Rahal lapped the 14-turn, 2.439-mile IMS road course in 1m09.8421s in the 90-minute session for Rahal Letterman Lanigan Racing.
Given IndyCar already raced on the circuit layout in May, track activity was sparse to begin with apart from rookies, who are allowed an extra set of primary tyres.
May’s polesitter Christian Lundgaard led the way for the Rahal team after 30 minutes with a lap of 1m10.4945s, two tenths ahead of Chip Ganassi Racing’s rookie Marcus Armstrong.
Last year’s winner here Alexander Rossi (Arrow McLaren) and series dominator Alex Palou (Ganassi) took turns at the top, both dipping into the 1m10.3s bracket – Palou producing 1m10.3003s, which stood as the quickest time set on the primary tyres.
The red flag flew with 43 minutes to go when Pato O’Ward (McLaren) spun exiting Turn 13 and slid across the grass and stalled his engine.
McLaren’s Felix Rosenqvist was the first to set an alternate-tyred time, a 1m09.9267s, with 20 minutes remaining. That stayed top for a good while, until Graham Rahal produced 1m09.8421s with nine minutes to go.
Josef Newgarden, Team Penske Chevrolet
Photo by: Geoffrey M. Miller / Motorsport Images
Many teams appeared keener on running their alternates long – which are a harder compound this weekend than they were in May – rather than attempting pure qualifying simulations, which probably skewed the pecking order.
“I think the reds have thrown people for a loop, there’s a lot more understeer than before,” said Rahal. “I feel strong.”
Rosenqvist stayed in second, ahead of Lundgaard, Rossi, Palou, the lead Team Penske car of Scott McLaughlin, Scott Dixon (Ganassi), O’Ward, Marcus Ericsson (Ganassi) and Devlin De Francesco (Andretti Autosport).
Toronto’s debutant star Linus Lundqvist lost track time due to an engine problem with his Honda-powered Meyer Shank Racing car. Once rectified, he set the seventh-quickest primary tyre time but fell to 13th on alternates.
Title contender Josef Newgarden could only manage 24th in this session, and admitted it was “not a good practice”.
In IndyCar parish notices, there will be six-place starting grid penalties tomorrow for Helio Castroneves (MSR), David Malukas (Dale Coyne Racing) and Jack Harvey (Rahal Letterman Lanigan Racing) for unapproved engine changes.
Qualifying starts at 12:30pm ET, with a final practice scheduled for 4:00pm ET.
IndyCar Indy RC – Free Practice 1 results