Sauber questioned Pirelli's selection of tyres for the United States Grand Prix following the first day of running at the Circuit of the Americas.
The all-new circuit witnessed plenty of spins during the two 90 minute sessions as drivers tried to find any kind of grip.
Speaking afterwards, Sauber's head of track engineering, Giampaolo Dall'Ara admitted that the tyres had been the biggest challenge for the team to deal with in practice – aside from a broken exhaust on the car of Kamui Kobayashi which was replaced in FP2.
“Given that this track is all new, we produced a different programme for the two cars in order to cover as many variables as possible,” he said. “Although we had a broken exhaust on Kamui's car we managed to complete our task list. The biggest challenge is to get the tyres to work, as they are definitely too hard for the circuit. Otherwise everything went fine today.”
Kobayashi himself, who was ninth quickest over the two sessions, admitted that grip had been an issue throughout the day.
“The high-speed corners of the new circuit are very enjoyable, I really like driving here,” he said. “The first session was about getting familiar with the track and waiting for the tarmac to improve for a better grip level.
“I must say I have big warm up problems with both compounds. It just doesn't work in qualifying if you need ten laps to get the tyres to work. We will now go and look for solutions.”
Team-mate Sergio Perez, who was struggling with the balance of his car, was 14th quickest.