IMSA’s Detroit weekend got underway on Friday with Earl Bamber and the No. 31 Whelen Cadillac setting the pace in both practice sessions, while Corvette Racing led the way in GTD PRO. On the tight 1.7-mile street circuit, the margins were close, but mistakes were costly as several drivers found trouble before the field turned its focus to qualifying.

Free Practice 1

Earl Bamber topped the charts on Friday morning in the opening 90-minute session. The Kiwi turned a lap time of 1:07.182 in the No. 31 Whelen Cadillac. Top 4 cars in GTP, all different manufacturers, were within half a second. The No. 24 BMW, driven by Dries Vanthoor, was second in the session. Nick Yelloly turned the third quickest time in the No. 93 Meyer Shank Racing Acura. Felipe Nasr in the Porsche Penske Motorsport No. 7 rounded out the Top 4.

In GTD PRO, Nicky Catsburg in the No. 4 Corvette lead the session with a 1:11.104. Ben Barnicoat was second in the Vasser Sullivan No. 14 Lexus, less than a tenth off the Corvette. Laguna Seca winner Frederic Vervisch in the No. 65 finished the session third while Alexander Sims in the second Corvette was fourth.

The session was stopped twice, first for debris just past the halfway mark of the session. The second red flag came with 16 minutes remaining when Sandy Mitchell stopped in the Turn 3 runoff. The No. 9 Pfaff Lamborghini did not restart and the red flag had to be displayed to get the car moved. By rule, the No. 9 will lose its fastest lap in qualifying.

While the red flag came from Turn 3, another area that caused trouble was Turn 8. Tijmen van der Helm, Jack Hawksworth and Dries Vanthoor among others all had offs at the penultimate corner, but all were able to continue without trouble.

Corvette Racing also swept the Practice Sessions with the No. 3 (pictured in 2025) leading the second practice Photo Courtesy: Corvette Racing/Team Chevy/GM Motorsports

Free Practice 2

In the midday session, it was same song second verse led by the Whelen Cadillac. Earl Bamber turned the fastest lap with fifteen minutes remaining in the two-hour session with a 1:06.412. Unlike the morning practice with the top 4 inside half a second, the midday session saw the top 8 in GTP within half a second. The WRT BMWs rounded out the top 3 in FP2 with Sheldon van der Linde in No. 24 over Marco Wittman in No. 25.

Two drivers that could not stop going off were Tijmen van der Helm and Julien Andlauer. The JDC-Miller Porsche driver would go off no less than five times, all during the second half of the session. For what it’s worth, teammate Laurin Heinrich also had an off at Turn 8 before handing the No. 5 over to the Dutchman. Likewise, Andlauer would leave the track four times during his stint in the No. 7 during the session.

Meanwhile, GTD PRO caused the only red flag of the session. Neil Verhagen crashed at the final corner in the No. 1 BMW with forty minutes remaining. Like Pfaff, the Paul Miller Racing BMW will lose their fastest lap in qualifying.

Simultaneously, to Bamber in GTP, Alexander Sims waited until the final moments to turn the fastest lap of the session. The British Corvette factory driver clocked the 1.7-mile street circuit at 1:10.109 with six minutes remaining to solidify his top spot in GTD PRO. Tommy Milner turned a 1:10.553 to complete a Corvette Pratt Miller 1-2 in the session. Max Esterson in the Rahal Letterman Lanigan McLaren rounded out the top 3 in class.

With practice complete for the day, the field now turns to Qualifying. GTD PRO qualifying takes place at 4:50pm, followed by GTP starting at 5:10pm.