Audi and Toyota shared honours in two rain-affected free practice sessions ahead of this weekend's fifth round of the World Endurance Championship at Austin.
Loic Duval was fastest in the opening session aboard the #2 Audi R18 e-tron quattro on 2m03.749s, which was seventh tenths quicker than Benoit Treluyer in the #1 R18. Both Audis set their times on wet-weather tyres.
Anthony Davidson then set the best time of the day in the Toyota TS030 HYBRID in the second session.
He set a time of 2m00.758s on intermediate Michelins at the start before heavy rain effectively brought the second session to an early end.
Allan McNish was fastest in the #1 Audi when the entire field headed for the pits as the rain intensified.
John Martin was fastest in LMP2 in the best of the G-Drive/Delta-ADR ORECA-Nissan 03 in practice two, while GTE Pro was led by Frederic Makowiecki in the #96 Aston Martin Vantage GTE.