Sam Schmidt Motorsports/AFS Racing's Martin Plowman put a set of the "red walled" soft option tyres to good use by topping the timesheet at the end of hour-long Saturday morning practice session. His time of 1:19.0350s pipped Dario Franchitti by just 0.004s in only the second IndyCar weekend of his career.
The red tyres appeared to provide a boost of around 2s over the harder "black-walled" compound tyres on this 12-turn 2.52-mile natural-terrain course; by comparison, Plowman had been 20th at the end of Friday's sole practice session. Meanwhile Franchitti and Will Power (a further 0.0013s back) were running on the harder tyres and saving their softer reds for the afternoon qualifying session for the Indy Grand Prix of Sonoma at Infineon Raceway in California.
Other than Plowman, JR Hildebrand and James Jakes also put runs on the red tyres to good use, ending up with with the fourth and fifth fastest times of the session just ahead of Scott Dixon and Ryan Briscoe who were keeping to the black tyres for practice. After the Friday session, Hildebrand had been in 19th while Jakes had finished in tenth position.
Everyone was testing and pushing to the very edge of the track, car and their personal limits, with many drivers having an occasional run-off including Will Power, Tony Kanaan, Ana Beatriz and Alex Tagliani. There were early cautions for Ana Beatriz, who slid off at turn 4 and needed a push start to recover to the pits; and Ryan Hunter-Reay who spun around at turn 3 around 15 minutes into the session, ending up facing the oncoming traffic. Beatriz triggered another caution near the end of the session when she too spun in turn 3 and stalled the engine in the process, potentially derailing anyone with ideas of making a late flying lap at the end of the session.
Renault F1 test driver Ho-Pin Tung - also on reds - impressed again with 11th place for Schmidt Dragon Racing in the timings, on his first return to the series after the ill-fated attempt to make the Indianapolis 500 starting grid in May.
Simon Pagenaud was 24th as he continued to car-sit for the absent Simona de Silvestro, whose via and immigration problems seem set to rule her out of this week's race and may even threaten her participation at next week's maiden Baltimore street race.
According to reports, an immigration official in New York questioned de Silvestro about her recent multiple trips to Canada (for the Toronto and Edmonton races) when she returned to the US from visiting family in Switzerland. When she responded that she was an IndyCar driver, he refused to believe her, decided that she was using an assumed name, voided her visa and put her on a plane back to Switzerland.
Qualifying takes place at 2.35pm local time (10.35pm BST) and will start with the field split into two 14-car groups with the top six times from each progressing through to the next round, and the top six from round 2 entered into the Firestone Fast Six pole shootout.
Group 1 consists of Will Power, Scott Dixon, Sebastien Bourdais, EJ Viso, James Jakes, Ryan Hunter-Reay, Graham Rahal, Ryan Briscoe, Mike Conway, Martin Plowman, Tony Kanaan, Sebastian Saavedra, Danica Patrick and Ed Carpenter.
Group 2 consists of Dario Franchitti, Helio Castroneves, Giorgio Pantano, Ana Beatriz, Oriol Servia, James Hinchcliffe, Charlie Kimball, Marco Andretti, Ho-Pin Tung, JR Hildebrand, Alex Tagliani, Takuma Sato, Simon Pagenaud and Vitor Meira.
Full Saturday practice times