Franco Morbidelli and Johann Zarco left it late on Friday to record the two fastest times of the first day of practice for the Catalan MotoGP.
Both were among the riders who crashed on a wind-buffeted afternoon, but on their final laps became the only two riders to dip under 1min 40sec all day.
Morbidelli, an Italian who rides for Yamaha-SRT, was fastest with Zarco of Ducati satellite Avintia just over one tenth of a second back.
Morbidelli's team-mate, Frenchman Fabio Quartararo had set the best time in the morning but that was surpassed by five riders in the afternoon.
South African Brad Binder was third ahead of Spaniard Maverick Vinales of Yamaha.
The Catalan race is the eighth of 15 in a season which has become highly competitive in the absence of the six-time world champion Marc Marquez (Honda), who broke his arm in the first race.
After posting the second-fastest time in the morning, championship leader Andrea Dovizioso, an Italian with Ducati, was only 18th quickest in the afternoon.
Dovizioso leads Quartararo and Vinales by one point.
A third practice session will take place on Saturday morning before qualifying from 14:10 SA time.
The riders with the ten fastest times from the first three free practice sessions will participate directly in the second qualifying session (Q2), which determines the top 12 places on the grid.
The remaining drivers must participate in a pre-qualifying session (Q1), with the two fastest drivers selected for Q2.
Fastest laps over the first two free practice sessions of the Catalan MotoGP:
1. Franco Morbidelli (ITA/Yamaha-SRT) 1min 39.789sec, 2. Johann Zarco (FRA/Ducati-Avintia) at 0.109, 3. Brad Binder (RSA/KTM) 0.219, 4. Maverick Vinales (ESP/Yamaha) 0.419, 5. Takaaki Nakagami (JPN/Honda-LCR) 0.623, 6. Fabio Quartararo (FRA/Yamaha-SRT) 0.642, 7. Joan Mir (ESP/Suzuki) 0.652,8. Pol Espargaro (ESP/KTM) 0.685, 9. Alex Marquez (ESP/Honda) 0.689,10. Valentino Rossi (ITA/Yamaha) 0.713