Belgian GP: Mercedes' Nico Rosberg tops practice before tyre blows

Rosberg, who led the way in first practice, clocked a time of 1m49.687s, 0.302 seconds faster than Hamilton on the soft tyres with Red Bull's Daniel Ricciardo four tenths further back.

Rosberg set the early pace on the medium tyres and maintained that advantage when he bolted on the softs for his qualifying-simulation before turning his attention to long-run data gathering.

However, with a little under 30 minutes to go, Rosberg's rear-tyre exploded, sending the German into a spin approaching Blanchimont. He managed to keep the car out of the tyre wall.

Replays seemed to suggest a blister eventually started to fray and eventually resulted in the tyre shredding off the wheel.

Rosberg climbed out of the car unscathed, but the red flag was brought out while marshals cleared away the stricken Mercedes.

The session restarted 10 minutes later, but the red flag was called into action again shortly after the restart when Marcus Ericsson ran wide on the exit of Pouhon, which snapped the car into oversteer and into the barrier.

"I'm OK," said Ericsson, who finished eighth fastest, on team radio. "I hit the wall hard, I'm sorry guys."

Unusually beautiful conditions continued at Spa for second practice, with the air and track temperature 23C and 39C respectively and only a breath of wind in the air.

Red Bull proved to be Mercedes' closest challengers with Ricciardo third quickest, 0.751s off the pace, and team-mate Daniil Kvyat three tenths further adrift.

Ferrari's Kimi Raikkonen, who traditionally runs well at Spa, was fifth quickest ahead of Nico Hulkenberg in the Force India.

After missing first practice as Jolyon Palmer was in the Lotus, Romain Grosjean was seventh ahead of the Sauber duo of Ericsson and Felipe Nasr, who are running the 2015-spec Ferrari engine for the first time this season.

Ferrari driver Sebastian Vettel completed the top 10, ahead of Force India's Sergio Perez.

Carlos Sainz Jr pipped Toro Rosso team-mate Max Verstappen to 12th.

Williams, which typically does not show its true pace on a Friday, finished down the pecking order with Valtteri Bottas and Felipe Massa 14th and 16th respectively.

They were split by Pastor Maldonado, whose Lotus team did an impressive job to fix his car after his first practice crash and get him out for the final hour of the session.

McLaren's Jenson Button and Fernando Alonso, who will start from the back of the field on Sunday after taking big engine penalties, were 17th and 18th with the Manors propping up the timesheets.

PRACTICE TWO TIMES: