SAO PAULO (Reuters) – Triple Formula One world champion Lewis Hamilton hinted on Sunday that a change of tyre pressures may have contributed to the end of his qualifying dominance and team mate Nico Rosberg’s late-season resurgence.

“From Singapore onwards there’s been a change to the car — but whether or not that’s made a difference, I don’t know really,” Hamilton told reporters after finishing second to Rosberg in Sunday’s Brazilian Grand Prix.

“We’ll have to see. But it has changed since Singapore.”

Hamilton has not been on pole position since the Italian Grand Prix at Monza in September, with Ferrari’s Sebastian Vettel taking the top slot in Singapore and Rosberg the following five.

At that same Italian race won by Hamilton, Mercedes faced a stewards’ enquiry after their cars were found to have tyre pressures below the minimum specified by Pirelli after high-speed blowouts at the previous race in Belgium.

With some rivals calling for the champion to be disqualified, Rosberg having failed to finish, the stewards ruled Mercedes had followed the specified procedures and decided to take no further action.

They did however call for clear guidance for future measurements.

Rosberg was more sceptical when asked if the change in pressures from Italy onwards had made a difference.

“I don’t think so. I think I’ve just raised my game. That’s it,” said the German.

(Writing by Alan Baldwin in London, editing by Ian Chadband)