The FIA has upheld Lewis Hamilton's Italian Grand Prix victory after an investigation into Mercedes' tyre pressures.
The pressures on the left rear tyres of the cars of Hamilton and Mercedes team-mate Nico Rosberg were found to be under the minimum value - by 0.3 PSI and 1.1 PSI respectively - when the FIA conducted a spot test on the top four cars on the grid on Sunday. As a result, the validity of Hamilton's victory was subject to a stewards investigation, which lasted three hours before a decision was finally reached. After speaking to the team, its Pirelli engineer and FIA technical delegate Jo Bauer it was decided Mercedes had done nothing wrong within the current regulations and therefore the win would stand.
The investigation found that the tyres were at the correct pressures when they were fitted to the car, but that their pressure when checked on the grid five minutes before the start had dropped. It also found that the tyres were well below the maximum tyre blanket temperature allowed, which would have resulted in the pressures dropping ahead of the start.
"Having heard from the technical delegate, the team representatives and the Pirelli team tyre engineer, the stewards have determined that the pressure in the tyres concerned were at the minimum start pressure recommended by Pirelli when they were fitted to the car," the FIA statement read. "In making this determination regarding the pressure, the stewards noted that the tyre warming blankets had been disconnected from their power source, as is normal procedure, and the tyres were significantly below the maximum permitted tyre blanket temperature at the time of the FIA's measurement on the grid and at significantly different temperatures from other cars measured on the grid.
"Further, the stewards are satisfied that the team followed the currently specified procedure, supervised by the tyre manufacturer for the safe operation of the tyres. Therefore, the stewards decide to take no further action.
"Nevertheless, the stewards recommend that the tyre manufacture and the FIA hold further meetings to provide clear guidance to the teams on measurements protocols."
Mercedes team principal Toto Wolff added: "We need to talk about procedures in the future but for this particular incident there is no penalty. We were exactly on the minimum pressures, as we should have been, when the tyres were put on the car.
"I don't know where the discrepancy came from, but it was not a procedural or mistake made by the team in order to gain an advantage.
Asked if he was concerned by the investigation, Wolff added: "When you are called to the stewards you are always nervous, especially after such a [dominant] victory, and having lost Nico's car two laps from the car, so a little bit relieved after that now."