Ganassi starts Iowa weekend on top

The reigning champion took the top spot from team-mate Dario Franchitti soon after the session - which as usual began with additional practice for rookies and drivers outside the championship top ten - was opened up to the frontrunners.

Marco Andretti was third on the timesheets, but faces a difficult weekend after suffering a big crash on his 26th lap of the morning. The Andretti Green driver reckoned that "something broke" on his car after he spun into the Turn 2 wall. The heavy impact wrecked his primary car and left the team to prepare his back-up chassis for the rest of the event.

The session was stopped for ten minutes while Andretti's debris was cleared up, and his time stood for third place when running resumed for a final quarter of an hour. His team-mate Tony Kanaan took fourth, with the two Penske Dallara-Hondas fifth and seventh, split by Panther's Dan Wheldon.

A strong start to the weekend for Dreyer & Reinbold Racing saw Tomas Scheckter and Mike Conway take ninth and 11th, with the British rookie having been fastest in the opening 45 minute segment before the leading drivers joined in.

Ryan Hunter-Reay was 16th on his first appearance driving for AJ Foyt Enterprises. With Vision scaling back to a single car after his move, and the Iowa race not featuring in Sarah Fisher, Milka Duno or Conquest's programmes, the field is down to just 20 cars for this weekend.

Pos  Driver             Team                 Time      Gap
 1.  Scott Dixon        Ganassi              17.7135s
 2.  Dario Franchitti   Ganassi              17.7498s  + 0.0363s
 3.  Marco Andretti     Andretti Green       17.7920s  + 0.0785s
 4.  Tony Kanaan        Andretti Green       17.8025s  + 0.0890s
 5.  Ryan Briscoe       Penske               17.8192s  + 0.1057s
 6.  Dan Wheldon        Panther              17.8223s  + 0.1088s
 7.  Helio Castroneves  Penske               17.8243s  + 0.1108s
 8.  Danica Patrick     Andretti Green       17.8385s  + 0.1250s
 9.  Tomas Scheckter    Dreyer & Reinbold    17.8499s  + 0.1364s
10.  Graham Rahal       Newman/Haas/Lanigan  17.8530s  + 0.1395s
11.  Mike Conway        Dreyer & Reinbold    17.8701s  + 0.1566s
12.  Mario Moraes       KV                   17.8814s  + 0.1679s
13.  Ed Carpenter       Vision               17.9178s  + 0.2043s
14.  Robert Doornbos    Newman/Haas/Lanigan  17.9323s  + 0.2188s
15.  EJ Viso            HVM                  17.9335s  + 0.2200s
16.  Ryan Hunter-Reay   Foyt                 17.9415s  + 0.2280s
17.  Hideki Mutoh       Andretti Green       17.9709s  + 0.2574s
18.  Raphael Matos      Luczo Dragon         18.1397s  + 0.4262s
19.  Justin Wilson      Coyne                18.6046s  + 0.8911s
20.  Jaques Lazier      3G                   18.7945s  + 1.0810s