Mercedes look to be playing catch up after a difficult run in pre-season testing where they completed the fewest laps of any of the 10 teams. Hamilton spun twice and both drivers complained of rear end instability.
Speaking after the conclusion of FP1, Wolff said that the car was more “together” but revealed the team still had work to do.
“It is better together,” he told Sky Sports F1. “It’s not as poisonous at the rear as it was in the test, although it’s not yet in the super sweet spot.
“We have some work to do and see what it does in the colder conditions. But definitely a step forward.”
More will be revealed in FP2, which gets underway and 6pm local time (3pm UK time) on Friday.