Nico Rosberg continued his fine start to the season by topping the timesheets in a Chinese GP first practice session that was disrupted by red flags and punctures.
The German has claimed victory in the first two races of the season, bringing his winning streak to five races, and beat team-mate Lewis Hamilton by just over a tenth of a second with a 1:38.037 in Shanghai on Friday morning.
Ferrari's Sebastian Vettel trailed the Mercedes duo in third, while Fernando Alonso made his return from injury to finish 12th in the McLaren.
However, P1 was overshadowed by two red flags due to rear left tyre problems.
First, Felipe Massa spun off at Turn Six after his tyre came loose, with debris flying off his Williams. Following heavy clean-up work on track and back in the garage the Brazilian returned later on in the session, only to face a failure on the same tyre, at the same corner.
Moments later, Kevin Magnussen was also limping back to the pits with the same rear left tyre shredded.
Pirelli insisted that Massa's issues were not down to simple punctures, instead putting it down to "air loss connected to technical trouble". They later confirmed that the Williams and Renault problems were not tyre related.
While investigations will continue, McLaren engineers suspected that the Williams problem was due to the tyre rubbing against body work, with Magnussen's down to debris on the track.
Massa though, was uncertain. "We had two punctures. Why? I don't know, " he told Sky Sports F1. "We are investigating. For sure, something is touching the tyre or the wheel or whatever.
"We had no idea why we had the first problem. We checked the car and it was ok. But then we had the same problem."
Hamilton, who has been handed a five-place grid penalty for the race, set the early pace on the medium compound - two tenths faster than Rosberg.
However, the world champion was reporting problems as he locked up and span off twice at Turn 11.
Following the 30-minute stoppage due to the second red flag there was a flurry of activity at the end of the session, during which Rosberg edged ahead of his team-mate.
Even Rosberg encountered issues towards the end of the session, which Mercedes diagnosed as an ignition problem.
Vettel could only finish half a second behind the Mercedes as Daniel Ricciardo claimed fourth, with Kimi Raikkonen finishing the session fifth in the other Ferrari.
Alonso, who has been passed fit to take part over the whole weekend despite broken ribs, could only manage five laps.
Jenson Button, meanwhile, ended the session eighth as McLaren decided to make use of their extra supersofts with rain expected to fall on Saturday.
Practice One timesheet
1. Nico Rosberg, Mercedes, 1:38.037
2. Lewis Hamilton, Mercedes, 1:38.183
3. Sebastian Vettel, Ferrari, 1:38.665
4. Daniel Ricciardo, Red Bull, 1:39.061
5. Kimi Raikkonen, Ferrari, 1:39.155
6. Daniil Kvyat, Red Bull, 1:39.625
7. Carlos Sainz, Toro Rosso, 1:39.676
8. Jenson Button, McLaren, 1:39.974
9. Nico Hulkenberg, Force India, 1:40.169
10. Max Verstappen, Toro Rosso, 1:40.232
11. Sergio Perez, Force India, 1:40.347
12. Fernando Alonso, McLaren, 1:40.538
13. Valtteri Bottas, Williams, 1:40.828
14. Romain Grosjean, Haas, 1:41.358
15. Marcus Ericsson, Sauber, 1:41.393
16. Rio Haryanto, Manor, 1:41.614
17. Jolyon Palmer, Renault, 1:41.816
18. Pascal Wehrlein, Manor, 1:42.907
19. Felipe Nasr, Sauber 1:42.980
20. Kevin Magnussen, Renault, No time set
21. Esteban Gutierrez, Haas, No time set
22. Felipe Massa, Williams, No time set
Watch the Chinese GP weekend - LIVE ONLY on Sky Sports F1. The race starts at 7am on Sunday, with build-up underway from 5.30am. Or watch without a contract for £6.99 on NOW TV.