Will Power and Team Penske set the pace as practice got underway around the streets of Belle Isle on Friday.
The Australian set a best time of 1:15.0197 to beat the lap record he set during qualifying a year ago around the Detroit circuit, but it will not replace last years lap as the new track best as it has to be set during either qualifying or the race.
Power led a Team Penske 1-2 ahead of team-mate Helio Castroneves, with the Brazilian over half a second adrift, while Scott Dixon took third for Chip Ganassi Racing ahead of current championship leader Simon Pagenaud, also of Team Penske.
James Hinchcliffe, pole sitter for last weekend’s Indianapolis 500, was fifth for Schmidt Peterson Motorsport, and was the final driver to set a time beneath the 1:16 barrier, while just outside that time was Graham Rahal in the sole Rahal Letterman Lanigan Racing entry.
Sebastien Bourdais of KVSH Racing, Josef Newgarden of Ed Carpenter Racing and Andretti Autosport duo Marco Andretti and Carlos Munoz completed the top ten.
It was a difficult session for Mikhail Aleshin, who caused two red flags for different issues, with the Russian spinning his Schmidt Peterson Motorsport machine at turn four before then hitting the barrier at turn seven, with the stewards forcing him to sit out the final ten minutes of the session.
Indianapolis 500 winner Alexander Rossi turned his first laps around the Detroit circuit during the session, with the American finishing nineteenth fastest in his Andretti Herta Autosport entry.
Belle Isle Free Practice 1 Result
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