Colin Braun led the way in the opening practice session of the IMSA WeatherTech Sportscar Championship’s Six Hours of The Glen.

The #60 Meyer Shank Racing Acura ARX-06 turned in a time of 1:33.563 on his ninth lap before the rain came.

Three of the top four fastest cars turned their fastest laps on their seventh lap of the session.

“The car was really good,” Braun said. “Obviously not a tonne of laps but enough to get a feel for it and get a little bit of a balance check.”

The Meyers Shank Acura’s pace-setting form comes following the team’s their test at Watkins Glen on May 26.

Australian Matt Campbell put in the second fastest time of the session. The #7 Porsche Penske Motorsports 963 clocked a 1:34.972 lap around the famed 5.43km circuit.

The #6 Porsche Penske Motorsports entry was third fastest with a time of 1:34.863.

Cadillac Racing, coming off their outstanding third and fourth-place performance at Le Mans, put in the fourth fastest time of the day at 1:35.181.

Under heavy rain, the track went green with 24 minutes remaining in the 90-minute session.

An hour into the session, the #35 TDS Racing Oreca 07 Gibson LMP2 brought out a red flag after contacting a barrier and causing repairs to be made before cars could return to the track.

The #3 Corvette C8.R was a disappointing fifth in the GTD Pro class. The Corvette turned in a lap of 1:47.166 which was only the twelfth fastest time among both GT classes.

Leaders in other classes:

LMP2: #11 TDS Racing Oreca 07 Gibson, 1:36.066

LMP3: #30 JR III Racing Ligier JS P320 VK: 1:41.139

GTD Pro: #62 Risi Competizione Ferrari 296 GT3: 1:46.552

GTD #1 Paul Miller Racing BMW M4 GT3: 1:46.457

Qualifying begins at 02:20 AEST Sunday June 25.