The #66 Ford GT driven by Dirk Muller turned a 50.924sec lap of the super-fast seven-turn 1.5-mile Lime Rock Park to go a mere 0.097sec faster than Nick Tandy’s best in the #911 Porsche 911 RSR.

Both the Porsches suffered minor off course excursions at Big Bend in the course of the session, but Earl Bamber’s fastest time in the #912 was still good enough for fourth, around quarter second off top spot but less than a tenth slower than the second Ford of Ryan Briscoe.

Jesse Krohn and Connor De Phillippi set the best times in the BMW M8s, 0.36 and 0.56 respectively off Muller’s Ford, while the two Corvettes were almost 0.8sec slower.

In GTD, Kyle Marcelli put the 3GT Racing Lexus RC F on top, just a couple of hundredths ahead of Alvaro Parente’s #86 Acura NSX, which Meyer Shank Racing has confirmed will run for the remainder of the season, as Parente’s co-driver Katherine Legge is a prime title contender.

Andy Lally slotted Magnus Racing’s Audi R8 into third place, ahead of the Turner Motorsports BMW M6, this weekend driven by Bill Auberlen and Robby Foley.

Paul Miller Racing’s Lamborghini Huracan had a small fire on pitlane due to unburnt fuel catching light in the exhausts, but not before Bryan Sellers had set fifth fastest time, while Lawson Aschenbach wheeled the second MSR Acura to sixth.

Lime Rock, IMSA first practice 

Pos.	#	Driver	Class	Chassis	Time	Gap
1	66	Joey Hand    Dirk Müller	GTLM	Ford GT	50.924
2	911	Nick Tandy    Patrick Pilet	GTLM	Porsche 911 RSR	51.021	0.097
3	67	Ryan Briscoe    Richard Westbrook	GTLM	Ford GT	51.080	0.156
4	912	Earl Bamber    Laurens Vanthoor	GTLM	Porsche 911 RSR	51.166	0.242
5	24	John Edwards    Jesse Krohn	GTLM	BMW M8 GTE	51.286	0.362
6	25	Connor de Phillippi    Alexander Sims	GTLM	BMW M8 GTE	51.490	0.566
7	3	Jan Magnussen    Antonio Garcia	GTLM	Corvette C7.R	51.708	0.784
8	4	Oliver Gavin    Tommy Milner	GTLM	Corvette C7.R	51.723	0.799
9	14	Kyle Marcelli    Dominik Baumann	GTD	Lexus RC F GT3	52.303	1.379
10	86	Alvaro Parente    Katherine Legge	GTD	Acura NSX GT3	52.308	1.384
11	44	Andy Lally    John Potter	GTD	Audi R8 LMS GT3	52.338	1.414
12	96	Bill Auberlen    Robby Foley	GTD	BMW M6 GT3	52.506	1.582
13	48	Bryan Sellers    Madison Snow	GTD	Lamborghini Huracan GT3	52.509	1.585
14	93	Justin Marks    Lawson Aschenbach	GTD	Acura NSX GT3	52.511	1.587
15	63	Cooper MacNeil    Gunnar Jeannette	GTD	Ferrari 488 GT3	52.567	1.643
16	58	Patrick Long    Christina Nielsen	GTD	Porsche 911 GT3 R	52.569	1.645
17	33	Jeroen Bleekemolen   Ben Keating	GTD	Mercedes-AMG GT3	52.592	1.668
18	15	Jack Hawksworth    Mario Farnbacher	GTD	Lexus RC F GT3	52.633	1.709