Pirelli: Debris and prolonged tyre usage caused Spa blowouts
F1 NewsThursday, 03 September 2015 at 21:19
An "exceptional combined effect" of track debris and prolonged usage caused Sebastian Vettel and Nico Rosberg's high-speed tyre blowouts at last month's Belgian Grand Prix, Formula 1 supplier Pirelli said on the eve of the Italian Grand Prix weekend.
"The events at Spa can...be put down to external factors, linked with the prolonged use of the tyres on one of the most severe tracks of the championship," they said in a statement at the Italian Grand Prix.
The company proposed, with the governing International Automobile Federation (FIA), a study "to optimise the way in which circuits are cleaned".
The FIA said it was satisfied with the thoroughness of the investigation, and Pirelli's conclusions, and was willing to consider any further safety recommendations.
Drivers said separately that teams had been advised about tyre pressures and cambers for Monza, the fastest circuit on the calendar where cars hit speeds in excess of 360kph.
Rosberg told reporters he was confident he would have a safe car this weekend, but others remained sceptical about the conclusions.
"I don't think anyone is happy with the fact that it's a cut. Seb didn't go off track, there are kerbs and you can use them," Lotus's French driver Romain Grosjean told reporters moments before the statement was issued.
"I don't think it's a good explanation. On the other hand, it's very hard for Pirelli to replicate what we are asking of the tyres when they don't have a current car and some testing to develop their tyres.
"We just need to find a way that the tyres don't go off (wear excessively)".
Pirelli said microscopic analysis on tyres used at Spa found no structural problem. That finding was backed up by further laboratory tests.
The company said 13 748 slick tyres had been used since the start of 2015 without problem.
However, a total of 63 cuts were found in the tread of tyres used over the Spa weekend compared to an average of just 1.2 per event in the previous 15 grands prix.
"All this indicates an anomalous amount of detritus on the track in Spa, with a consequent increased risk of encountering a foreign object," Pirelli said.
Vettel's right rear failure was consistent with a small piece of debris cutting the tyre's structural parts, without penetrating the actual structure, which then failed due to prolonged use.
"Throughout the Spa weekend...cuts caused by debris were found on the tyres of other drivers, which damaged the construction but did not cause any failures," Pirelli said.
Full official statement by Pirelli:
- Technical analysis confirms the absence of any structural problem with the tyres used at the Belgian Grand Prix.
- Tests have shown that the failures at Spa were down to the exceptional combined effect of debris on the track and prolonged tyre usage on a circuit that is particularly demanding.
- At the Belgian Grand Prix there were 63 cuts in the tyres, compared to an average of 1.2 cuts per circuit in the previous 15 events (including races and tests)
- In order to guarantee greater safety, Pirelli proposes with the fia to undertake a study to optimise the way in which circuits are cleaned.
Following the recent technical analysis carried out on the tyres used at Spa, Pirelli concludes that:
- The tests carried out by Pirelli on the tyres used at Spa have confirmed the absence of any structural problems. Pirelli has undertaken in-depth analysis on the materials and production processes used, utilising two different methods of tests and checks. Microscopic analysis, carried out on a large number of the tyres after the second free practice session, showed no signs of fatigue or integrity issues. The same result was confirmed for the tyres used during the race, which were cross-sectioned and analysed in Milan. Some of the tyres used in the race were subjected to a further laboratory fatigue test, passing all the assessments conclusively and confirming that there was no structural degradation or problem on-track. Since the start of 2015, 13,748 slick tyres have been used: including on especially severe tracks like Sepang, Barcelona and Silverstone. No problems have ever been discovered, underlining the fundamental solidity of the product.
- The events of Spa can therefore be put down to external factors, linked with the prolonged use of the tyres on one of the most severe tracks of the championship. The external factors are demonstrated by a total of 63 cuts found in the tread of the Formula One tyres used over the course of the Spa weekend, following numerous incidents that took place during the support races before the Formula One grand prix. In the previous 15 events (10 races and five test sessions) an average of only 1.2 cuts per event were noted. All this indicates an anomalous amount of detritus on the track in Spa, with a consequent increased risk of encountering a foreign object. If even a small piece of debris – made of carbon or any other particularly sharp material – penetrates and cuts the various structural parts of a tyre (which is obviously subject to high-speed use, and more susceptible if used for a prolonged period) without penetrating the actual structure, this can cause a failure that is different to that found in the event of a normal puncture, which is characterised by a loss of tyre pressure. And the former was the type of event seen on Sebastian Vettel’s tyre at Spa.
As for Nico Rosberg, in whose case the tyre usage was less, the tyre held up – as the footage clearly shows – and the failure was not instantaneous. For four corners previously, an element of the internal structure of the tyre was visible, coming out of the tread pattern. This highlighted the existence of the damage and the consequent start of the tyre’s attrition. Throughout the Spa weekend (including practice, qualifying and the race) cuts caused by debris were found on the tyres of other drivers, which damaged the construction but did not cause any failures. - At the end of qualifying on Saturday at Spa, following the exceptional number of cuts noted to the tyres, Pirelli pointed out the condition of the circuit to the FIA and asked for it to be cleaned, as well as for the teams to be told. The FIA reacted promptly in arranging for the track to be cleaned and advising the teams.
Together with the FIA, Pirelli proposes a study to evaluate the way in which circuits can be cleaned most effectively.
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