MotoGP title leader Jorge Lorenzo improved from eighth to third during the Friday practice sessions at Indianapolis.
But the Factory Yamaha star is still seeking grip after being left 0.719s behind countryman and nearest title rival Dani Pedrosa. Lorenzo's team-mate Ben Spies was second quickest.
“We were better this afternoon than this morning,” said Lorenzo, who had languished 1.4s off the pace in FP1. “We managed to get closer to the first position. 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 admitted the lack of grip seemed to hurt them more than other riders.
“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.”
Lorenzo, who finished fourth at Indy last season, holds a 23-point lead over Pedrosa.