|Russian Grand Prix on the BBC|
|Dates: 28-30 Apr Venue: Sochi Autodrom|
|Coverage: Practice, qualifying on BBC Radio 5 live sports extra. Race live on BBC Radio 5 live. Live text commentary, leaderboard and imagery on BBC Sport website and app.|
Sebastian Vettel led a Ferrari one-two in second practice at the Russian Grand Prix as title rivals Mercedes appeared to struggle for pace.
The four-time champion was 0.263 seconds clear of team-mate Kimi Raikkonen while Mercedes' Valtteri Bottas was 0.670secs off the pace.
Lewis Hamilton, seven points behind Vettel in the championship, was fourth quickest, 0.039secs off his team-mate.
Hamilton had a difficult day and also struggled on his race-simulation run.
But Bottas' form was more encouraging on the long runs, matching Vettel's pace as they practised for the first stint of the race in the final part of the session.
Vettel played down the significance of Ferrari's performance, saying: "On paper this looks like a Mercedes track and I am sure they did not show everything today.
"They did not get their lap together. The gap you see is artificial ... it is a circuit that suits them. They will be strong tomorrow."
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Hamilton appeared to be struggling with his car throughout the day - he aborted his first two attempts at a fast lap, made a series of mistakes and was slower than Bottas in both sessions.
"It has generally been a tricky day," said Hamilton. "The Ferrari is definitely quickest as they have been all year so far and we will work to try to pick up some pace tomorrow."
"If we can get out tyres working properly I think we can be closer and similar. There is no difference to our car compared to the previous races so the gap is still very close between us as it has been in the past."
The Red Bulls of Max Verstappen and Daniel Ricciardo were fifth and sixth but 1.4 seconds off Vettel's pace, and the Dutchman ground to a halt with an engine problem midway through the session.
It was another difficult day for McLaren-Honda. Stoffel Vandoorne suffered an engine problem at the end of the first session which required a change of power-unit.
That has resulted in the Belgian receiving a 15-place grid penalty because he has already used too many of the six constituent parts of the engine. Vandoorne is now on his fifth turbocharger and fifth MGU-H, the part of the hybrid system that recovers energy from the turbo, when only four changes are permitted in the entire 20-round season.
Team-mate Fernando Alonso was 12th quickest, 2.6 seconds slower than Vettel.