F1 must clear up tyre rules after Italian GP - Mercedes' Toto Wolff

Lewis Hamilton's Italian Grand Prix victory was under threat when his left-rear tyre, along with team-mate Nico Rosberg's, was found to be below Pirelli's limit.

However, the stewards ruled they were satisfied the team followed the currently specified procedure, supervised by the tyre manufacturer for safe operation of tyres.

Wolff said the time when tyre pressures are checked, which on Sunday was after the five-minute signal before the race, should be specified.

"The question is about the procedure," said Wolff. "We check them when we put them on the car.

"You could say when is the moment you should actually check them - five minutes, eight minutes before?

"It is about defining the procedure on when the tyres are checked in the future so it's the same for everybody."

Wolff categorically denied his team deliberately setting pressures so they would meet the requirement at the time of testing but drop lower by the start of the race.

"I can absolutely rule that out," he said.

"We have worked the whole week after Spa with Pirelli in order to make the tyres safe.

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

"So I can rule out that we would try to gain an advantage in a way that is unscientific and uncontrollable.

"How do you measure how much a tyre pressure drops when you disconnect it - and why would you only have it on one tyre and with discrepancies on two cars?"

Wolff said the reason the team had asked Hamilton to push was to generate a margin should the team be penalised, once it learned about the investigation.

He said: "In terms of asking Lewis to push, when we got the message that there was an investigation into tyre pressures, we didn't understand what was going on.

"There could have been possible penalties, so in order to gain a little bit of a margin we asked him to push."