German GP: Nico Rosberg says brakes still an issue for Mercedes

Both Rosberg and team-mate Lewis Hamilton changed their brakes under parc ferme rules after qualifying on Saturday, leading some rival teams to consider a protest against Mercedes.

Rosberg suffered several lock-ups in Q1 while Hamilton crashed heavily in the same session when his front-right brake disc failed.

Rosberg won the Hockenheim race from pole position by more than 20 seconds from Williams driver Valtteri Bottas, but said he was still suffering issues with his brakes despite changing the rears for the race.

"Yesterday was very problematic in qualifying with the brakes and still continued today to be difficult," Rosberg said.

"So that's something we need to work on, [but] it's an ongoing process with different solutions.

"Tyre degradation was [also] really on the limit to do two stops.

"The tyres were finished at the end of each stint.

"I had a big battle going on right behind me, with two cars that were actually quicker than me at the time, [and] that didn't look good - they were left, right and centre, locking tyres. That was a bit of a concern."

Rosberg was also pleased to see Mercedes remain dominant in race trim, despite removing its advanced FRIC (front and rear interconnected) suspension system ahead of the weekend, but said his team would need to investigate why Williams appears to have closed the gap in qualifying for recent races.

"It's great to see that without FRIC we are still dominant," Rosberg added.

"In qualifying, we've seen already in Austria Williams beat us.

"We need to look at why they are a bit closer relatively in qualifying - try to understand that, but we're still the dominant force, that's great to see, and we need to keep that going."