Sebastian Vettel headed teammate Mark Webber as Red Bull scored an impressive 1-2 in a dry second Belgian Grand Prix practice session.
Vettel's session ended on a sour note however when he suffered a right-rear puncture 20 minutes from the flag, after a long run on the medium compound. He ended up shredding the tire as he limped back to the pits.
Pirelli has brought its hardest two compounds to Spa in order to deal with the extreme loads posed by the Belgian circuit, and has prescribed restrictive limits on pressures and cambers. It was an unfortunate end for Red Bull given its domination of proceedings.
Vettel and Webber hit the front early on and then extended their advantage once the field switched onto Pirelli's medium compound, eventually ending the session more than seven tenths clear of the chasing pack.
Vettel had also been fastest on the hard tire, and was only displaced when Webber switched onto the options compound and dropped down to a 1m49.390s. He responded instantly however, reasserting himself at the head of the timesheets with a 1m49.331s that was enough to secure top spot given teams switched their focus onto long runs shortly after.
Only four men – Romain Grosjean, Felipe Massa, Jean-Eric Vergne and Kimi Raikkonen – were able to get within one second of Vettel's benchmark. Fernando Alonso, who went briefly fastest early on for Ferrari, beat McLaren's Sergio Perez and Mercedes' Nico Rosberg to seventh.
Force India pair Paul di Resta and Adrian Sutil meanwhile locked out 10th and 11th ahead of Hungarian GP winner Lewis Hamilton, who struggled with the handling of his Mercedes throughout.
Nico Hulkenberg, Pastor Maldonado, Jenson Button and Daniel Ricciardo were next up, with the latter more than 1.2sec slower than teammate Vergne.
Giedo van der Garde, meanwhile, caused the only incident of the session when he lost the rear of his Caterham and slewed into the barriers exiting the Stavelot-Paul Frere complex. The Dutchman, who ended the session in 19th, was unhurt.
Pos Driver Team/Car Time Gap Laps
1. Sebastian Vettel Red Bull-Renault 1m49.331s 22
2. Mark Webber Red Bull-Renault 1m49.390s +0.059s 34
3. Romain Grosjean Lotus-Renault 1m50.149s +0.818s 34
4. Felipe Massa Ferrari 1m50.164s +0.833s 27
5. Jean-Eric Vergne Toro Rosso-Ferrari 1m50.253s +0.922s 28
6. Kimi Raikkonen Lotus-Renault 1m50.318s +0.987s 33
7. Fernando Alonso Ferrari 1m50.510s +1.179s 21
8. Sergio Perez McLaren-Mercedes 1m50.536s +1.205s 27
9. Nico Rosberg Mercedes 1m50.601s +1.270s 33
10. Paul di Resta Force India-Mercedes 1m50.611s +1.280s 27
11. Adrian Sutil Force India-Mercedes 1m50.629s +1.298s 30
12. Lewis Hamilton Mercedes 1m50.751s +1.420s 27
13. Nico Hulkenberg Sauber-Ferrari 1m50.972s +1.641s 33
14. Pastor Maldonado Williams-Renault 1m50.991s +1.660s 28
15. Jenson Button McLaren-Mercedes 1m51.195s +1.864s 28
16. Daniel Ricciardo Toro Rosso-Ferrari 1m51.447s +2.116s 26
17. Valtteri Bottas Williams-Renault 1m51.568s +2.237s 28
18. Esteban Gutierrez Sauber-Ferrari 1m51.644s +2.313s 26
19. Giedo van der Garde Caterham-Renault 1m53.157s +3.826s 21
20. Charles Pic Caterham-Renault 1m53.251s +3.920s 29
21. Jules Bianchi Marussia-Cosworth 1m53.482s +4.151s 28
22. Max Chilton Marussia-Cosworth 1m54.418s +5.087s 12