Helio Castroneves had contact with Felipe Nasr midway through the 16th hour of the Rolex 24, sending the No. 7 Acura Team Penske ARX-05 to the garage and leaving the No. 5 Mustang Sampling Cadillac of Joao Barbosa on a lap of its own.

Castroneves was running second at the time – a lap ahead of third-place Nasr in the No 31 Whelen Engineering Cadillac. The Penske team changed the left-side intercooler, radiator and bodywork. The end of the hour found Castroneves still in the garage running 10th, now 16 laps down.

• Standings after 16 hours

Nasr was second at the end of the hour, one lap down. Third was Bruno Senna in the No. 32 United Autosports Ligier, four laps down. He was followed by Loic Duval in the No. 54 CORE autosport ORECA, six laps down, and Renger van der Zande in the No. 10 Cadillac, seven laps down.

Chip Ganassi Ford GTs ran 1-2 for yet another hour. Richard Westbrook passed his teammate and held point most of the time in the No. 67, before being passed by Sebastien Bourdais in the No. 66.

The third caution waved early in the hour for light contact involving the No. 73 Park Place Porsche 911 GT3 R, with Jorg Bergmeister managing to continue. Many contending teams took advantage of the first pace car period in more than five hours to change brakes.

The GTD battle continues to heat up, with six cars on the lead lap. Franck Perera led at the caution in the No. 11 Grasser Racing Team Lamborghini Huracan GT3, but the team was assessed two drive-through penalties for a fire extinguisher infraction and leaving the pit with a hose attached. That dropped Perera to sixth.

Paul Dalla Lana led two laps in the No. 51 Spirit of Racing Ferrari 488 GT3 before being passed by Andrea Caldarelli in the No. 48 Paul Miller Racing Lamborghini.
At the end of the hour, Caldarelli led Alvaro Parente in the No. 86 Acura by 9.053 seconds.
Running seventh in GTD, one lap down, was five-time Rolex 24 class winner Andy Lally in the No. 44 Magnus Racing Audi R8 LMS GT3.

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