What is really going on with Miami’s Formula 1 track surface

Such was the determination to get things sorted for this year that Miami F1 chiefs brought in famed track design company Tilke to resurface the Hard Rock Stadium venue.

However, as F1 made its return to the American track, the same complaints returned as drivers bemoaned the unique nature of the surface.

Sergio Perez said that grip had been so low on Friday that it was almost intermediate tyre territory, while a number of drivers really struggled with how dirty things were once they strayed just a few centimetres off-line.

Mercedes driver George Russell said after qualifying that he felt there had been no step forward in the track situation.

“It's been no improvement on last year,” he said. “On-line, it's good grip, but as soon as you put one wheel wide, there's no grip. So overtaking is going to be really challenging.”

F1 tyre supplier Pirelli is perhaps best placed to judge the interaction between track surface and tyres, with its head of F1 Mario Isola explaining what it has found this weekend.

Pirelli conducts detailed analysis of all tracks on the Wednesday ahead of each weekend and its early conclusion was that grip levels on the racing line were not so bad.

“If we talk about the roughness that we measure, we found that the micro roughness is much lower,” he said.

“Last year it was completely different from any other circuit, much, much higher, and the macro roughness increased a little bit.

“So, we were expecting a level of grip similar to last year. The grip was on the low side but more or less in line with the expectation.”

George Russell, Mercedes F1 W14

Photo by: Andy Hone / Motorsport Images

However, the reality of tyre grip is that beyond the estimates of mechanical grip that comes from the nature of the stones used, there is also an adhesive grip that needs to be taken into account.

This relates to how the tyres’ chemicals react to the surface – which on new venues can be bad because the bitumen that is used to lay the asphalt often results in oils coming to the top. These oils do not offer anywhere near the same amount of grip as raw stones.

However, this lack of grip can quickly improve as cars running around the track get rid of this surface layer – which is what happened in Miami as grip ramped up Friday to Saturday.

“The grip increased by roughly 10% and that was expected,” said Isola.

However, the increase in grip caused its own problem because the improvement was only on the racing line – and that meant the contrast between on-line and off-line got bigger.

“The point is that they cleaned the racing line, the grip increased on the racing line, but not outside the racing line,” added Isola.

“So as soon as you were a bit outside the racing line, it becomes snappy, and difficult to control. It's dusty, and the level of grip is not as good.

“I believe that probably is the reason why we saw some mistakes and we saw some drivers struggling in controlling the car.”

Incidents like Charles Leclerc suffered from, where small mistakes that force drivers off the racing line result in bigger moments, were the consequence of this. And it is unclear yet whether the dirty off-line will compromise the chances of overtakes in the race itself.

Water blasting issue

Things could have been improved, Isola reckons, by there being more support events and if the track had been cleaned better ahead of the weekend.

Charles Leclerc, Ferrari SF-23

Photo by: Alexander Trienitz / Motorsport Images

This was something Russell concurred with, as he believed Miami had missed a trick in not making more effort to age the asphalt.

“I don't believe the track was jet blasted like all the other circuits,” said Russell. “Generally speaking, the track designers or whoever do the circuits do a really exceptional job when they relay the tarmac.

“When we go to Melbourne, Jeddah, even Baku, really high grip, lots of grip off-line as well. It creates good racing and good confidence from the driver.

“I think we had a bad experience here last year by being too aggressive with the jet blasting. But now I think it's gone the other way and the result is the same.”

Isola explained that water blasting circuits brings benefits in terms of grip because it removes the top layer of bitumen.

“In the last couple of years, when they decided to resurface circuits, they were using this water blasting treatment with high pressure water,” he said.

“The main mechanism is that this high-pressure water is removing the top layer of the bitumen. So, it's like an artificial accelerated ageing. This exposes the stone in order to have proper mechanical grip, but it didn't happen here. They were the washing the track... and it was too mild.”

Speaking to Autosport on Sunday morning, Miami F1 managing partner Tom Garfinkel explained that the circuit had shied away from full water blasting because of the problems that occurred last year – when it took away too much of the bitumen.

“I think last year might have removed too much off the top and I think that was part of our problem,” he said. “So, we have been doing deep cleaning with brushes. We're not just blowing the track.

“Maybe part of the challenge is we only had one support series, so there is not enough rubber getting down. I jokingly say that I'd love to see the drivers run off-line during practice, lay some rubber down in the secondary line.

Esteban Ocon, Alpine A523

Photo by: Alexander Trienitz

“But it is a green track. You saw from practice to qualifying how the track changed and substantially got a lot quicker, and I think that'll happen today during the race. The track will change a lot from the beginning of the race to the end of the race, but it will be cleaned off and blown. It's just I think it's a lot cleaner than it was last year.”

Like other venues that have been newly resurfaced, it will evolve over time – which should mean by the 2024 Miami Grand Prix it is much more bedded in.