Why Losail’s “standard” kerbs have caused unexpected tyre problems for F1

Concern over potential tyre failures prompted Formula 1 to change its track limits rules ahead of qualifying for its sprint race at Losail International Circuit today.

Further changes are under consideration for tomorrow’s grand prix including a maximum stint length or minimum number of pit stops.

The problem came to light after the tyres used in yesterday’s sole practice session were analysed by Pirelli. They suspect damage inflicted by the kerbs around the refurbished track led to the problem.

“We saw an indication that there was, in the construction of the tyre on the sidewall, a small separation between the carcass core and the topping compound,” Pirelli’s head of motorsport Mario Isola explained.

“Obviously then we went deeper into the analysis and [found] this is due to strong impact against or repeated impact against something. We believe that it is an impact against a kerb.”

Kerbs caused tyre problems on F1’s sole previous visit to Losail in 2021. Since then the track has been refurbished and new kerbs installed but Isola says the problem has remained.

The previous kerb design had two raised rows, one higher than the other. The latest design only has a single row where the kerbs reach a point three to five centimetres above the track surface.

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“The geometry of the kerbs we have here is similar to the geometry of the kerbs that we had in 2021, the second row of the kerbs,” Isola explained. “And in 2021 we had a similar issue.”

Another contributing factor is that drivers can gain lap time by running along the kerbs at some points on the circuit, such as turns 12 and 13.

“It’s not just the geometry of the kerb, because these kerbs are used in many other circuits,” said Isola. “It is the time and the speed they stay on the kerbs that is important.

“So here, during the lap, all the drivers are spending quite a lot of time at the high speed on the kerbs and this is damaging the construction.”

The effect of drivers running along the high kerbs was “like you take a hammer with a pyramid at the top and you [strike] against the sidewall 110 [times] per second,” said Isola.

The change in the construction of the kerbs means drivers no longer feel a smaller set of bumps before reaching the taller bumps.

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“In 2021 this was the second row [of kerbs], so when they were going out, the first row was 25 millimetres and the second row was 50 millimetres. Now we have only one row that is 50 millimetres.

“So they jump over the kerb and they go down and that’s probably why we found out this issue in free practice. Luckily we found out this issue in free practice and I believe it’s a good example of predicting an issue and also working with the other stakeholders in order to avoid any safety issue during the race.”

The kerbs are widely used at other tracks. “This is quite a standard kerb,” said Isola. “Here the difference is the amount and the speed.

“Obviously there is no obligation to consult us. If we are consulted that we are happy to give our feedback. The point is that this track is new, the kerbs have been positioned just one month ago so it was also impossible to make any inspection or any check earlier in the year.”

The tyres would be at risk of failing if drivers continued to run along the kerbs for many laps, said Isola. “If you continue to run on the same tyre then a small fracture can continue, and then you can reach a point where you have a loss of pressure. And if you have a loss of pressure, obviously you run flat.”

When F1 previously raced at Losail the series used 13-inch wheels and the tyres had taller, more flexible sidewalls. However Isola said the new generation of tyres for 18-inch wheels were not necessarily less able to withstand the damage meted out by the kerbs.

“The smaller sidewall for sure is not helping this effect because you have less opportunity to absorb the hit. But in general, when we made some specific test on the 18-inch tyre we realised that the level of resistance of the construction was in line with the 13-inches. So we are not saying that the 18-inch tyre is weaker compared to the previous tyre.”

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Although teams conducted simulations of the revised Losail circuit, Pirelli said this gave no indication of the potential problem with the kerbs. The damage sustained by the tyres was minor and only picked up once Pirelli cut apart the tyres used in practice and examined them with a microscope.

“If I cut the tyre and I show you the section, you cannot see any damage,” said Isola. “It’s so small that we can [only] find the damage with a microscope.

“So it’s not an issue that I’m here saying ‘guys, pay attention because we have a big issue’. No, it’s an indication, but obviously we cannot ignore it.”

Pirelli are entirely confident the tyres will last for the 19-lap sprint race “because of the tyres we analysed yesterday,” said Isola. They will examine the tyres used in tonight’s race before a decision is taken on whether further restrictions need to be put in place for the race.

“After the sprint [race] all the drivers will return the set of tyres used. We are going to cut the tyres again, analyse the tyre, find the result of the investigation and inform the FIA.

“If the problem is still there the solution for tomorrow is to impose a maximum number of laps for each set of tyre.”

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A requirement for all drivers to make at least three pit stops is also being considered. Isola said this is necessary to introduce variety into strategies.

“It’s 57 laps and if you impose two [pit stops], the risk is to have all the cars on the same lap coming in. That makes confusion. So if you impose a minimum number of laps at 20, but three stops, you have the flexibility to play around this.”

Although Isola said Pirelli were not consulted on the changes made to Losail before the teams arrived there, he believes no one should be blamed for the problem.

“I don’t want to talk about ‘fault’,” he said. “There is an issue and we have to work together to fix the issue. Then obviously you learn from issues and for the future, we need to find a better process in order to anticipate it.

“But it’s important that if there is an issue that is not predicted, we have a system that is happening before we have any tyre issue on track and we can fix it, even if we have to change the schedule or the track limits or whatever.”

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