Italian Grand Prix: Mercedes blame tyre 'procedure' for issues

Mercedes blamed a lack of clarity about tyre-testing procedure for the controversy surrounding Lewis Hamilton at the Italian Grand Prix.

Hamilton's victory was in doubt for a couple of hours after it emerged one of his tyres was below the minimum recommended pressure before the race.

But stewards took no action following an investigation that established Mercedes had operated the car safely.

"It is about the procedure when you measure the tyre," Toto Wolff said.

Wolff, Mercedes' F1 boss, said the team had correctly followed the procedure for measuring the tyre pressures established by manufacturer Pirelli but that they had been measured by governing body the FIA outside the stipulated period.

The FIA referred the issue to the race stewards after Hamilton's left-rear tyre was found to be 0.3psi below the minimum requirement, after the signal indicating five minutes to go before the start of the race.

But Wolff said the procedure agreed with Pirelli had been to measure the pressure before that.

"We followed the procedure established with Pirelli, which was to have the tyres in the blankets, check the pressures together with Pirelli," Wolff said.

"The pressures were well above the minimum because safety is important for us. The tyres on the car - for whatever reason, maybe because the tyres cooled down - a different pressure was found on one of the tyres. It was a tiny discrepancy."

The stewards said in their verdict that the electric blankets that maintain the tyre pressures had been disconnected.

Wolff said that the FIA needed to make clear a specific procedure that was clear to all before the next race in Singapore on 18-20 September.

He also said he could "absolutely rule out" any attempt to let the tyre pressure drop before the race in search of a performance advantage.

A higher pressure limit was set by Pirelli for the Italian race after two high-speed failures at the previous race in Belgium.

"We have worked the whole week after Spa with Pirelli to find solutions in order to make those tyres safe," Wolff said.

"We were very much part of trying to guide them on minimum tyre pressures and minimum camber, which we already had on our car at Spa.

"So I can rule out that we would be the ones who were trying to gain an advantage in a way which is absolutely unscientific and uncontrollable."

Hamilton's team-mate Nico Rosberg was also found to have a too-low tyre pressure - by 1.1psi in his case.

The German retired from the race with an engine failure while running third with two laps to go.

Hamilton leads Rosberg in the championship by 53 points with 175 still available over the remaining seven races.

Race results