Scott Dixon set the fastest time of this afternoon's first IndyCar practice session at Chicago.
The reigning champion was quickest in the few laps that were run at the beginning of the session, before a long rain delay halted proceedings.
When running resumed, Dixon set the pace once again and his 217.460mph lap was enough to keep him comfortably ahead of Penske drivers Ryan Briscoe and Helio Castroneves, who finished the session second and third.
Andretti Green team-mates Danica Patrick and Marco Andretti set the fourth and fifth quickest times, with Graham Rahal rounding out the top six.
Last week's race winner Dario Franchitti was only seventh, more than a tenth of a second slower than Ganassi team-mate Dixon, while Tony Kanaan, Mario Moraes and Oriol Servia completed the top 10.
Pos Driver Team Time Speed
1. Scott Dixon Ganassi 25.1633s 217.460
2. Ryan Briscoe Penske 25.2073s 217.080
3. Helio Castroneves Penske 25.2899s 216.371
4. Danica Patrick AGR 25.3001s 216.284
5. Marco Andretti AGR 25.3068s 216.226
6. Graham Rahal Newman/Haas 25.3170s 216.139
7. Dario Franchitti Ganassi 25.3190s 216.122
8. Tony Kanaan AGR 25.3402s 215.941
9. Mario Moraes KV 25.3616s 215.759
10. Oriol Servia Newman/Haas 25.3789s 215.612
11. Justin Wilson Dale Coyne 25.3869s 215.544
12. Ed Carpenter Vision 25.3874s 215.540
13. Dan Wheldon Panther 25.4037s 215.402
14. Raphael Matos Luczo Dragon 25.4349s 215.137
15. Hideki Mutoh AGR 25.4505s 215.006
16. Tomas Scheckter Dreyer & Reinbold 25.4808s 214.750
17. Sarah Fisher Fisher 25.4824s 214.736
18. Ryan Hunter-Reay Foyt 25.5116s 214.491
19. EJ Viso HVM 25.6373s 213.439
20. Mike Conway Dreyer & Reinbold 25.6642s 213.215
21. Milka Duno Dreyer & Reinbold 25.7149s 212.795
22. Robert Doornbos HVM 25.7392s 212.594
23. Jaques Lazier 3G 25.8805s 211.433