Lewis Hamilton says changes made to his car between practice sessions at the United States Grand Prix took the setup in the wrong direction, and leave him with work to do to get it where he needs it for the rest of the weekend.

Valtteri Bottas topped the times in FP1, edging out Hamilton by just 0.045s in a session where the two Mercedes drivers were nearly a second clear of the rest of the field. That strong start didn’t continue, as Sergio Perez was quickest in the afternoon session with Hamilton third behind Lando Norris, and the defending champion felt less comfortable with his car as the day went on.

“Generally, it’s been a good day but still work to do unfortunately,” Hamilton said. “Well, not unfortunately, it’s the way it is. P1 was really good session, made some changes and I wasn’t happy in P2. And still not such bad pace, but I think we lost some ground to everyone or they gained ground. So we have some work to do tonight, as always.”

High temperatures added to the challenge on Friday but Hamilton believes even if it was cooler the teams would be struggling with tire wear more in Austin this year.

“I don’t think it’s the heat necessarily. I think it’s literally just the track surface is rougher than before and yeah, the tires are… it’s a struggle to keep temperature out of the tires, it’s impossible pretty much, so there’s more deg than we probably experienced before.

“Definitely it’s difficult because you’re actually trying to get a quali setup, and also a setup that will work on the long run, and it’s not easy. It’s not an easy car to set up in general, but I think there was plenty of findings from today, we should be able to navigate well.”

With Bottas taking a five-place grid penalty for using a sixth internal combustion engine (ICE) – his third in four races – Hamilton said he’s not worrying about potentially earning a further penalty himself this season after taking a fresh ICE in Turkey.

“Right this minute I’ve got a new engine, so I’m just… right now just keeping my mind set on one race at a time,” he said.