For the first 15 minutes or so of this hour, the safety car neutralised the race. Both Toyotas came in during that time, with Fernando Alonso handing #8 Toyota over to Kazuki Nakajima and Jose Maria Lopez replacing Kamui Kobayashi in #7 Toyota. Both had to wait for the safety car trains to pass the pitlane exit, meaning the gap increased to around a minute.
Meanwhile, Mikhail Aleshin in the #11 SMP and Sergey Sirotkin in the #17 SMP followed in third and fourth. The #3 Rebellion, now with Thomas Laurent aboard, had slipped to fifth, some 44 seconds behind Sirotkin. This was because the car was delayed in a long stop which saw it boxed in by other cars, but during the stint Laurent was the fastest car on track, setting consistent laps quicker than even the two leading Toyotas.
The SMPs pitted on consecutive laps, handing third place back to Laurent temporarily. Laurent managed to jump Sirotkin in the stops, however, elevating him to fourth, some 30 seconds behind Aleshin while lapping consistently quicker.
The ByKolles had been in the garage since the beginning of the hour with persistent fuel-pump issues, slipping way back down the order. It was the same situation with the #10 DragonSpeed, also in the pits for recurring mechanical problems.
After the safety car for the crashed Corvette came in, the gap between the two Toyotas had come down to 42 seconds. Laurent was also much closer to Aleshin, just two and a bit seconds behind, with Sirotkin a further six seconds back.
Andre Negrao leads for the #36 Signatech Alpine outfit in what is proving to be a hard-fought LMP2 lead battle; the Brazilian is up against Roman Rusinov in the #26 G-Drive Oreca.
As the sixth hour began, Rusinov exited the pits ahead of Negrao, who took over the Signatech Alpine from Pierre Thiriet.
And, just moments after they exited the servicing area, the first Safety Car of the race was triggered, partially due to the #43 RLR Motorsport Oreca, which found itself in the gravel at Tertre Rogue. Driver John Farano looked to be getting out of the car at one stage, but was eventually able to get it underway again, and the time spent under the Safety Car procedure was limited.
The SC did little to alter the battle at the front of LMP2, with Rusinov holding four seconds over Negrao, relative to the six held pre-pause.
However, Pastor Maldonado (#31 DragonSpeed Oreca) managed to pass Ho-Pin Tung, who had only recently taken over the #38 Jackie Chan DC Racing Oreca. The move from the Venezuelan ex-F1 driver raised him up to third in class.
As the first half of the sixth hour came towards its end, Negrao was on the pace, and had closed to within half a second of Rusinov. And, as this battle continued, light rain started to fall in the pits.
The track was soon declared wet, though the cars stayed out.
Shortly after that declaration, and with 35 minutes of the hour in the books, Negrao made a highly committed move on the Mulsanne straight apron, in spite of the defensive efforts from Rusinov, to take the lead of the race.
Rusinov looked less comfortable in the rain, and had already fallen back by over a second when they crossed the line less than two minutes later. However, another twist saw both cars dive into the pits courtesy of another safety car, this time triggered by GT contact at the Porsche curves.
The top two retained their order, and ended up behind the same safety car, separate from the rest of the LMP2 pack. Anthony Davidson (#31 DragonSpeed Oreca) and Ho-Pin Tung in the #38 Oreca, in third and fourth, were in the following train, while Ricky Taylor pitted, dropping back to the next of the three SC trains, falling from fifth in the process.
Filipe Albuquerque (#22 United Autosports Ligier) inherited the last of the top five places as a result.
We returned to green flag action with five minutes of the sixth hour left to run, and the LMP2 lead battle were line astern in the train. However, Rusinov seemed unable to challenge, immediately losing time and struggling in the continuing light rain.
As the first quarter of the race came to an end, the gap between Negrao and Rusinov in the LMP2 lead battle was within two seconds.
The GTE Pro battle heated up during the sixth hour, with an 11-car battle taking place before the second safety car split the field.
The ongoing four-car battle continued as driver changes and safety cars created a lot of interest in the race. The battle between the #92 Porsche of Kevin Estre leading the #51 AF Corse Ferrari of Daniel Serra, #63 Corvette of Antonio Garcia and #93 Porsche of Nick Tandy continued.
There was luck for the fight at the front of GTE Pro, as all four contenders were under the same safety car that was out early in the hour for the beached LMP2 car.
Additionally, the safety car brought the top 11 cars in GTE Pro to within 15 seconds of each other.
As soon as the safety car pulled in, Serra took the lead of the class into Indianapolis with Vanthoor trying to get the position back into the Porsche Curves, but was unable to return the favour. There was also a fight for third, with Bamber taking third from Rockenfeller.
The fight between the Ferrari and Porsche continued with clever race craft between Serra and Vanthoor being used to draft and take speed off the other down the straight in a thrilling fight.
The fights continued down the entire top 11 with ding-dong battles, often three-car battles. The losers of the safety cars were the BMWs and Aston Martins, which lost a lot of time by being stuck behind a different safety car, further damaging their race.
Soon, however, the relative pace of the groups emerged, with the top six pulling 10 seconds clear of the rest.
Then came the first major incident of the race, as the #64 Corvette with Marcel Fassler behind the wheel came in contact with the #88 GTE Am Porsche, sending the Corvette heavily into the wall at the Porsche curves, taking heavy damage on both ends.
Naturally, the safety car was called and unlike the first safety car, the field was split behind two safety cars, with the first five cars being separated from the rest of the field.
Despite the excitement and a round of pitstops, the order of in the GTE Pro field remained stable, with the leaders electing to concentrate on the long game, rather than jostling for position at this stage of the race.
Interestingly, only Serra in the #51 AF Corse Ferrari stayed in the car for the whole hour, with the others changing drivers.
The #85 Keating Ford continued to lead the GTE Am battle during the sixth hour, leading Jeff Segal in the #84 JMW Ferrari and Jorg Bergmeister in the #56 Project 1 Porsche.
The battle for the lead in GTE Am was separated in the Safety Car, with the #85 Keating Ford taking a different safety car than the #77 Dempsey Proton Porsche. That put an 80-second gap between the two. After the second safety car of the hour, they would end up fifth in class
While the #85 Ford had a solid lead, the rest were covered by just a few seconds, offering a great fight for the podium.
While the other classes offered a lot of action, the GTE Am field was relatively stable, with minor contact with the #83 Kessel Racing Ferrari and an LMP2 machine, but both cars were able to continue without issue.
There was further issue with the #88 Porsche car with Satoshi Hoshino behind the wheel. He was in a gaggle of traffic when the #64 Corvette came to lap them, making contact, sending them both into the wall. While the #88 Porsche was able to continue, it ended the race for the Corvette and continued a race to forget for Hoshino.
The #60 Kessel Racing Ferrari of Sergio Pianezolla spun at Indianapolis, bringing out a slow zone, but no great damage occurred.