Monza, Italy - 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 One supplier Pirelli said on Thursday.
“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,” the tyre supplier said in a statement at the Italian Grand Prix.
The company proposed, with the FIA governing body, 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.
Pirelli has recommended changes to pressures and camber for Sunday's Italian Grand Prix at Monza, which is the fastest circuit on the calendar and one where cars hit speeds in excess of 360km/h. Drivers expected an increase from 18 PSI (pounds per square inch) to 22 on the front and 21 on the rear, or even as much as 23 and 22 respectively.
“NO STRUCTURAL PROBLEM”
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.
DRIVERS REACT
Following the Pirelli statement, Lewis Hamilton warned of potential “disaster” if tyre pressures were increased substantially.
“In terms of putting the pressures up I don't personally think it's the right way,” Hamilton told reporters.
“I don't think any of us have tried five PSI more on these tyres because they're not designed to have five PSI more.
“We would be moving out of the optimum range of the tyre, we'll be using a different part of the tyre which means there will be more wear, less grip. It's going to be a disaster. So I hope they don't put five PSI more. A couple is OK.”
Vettel said in the immediate aftermath of the race at Spa, when his tyre exploded on the penultimate lap, that the failures were unacceptable.
The four-times world champion, preparing for his first Italian race as a Ferrari driver after moving from Red Bull, moved to mend fences on Thursday even if he stuck to his original statement.
“I think it is not acceptable to have a blowout at that sort of speed, out of the blue,” Vettel told a news conference.
“But I think the investigations that have been going on, the stuff that obviously has been analysed and talked about, explains some of it, maybe not all of it yet but it's still ongoing.
“The most important thing is that we make sure that we make progress. At the moment, from Pirelli's side, it looks very, very professional, they handle it with extreme care, and I think things are going the right way.”
The governing FIA said it was satisfied with Pirelli's explanations while the commercial rights holder also expressed full confidence in the sole supplier bidding for a new three-year deal.
“We are entirely satisfied Pirelli was not at fault for any tyre-related incidents during...the Belgian Grand Prix,” Formula One Management said in a statement.
Reuters