Cadillac spent 59 minutes leading the second IMSA WeatherTech SportsCar Championship practice session at Road America this afternoon. The last minute, however, was the one that mattered as Stephen Simpson threw the No. 85 JDC-Miller Motorsports ORECA 07-Gibson WEC LMP2 to the top of the standings.

The South African toured the dry 4.0-mile circuit (1m55.057s) a tick faster than the Action Express Racing Cadillac DPi-V.R duo of Joao Barbosa in the No. 5 (+0.104s) and Dane Cameron in the No. 31 (+0.167s).

Mirroring Prototype, which had a new leader after this morning’s session, GT Le Mans and GT Daytona also featured new teams and drivers atop their respective classes. In GTLM, Dirk Muller took command with the No. 66 Ford Chip Ganassi Racing GT (2m03.967s) but was challenged hard by Antonio Garcia in the No. 3 Corvette C7.R (+0.026s) and Bill Auberlen in the No. 25 BMW Team RLL M6 (+0.149s).

The fight for GTD honors was even closer as CORE autosport driver Colin Braun took the No. 54 Porsche 911 GT3 R (2m06.963s) to a precariously small lead over Bryan Sellers in the No. 48 Paul Miller Racing Lamborghini Huracan GT3 (+0.019s). Jorg Bergmeister, whose teammate Patrick Lindsey led the first session, held onto third with the No. 73 Park Place Motorsports Porsche 911 GT3 R (+0.066s).

Performance Tech Motorsports continued its season-long domination of PC as Pato O’Ward (2m00.066s) was almost two seconds faster than the rest of the depleted class.

Despite the long and flowing characteristics of the circuit, lap times were incredible close in Prototype, GTLM and GTD. The blended eight-car field of DPis and WEC P2s were covered by 1.1 seconds; the eight cars in GTLM were spread over 1.0 seconds and GTD saw its top 12 covered by the same margin.

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UP NEXT: FP3, 8:55 a.m. ET