Ryan Briscoe led team-mate Helio Castroneves in a Penske 1-2 after a frenetic end to Friday practice for the Watkins Glen IndyCar round.

For most of the hour Ganassi's Dario Franchitti and Scott Dixon had led the way, as the Penske drivers were late to appear on track. But in the final ten minutes a flurry of rapid flying laps saw constant place changing among the frontrunners, with all three of Penske's entries - Castroneves, Briscoe and Will Power - appearing on top, Dixon briefly nudging back ahead, and Dreyer & Reinbold's Justin Wilson and Panther's Dan Wheldon also fighting in the top three.

Briscoe, who took pole here for the last two years, eventually emerged on top with a 1m31.4142s lap, just 0.0831 seconds ahead of Castroneves. Dixon ended up third, 0.2s off the pace, ahead of a startling performance from Wheldon and last year's Watkins Glen race-winner Wilson. Power and Franchitti were pushed back to sixth and seventh.

De Ferran Dragon's Raphael Matos showed strongly in eighth ahead of Tony Kanaan in the top Andretti Autosport car. The latter was, along with FAZZT's Alex Tagliani, one of two drivers to require a yellow after problems on track necessitated a tow back to the pits.

Mario Moraes completed the top ten for KV Racing. Further back, Paul Tracy was 16th in his first session with Dreyer & Reinbold, while Adam Carroll's IndyCar career got off to a quiet start with 23rd for AFS/Andretti.

1. Ryan Briscoe Penske 1m31.4142s 
2. Helio Castroneves Penske 1m31.4974s + 0.0831s 
3. Scott Dixon Ganassi 1m31.6781s + 0.2638s 
4. Dan Wheldon Panther 1m31.7830s + 0.3687s 
5. Justin Wilson Dreyer & Reinbold 1m31.8627s + 0.4485s 
6. Will Power Penske 1m31.9317s + 0.5174s 
7. Dario Franchitti Ganassi 1m31.9895s + 0.5753s 
8. Raphael Matos De Ferran Dragon 1m32.1616s + 0.7474s 
9. Tony Kanaan Andretti 1m32.1877s + 0.7735s 
10. Mario Moraes KV 1m32.2569s + 0.8426s 
11. Marco Andretti Andretti 1m32.4116s + 0.9974s 
12. Ryan Hunter-Reay Andretti 1m33.0287s + 1.6144s 
13. Hideki Mutoh Newman/Haas 1m33.0661s + 1.6518s 
14. EJ Viso KV 1m33.1804s + 1.7662s 
15. Mario Romancini Conquest 1m33.2247s + 1.8104s 
16. Paul Tracy Dreyer & Reinbold 1m33.2985s + 1.8843s 
17. Danica Patrick Andretti 1m33.3267s + 1.9124s 
18. Takuma Sato KV 1m33.3399s + 1.9256s 
19. Simona de Silvestro HVM 1m33.5173s + 2.1031s 
20. Alex Lloyd Dale Coyne 1m33.6884s + 2.2741s 
21. Alex Tagliani FAZZT 1m34.2046s + 2.7903s
22. Vitor Meira Foyt 1m34.2437s + 2.8295s
23. Adam Carroll AFS/Andretti 1m34.4028s + 2.9885s 
24. Bertrand Baguette Conquest 1m35.7741s + 4.3599s 
25. Milka Duno Dale Coyne 1m37.2840s + 5.8697s