Aleix Espargaro put Suzuki at the top of the timesheets during opening practice in Argentina.

The Spaniard set a best lap time of 1m 40.806s (1.6s from the race lap record) on his 12th of 16 laps to finish 0.573s clear of Ducati's Andrea Iannone. Iannone was forced to spend the session on his spare GP15 after an early engine failure.

Team-mate Andrea Dovizioso was third (+0.721s), with Columbian Yonny Hernandez delighting the South American fans with fourth (+0.979s) for Pramac Ducati.

Related Articles

Scott Redding put the Texas controversy behind him with fifth place - as the top Honda rider - for the Marc VDS team. The Factory Honda and Yamaha team riders, led by world champion Marc Marquez, were no higher than tenth after apparently opting to save tyres on the dusty track.

That allowed a surprise top ten to continue with Nicky Hayden an excellent sixth (+1.126s) on his Open class Aspar Honda. Espargaro's rookie team-mate Maverick Vinales led the session on his way to seventh.

Avintia's Mike di Meglio put the Open Desmosedici eighth while LCR Honda rookie Jack Miller was also classified ahead of Marquez in ninth. The Repsol Honda star set a best lap 1.799s behind Espargaro on his fifth of 14 laps.

Rossi was the top Movistar Yamaha in 14th (+2.567s) this morning, with team-mate Jorge Lorenzo just 20th (+3.944s).

Qatar winner Rossi starts round three with a one-point title lead over Dovizioso, with Marquez five points back following victory last Sunday in Austin.

This weekend marks MotoGP's second visit to the Termas de Rio Hondo circuit. Marquez won last year's inaugural race from pole position, but had to fight his way through after struggling in the early laps.

Bridgestone is debuting a new extra-hard specification rear slick specifically for this circuit, marked with a yellow line, however it did not appear to be used this morning.

The tyre rules mean it will only be available to the Factory class Honda and Yamaha riders, alongside an asymmetric hard rear compound. The Open class plus Ducati, Suzuki and Aprilia competitors have the medium and hard rears to choose from, which could be a disadvantage on what is usually a highly abrasive surface.

"The circuit itself is fast, flowing and demanding on tyres and the data we acquired last year has enabled us to develop a revised tyre allocation for this year's race, including a new extra-hard specification rear slick," said Bridgestone Motorsport manager Hiroshi Yamada.

The circuit is unusual in that, although there are nine right-hand corners compared to five left, the left shoulder of the tyre experiences higher temperatures than the right, due to the left-handers generally being faster.

Aprilia's Marco Melandri was the only faller, returning to claim 19th on his RS-GP.

Free Practice 1:
1. Aleix Espargaro
2. Andrea Iannone
3. Andrea Dovizioso
4. Yonny Hernandez
5. Scott Redding
6. Nicky Hayden
7. Maverick Vi?ales
8. Mike Di Meglio
9. Jack Miller
10. Marc Marquez
11. Alvaro Bautista
12. Hector Barbera
13. Alex De Angelis
14. Valentino Rossi
15. Pol Espargaro
16. Cal Crutchlow
17. Danilo Petrucci
18. Eugene Laverty
19. Marco Melandri
20. Jorge Lorenzo
21. Karel Abraham
22. Bradley Smith
23. Hiroshi Aoyama
24. Stefan Bradl
25. Loris Baz