Haas' Romain Grosjean has revealed the team are still not "100 per cent" happy with the brakes on their VF-17.
The Frenchman was only able to clock up 56 laps on Day Three of the first winter test in Barcelona and said there a number of issues to resolve.
“Right now we are not 100 per cent happy with the braking still,” Grosjean said. “But we are going to work around and hopefully find some solutions early in the year.”
“There were a few things that held us back in the garage so we need to work and get better in the future
“But I got the first few laps in the car and learned to drive it a little bit.”
Grosjean also said that the new aerodynamic regulations this year could help breathe new life into some of the circuits on the calendar.
“I think the last generation of cars were not very fun to drive, and now we are back to Formula 1,” Grosjean added.
“It feels pretty good. High speed [corners] are going to be interesting this year, much more than it was in the past. I think some of the circuits are going to be more exciting. I'm looking forward to doing more.”