Mercedes driver Lewis Hamilton even complained about a headache after first practice and quipped he may need a cushion to ease the extra pressure on the spine. Photo: Jerome Miron/USA TODAY Sports

Austin  Drivers are not impressed with the state of the Circuit of the Americas after the first two rounds of practice Friday for the United States Formula One Grand Prix, with world champion Lewis Hamilton and ex-champ Sebastian Vettel among those complaining about bumps.

The track is not in the best shape because of its bumps," Ferrari's Vettel said. "But it is what it is and that makes it a bit special and more tricky for us. But I don't think they can do anything to fix it now.

"A bump here and there are part of a circuit's character. But here there are some which look more like a jumping hill."

Mercedes driver Hamilton even complained about a headache after first practice and quipped he may need a cushion to ease the extra pressure on the spine.

"The track was very bumpy in certain areas, especially through Turns 5 and 6 - which is a high-speed section, so if the rear end of the car is not stable enough because of the bumps it can be tough," Hamilton said.

It was not clear why the track had become so bumpy compared to previous years but Vettel said that work needs to done ahead of next year's race.

Final practice and qualifying are later Saturday and the race Sunday. Hamilton has a record five wins in Austin but only needs an eighth-place finish to clinch a sixth world title with two races to spare in the season.

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