MotoGP championship leader Jorge Lorenzo admitted he was struggling to find the right setup for the Indianapolis circuit after ending Friday practice 0.7sec away from pacesetter Dani Pedrosa's Honda.
Lorenzo was still third on the times with his Yamaha, but conceded it had been a tough Friday.
"We were better this afternoon than this morning. We managed to get closer to the first position," he said. "I didn't feel great on the track today so I hope we can improve the feeling for tomorrow. This track seems to be quite difficult for us to find a good set-up. I'm struggling on the entry to the corners where I don't seem to have much grip."
Team manager Wilco Zeelenberg said the difficult track conditions were affecting Lorenzo particularly badly.
"A difficult day, the grip is not as good as on other tracks but that's the same for everybody, it just seems we struggle a little more," he said. "Normally Jorge is very consistent because he can understand a track; here at the moment the track is good in parts and then bad in parts which is quite confusing for his rhythm. Anyway we improved a lot from the morning but we need to make some more steps tomorrow."
While Lorenzo struggled, his teammate Ben Spies was Pedrosa's closest challenger, lapping 0.2sec off the Honda in second place.
"The bike is working really well, we made some small changes then just worked on race setup," said Spies. "We used hard tires for the whole time and were able to set our fastest lap and be consistent with a lot of laps on the tires which is encouraging.
"We'll try the softer tires tomorrow to see if we can pick up some speed for qualifying but for the race set-up the bike is good."