MILAN—Pirelli Tyre S.p.A. is laying the blame for two high-speed tire failures at the Belgium Grand Prix in August on external factors such excessive debris on the track and prolonged tire usage on a particularly demanding circuit.
In its analysis, Pirelli said it observed 63 cuts in tires throughout the three-day race weekend, a 50-fold increase over the average of 1.2 cuts per event through the first 15 races of the 2015 season.
The failures—on Nico Rosberg's Mercedes F1 during practice and Sebastian Vettel's Ferrari F1 in the late stages of the race—both initiated in the same section of the Spa, Belgium, circuit, immediately after the famous “Eau Rouge” curve.
The failures turned into a public spat immediately after the Aug. 23 event, pitting Pirelli against a number of F1 teams. Rival tire maker Group Michelin weighed in as well, trying to make its case to replace Pirelli as the series tire supplier.
The Federation Internationale de l'Automobile, Formula 1's sanctioning body, declared in a statement that it is “satisfied with the thoroughness of the investigation and Pirelli's conclusions as to the reasons for the tire failures in Belgium.”
Based on Pirelli's investigation, the FIA declared it is willing to consider “any safety recommendations made by the tire supplier for the Italian GP and for the remainder of the season.”
In its statement, Pirelli said it is proposing the FIA evaluate the way circuits can be cleaned effectively. The tire maker noted that racing's increased use of carbon fiber in racing car components can leave small extremely sharp shards of the material after accidents.
Pirelli has designated the same pair of tire types for this weekend's Italian Grand Prix at Monza—also a high-speed circuit, with average lap speeds approaching 160 mph—as were used at Spa.
In its statement, Pirelli said its investigation, which involved laboratory microscopic analysis and high-speed fatigue testing, “confirmed the absence of any structural problems” in tires used at Spa.
At the Belgium Grand Prix, Rosberg eventually spun off course while Vettel was able to drive his car back to the pits, although the failure cost the four-time F1 world champion an almost certain third-place finish at the race. Pirelli noted that in Vettel's case, the Ferrari team had opted to run the tires for several laps beyond its recommendation for that type tire, making the tire “more susceptible to damage from even small pieces of debris.”
Michelin's sports chief Pascal Couasnon weighed in on the situation in the days after the event, reportedly telling a German newspaper, “One thing I can tell you is, it makes no sense to us to produce tires that last 10 laps. A Formula 1 tire should manage at least one third of the race, and perhaps two-thirds.”
Michelin and Pirelli both submitted bids earlier this year to be Formula 1's designated tire supplier for the 2017-19 seasons.
Pirelli has been F1's designated race tire supplier since the 2011 season.
Both companies have stated they would like to see Formula 1 move away from its current 13-inch rim diameter specification to an 18-inch spec.
The FIA is expected to make its decision on the 2017-19 contract in the coming four or five weeks, Couasnon said.
Autoweek Magazine, a Detroit-based sister publication of Rubber & Plastics News, and Global Motorsport Media contributed to this report.