"Romain Grosjean will run a new Haas chassis on Tuesday's opening day of Formula 1's first in-season test of the year at Barcelona.
The Haas driver made an impressive start to the F1 season with sixth in Australia and fifth in Bahrain but has since struggled with the balance of the American team's VF-16."
"The Frenchman said during the Spanish Grand Prix weekend that the team had identified the problems but did not yet know how to solve them.
With two days of testing at Barcelona on Tuesday and Wednesday, Haas is using the opportunity to run a new chassis for Grosjean in a bid to find solutions.
"We've been struggling since China with something we don't quite yet understand so we're going to change everything for the test," said Grosjean.
"It's been hard for everyone because in terms of work everyone has been doing a great job of looking at the data and finding a solution - making the car on paper better - and we always underline that these are problems that Esteban doesn't have.
"It's quite strange that it's only happening in one car and that's why it's going to be very important for us at testing to change the chassis and put the set up in and see if things get better."
Grosjean said that Haas made changes on Friday night at Circuit de Catalunya, but they weren't as successful as hoped.
"We changed the philosophy of the set-up we'd made for China so this should bring the car back to where it was but actually it didn't happen as much as we wanted," he said.
"We went in a good direction that's why I'm saying that everyone has been working well.
"But under the table there's something that we don't see or understand.
"That's why we want to change the chassis to see if there's something weird in terms of torsion or something that's creating issues.""
"You're so angry that you throw your gloves down, and the worst part is; you have to pick them up again." - Steve Matchett