Mercedes' Hamilton bemoans lack of grip during Russian GP practice

The world champion, who ended second practice quickest, spun in both sessions as drivers struggled to keep their cars on track.

"The grip is very poor, you are sliding around a lot, struggling with the balance," said Hamilton.

"As always, it's like trying to balance a knife on a tip, which is pretty much impossible and here even more so.

"It's even harder for some reason. I think it's because the track has very low grip and then the tyres on top have low grip in general.

"The tyres aren't very good here. You're just sliding, it's like driving on ice, it's crazy.

"Hopefully it gets warmer, the rubber goes down on this track and it gets better."

Nevertheless, Hamilton said he was fairly happy with his Friday running though was unsure what slot on the front row would prove the most beneficial on Sunday.

"Generally it was a good day," he said. "Our goal is to lock out the front row."

"Pole or second, I don't know which is best because it's such a long run down to Turn 1.

"I'll do the best I can. I feel pole is an opportunity for us this weekend for sure.

"This is a weak circuit for me but I think I've found something so hopefully we'll see the result in that tomorrow."

His team-mate Nico Rosberg added the track surface is very different to any other F1 venue, which makes it tricky for drivers.

"The asphalt is strange here, just different to everywhere else," he said.

"Smooth might be the right word.

"So it's not easy to get it right car-wise or driving-wise.

"It's been an interesting day but good. We got off to a good start."