Pipo Derani led the way in opening practice for this weekend’s TireRack.com Grand Prix at Michelin Raceway Road Atlanta, leading a Cadillac 1-2 in the session.
The Brazilian laid down a 1:09.743 in his No. 31 Action Express Racing Cadillac DPi-V.R to edge out the No. 5 JDC-Miller Motorsports entry of Sebastien Bourdais by 0.389 seconds.
Harry Tincknell made a late-session improvement to third in the No. 55 Mazda RT24-P.
The Cadillacs received a late-event Balance of Performance adjustment in the build-up to the second round of the Michelin Endurance Cup.
Three Cadillacs finished the session in the top-four, with the No. 10 Wayne Taylor Racing entry of Renger van der Zande reeling off a 1:10.482.
The No. 77 Mazda DPi of Oliver Jarvis completed the top-five overall in class.
Both Team Penske Acura ARX-05s ran limited laps, with the No. 7 car slotting in sixth, 1.1 seconds off the pace, while the No. 6 car completed only four laps after a turbo issue.
The No. 18 Era Motorsport Oreca 07 Gibson paced LMP2 while Porsche was 1-2 in GT Le Mans, thanks to Earl Bamber’s 1:17.552 in the No. 912 Porsche 911 RSR.
Bamber edged out teammate Fred Makowiecki by 0.014 seconds.
John Edwards was third quickest in the No. 24 Team RLL BMW M8 GTE, ahead of the pair of Chevrolet Corvette C8.Rs, which are riding a four-race win streak.
GT Daytona was topped by the No 44 GRT Magnus Lamborghini Huracan GT3 Evo of Andy Lally, followed by the sister Lamborghini run by Paul Miller Racing.
The No. 96 Turner Motorsport BMW M6 GT3 of Bill Auberlen, who became the winningest driver in IMSA history last time out at Virginia International Raceway, was third on the class time sheets.
Practice 2 is set to get underway at 2:25 p.m. ET, followed by qualifying at 6:35 p.m., which will be streamed live on IMSA.tv.
RESULTS: Practice 1