There was immediate drama as dawn broke, as Kamui Kobayashi spun the #48 Action Express Cadillac at Turn 1 while attacking Renger van der Zande for the lead a short time after the restart period that followed the eighth full-course caution of the race.
After a comfortable spell out front for the Ganassi car, the ninth yellow came with a little under eight hours to go caused by another spin for the PR1/Mathiasen Motorsports Oreca.
Ganassi took the opportunity to change the nose on the #01 Cadillac DPi-V.R, dropping van der Zande to fifth and allowing the WTR Acura ARX-05 of Helio Castroneves into the lead.
At the restart, van der Zande was on the move, picking off the Cadillacs of Jimmie johnson and Pipo Derani to move into third, and some laps later the Dutchman found a way by the Meyer Shank Racing Acura of Dane Cameron to seize second.
With a little more than seven hours on the clock, van der Zande passed Castroneves to lead, but during the next pitstop phase at the start of Hour 18 the Ganassi car lost ground as van der Zande handed over to ex-Formula 1 driver Kevin Magnussen.
That gave the initiative back to WTR, and when Castroneves handed over to Rossi midway through the hour, the IndyCar ace resumed comfortably in front, leading Magnussen by around three seconds as the 18-hour mark arrived.
Felipe Nasr was third in the best of the AXR Cadillacs, eight seconds down, while Olivier Pla had the MSR Acura in fourth ahead of Simon Pagenaud in the second AXR Cadillac.
LMP2: Game on between Tower and Era
The ninth caution reset the fight in the LMP2 class, with the Tower Motorsport by Starworks Oreca and Era Motorsport Oreca put on the same lap.
Gabriel Aubry in the Tower car was tasked with holding off Era counterpart Kyle Tilley, and the Frenchman was able to build enough of an advantage to hand over to fellow countryman Matthieu Vaxiviere with the lead in tact.
With six hours of the race left, Vaxiviere was just two seconds ahead of Tilley, while the DragonSpeed Oreca was third but a lap down in the hands of Christopher Mies.
Riley Motorsports continued its untroubled run towards victory in the LMP3 division with a slightly reduced margin of four laps over the Sean Creech Motorsports squad.
GTLM: Corvette back in front
Following a brief spell in the lead for BMW, Corvette retook control in the GT Le Mans battle and held a solid one-two with six hours of the race to go.
Prior to the ninth caution, the top three cars all pitted together, and it was at that juncture that the BMW driven by Connor de Phillippi surrendered the advantage to the Corvettes.
The #3 Corvette of Antonio Garcia briefly took the lead, but shortly after the sister C8.R of Tommy Milner got back in front, and after the next round of stops – when Nick Tandy took control of the #4 and Jordan Taylor the #3 – it was the silver Corvette that consolidated the lead.
Tandy led by around five seconds over Taylor with six hours to run, while John Edwards was a further seven seconds back in the best of the BMWs.
Risi Competizione’s Ferrari 488 GTE ran fourth in the hands of Davide Rigon ahead of DTM ace Timo Glock in the second of the Team RLL-run BMW M8 GTEs.
In GT Daytona, a spirited battle between Daniel Serra’s Ferrari and Maro Engel’s Mercedes was finally resolved in favour of the AF Corse Ferrari 488 GT3 shortly before the 18-hour mark.
Andrea Caldarelli had the Paul Miller Racing Lamborghini Huracan GT3 up to third, 30 seconds down, followed by Trent Hindman in the Wright Motorsports Porsche 911 GT3 R and Laurens Vanthoor in the Pfaff Motorsports Porsche.
The SunEnergy1 Racing Mercedes had slipped to sixth, with Mikael Grenier at the helm.