at rest, then uses a special trailer on a race track with the Pirelli wheel positioned in the middle. This allows the effects of vertical forces and lateral forces to be measured in isolation. The contact area of the tyre is also precisely tested. Based on this, a virtual tyre model is created.
Whether this correlates with reality will be checked during private tests of the HRT team with the Mercedes-AMG GT3. This is because not all the necessary sensors are allowed at the DTM weekends. Before the test work then begins for the actual race weekend, the software runs hot to perform simulations. “80 per cent of the work takes place before the weekend,” confirms HRT technical director Laurent Fedacou, who previously worked with FORS at the Formula E team Venturi.
“At the weekend, we just repeat the simulations with the current temperatures,” says the Frenchman. “If we do a simulation at home with 25 degrees track temperature and we see on the weekend that it’s only 20 degrees, then we can adapt the warm-up process and the tools to give the right information to the driver.”
That’s also why simulations are done right up until the last moment before qualifying, to get the most representative data possible. How to brief the drivers before the session then? “First we decide how many prep and push laps to do,” explains Fedacou.
“Then, based on the temperature outside, we define how we warm up the tyre. We tell the rider: ‘We need five longitudinal braking manoeuvres, zigzag twice, watch the balance from left to right, because the Sachsenring has a lot more left turns than right turns. “
“The aim is for all four wheels to be at 100 per cent and the box to be green,” said the technical chief. “Then they are in the window and the driver can start doing push laps.”
That all this is a tightrope walk was revealed by the two qualifying sessions at the Sachsenring. “In the first qualifying Luca warmed up the tyre perfectly – and our specifications of how much energy he had to put into the tyre were spot on,” he points to the temperature of the carcass and the tread, the air pressure and the vehicle balance. “That’s how we managed to get this pole. “
What risk the HRT approach poses
In Sunday’s qualifying, however, when Stolz was third, 0.179 seconds behind Mirko Bortolotti, “not all the parameters were exactly right anymore,” he admits. “Luca had some pick-up on the way out of the pits and had to make sure the tyre was clean. As a result, we were a bit out of the optimum window.”
In general, pushing the limit through simulation also carries risks, Fritz says. “If you’re off on just one parameter, you’re gone. But the beauty is that we have a systematic, data-driven approach instead of relying on gut feeling. It’s repeatable. And if you don’t make it, at least you know what went wrong. That’s better than the rider coming back and saying the feeling just didn’t fit.”
This is despite the team saying it has invested a six-figure sum in working with FORS to understand the tyres. “We never use 15 sets of tyres for that in testing,” he says, comparing his team to the competition – and also seeing potential to save costs with the systematic approach.
This is how the system works on the cockpit display
And then there’s the system in the cockpit that shows the driver on the display whether the tyres are in the right temperature window. “The four squares are the four wheels,” Fedacou explains. The number in the box is a percentage from 0 to 100. If the tyre is still too cool, the box is blue; if the temperature is too high, it is yellow or red.
“The goal is for all four wheels to be at 100 per cent and for the box to be green,” said the technical director. “Then they are in the window and the driver can start doing push laps.”
That all this is a tightrope walk was revealed by the two qualifying sessions at the Sachsenring. “In the first qualifying Luca warmed up the tyre perfectly – and our specifications of how much energy he had to put into the tyre were spot on,” he points to the temperature of the carcass and the tread, the air pressure and the vehicle balance. “That’s how we managed to get this pole. “
What risk the HRT approach poses
In Sunday’s qualifying, however, when Stolz was third, 0.179 seconds behind Mirko Bortolotti, “not all the parameters were exactly right anymore,” he admits. “Luca had some pick-up on the way out of the pits and had to make sure the tyre was clean. As a result, we were a bit out of the optimum window.”
In general, pushing the limit through simulation also carries risks, Fritz says. “If you’re off on just one parameter, you’re gone. But the beauty is that we have a systematic, data-driven approach instead of relying on gut feeling. It’s repeatable. And if you don’t make it, at least you know what went wrong. That’s better than the rider coming back and saying the feeling just didn’t fit.”
This is despite the team saying it has invested a six-figure sum in working with FORS to understand the tyres. “We never use 15 sets of tyres for that in testing,” he says, comparing his team to the competition – and also seeing potential to save costs with the systematic approach.
