Several drivers ended up in run-off areas during the session as drivers experimented with brake zones, using the softer alternate Firestone tires as well as the primaries, struggling to get their brake balance adjusted.

Felix Rosenqvist locked up his rears which stalled the Chevrolet engine in his Arrow McLaren SP, but he avoided contact with the barriers. Rinus VeeKay spun and knocked the rear wing off his Ed Carpenter Racing-Chevy.

But then with under two minutes to go, Johnson took a wild ride coming off the bridge at Turn 4, the #48 Chip Ganassi Racing-Honda appeared to snap into oversteer at 170mph, spinning backward and making hard contact with the right-rear tire against the left-hand wall.

Johnson sounded surprised and perplexed by the accident, but alighted from his car without help. With the race still four hours away, the damage did not look substantial enough to cause the Ganassi team major problems in fixing for the race.

The other three CGR-Hondas looked strong during the half-hour session, with Scott Dixon, Alex Palou and Marcus Ericsson finishing second, fifth and sixth.

But they were all beaten by Graham Rahal, who will start 13^th and believes the Rahal Letterman Lanigan Racing-Honda team has substantially improved his car’s handling in low-speed turns, where he lost most to polesitter Colton Herta during qualifying.

Pato O’Ward slotted his Arrow McLaren SP into third ahead of his former Indy Lights teammate Herta, while Nashville’s own Josef Newgarden was fastest of the Penske-Chevrolets in seventh.

As in qualifhing, Jack Harvey (Meyer Shank Racing-Honda) and Romain Grosjean (Dale Coyne Racing with RWR-Honda) were inside the top 10.

Sebastien Bourdais who witnessed close-at-hand the Johnson shunt, finished the session in 11^th, just behind Penske’s Simon Pagenaud.

Engines fire for the inaugural Big Machine Music Grand Prix at 4.38pm local (Central) time.