Nico Rosberg says his feeling with the brakes is currently a weakness following the second in-season test of 2014 at the Circuit de Barcelona-Catalunya in Spain.
Rosberg was second quickest behind Lotus's Pastor Maldonado in Montmelo and says the brakes on the Mercedes W05 Hybrid is currently his main weak point.
"[The] programme was brakes, an area where I’m not feeling too comfortable – just working around doing different solutions, a lot of different findings on there," Rosberg told journalists, including F1Zone.net.
"A lot of set-up, engine stuff, but it’s so valuable a day like this. During the race weekend you can never do anything as not one run is the same as the next. On a day like this everything is the same – you can just learn so much.
"Everything [is] important – brakes is the area for me where I’m not 100% happy yet. I’m working on it."
Mercedes trialled an exhaust 'megaphone' in Spain in order to address the concerns about the noise level of the new power units but trackside observers, including F1Zone.net, did not notice any difference. The German driver also believes the trial was unsuccessful.
"Unfortunately it didn’t change anything, so we need to keep pushing – we want to as a team make the sport louder and to keep pushing and to try another solution as this was not the right solution," he said.