Grosjean believes Haas needs to change brake suppliers

The Frenchman has struggled to find a consistent feel with the brakes supplied by Brembo during pre-season testing, with Haas having not fully solved issues it faced in 2016.

The team is planning a test with Carbone Industrie at some point early in the campaign to see if that cures its problems, as work continues on a solution.

But Grosjean, who is particularly sensitive to brake feel, says that he is counting down the days until the change of supplier happens.

"I'm not going into detail, but I don't like it," he said when asked by Motorsport.com about the current brake situation.

"I can't wait to get back to something different."

Pushed on whether he felt Carbone Industrie was the solution, Grosjean replied: "It is the solution. Now, when will it arrive? I don't know."

Steady progress

Grosjean said he was pretty encouraged with the progress that Haas and engine partner Ferrari had made in 2017 – and reckoned the only stand out issue other than brakes was an understeer characteristic.

"Yeah, we are struggling a bit with understeer," he said. "We need to understand why. We've been trying a lot of different set-ups and a lot of different things, assessing what tools do what.

"You don't need a perfect set-up here in winter testing, but we want to be able to know, if we change the rear suspension geometry or the front stiffness, what does it do, and so on."