Ferrari's on-form Felipe Massa set the pace in Belgian Grand Prix free practice on Friday while world champion team mate Kimi Raikkonen again looked out of sorts.
Brazilian Massa, six points behind McLaren's Lewis Hamilton in the championship after winning in Valencia last month, dominated a chilly and overcast morning session with a lap of one minute 47.284 seconds.
He was then second in the afternoon, just 0.050 slower than Renault's former champion Fernando Alonso's quickest lap of 1:48.454.
Raikkonen, winner of the last three races in Belgium but without a victory since the end of April, was second quickest in the morning in 1:47.623 but spun off into the barriers after lunch when a light drizzle descended.
The Finn nursed his stricken car back to the pits without the broken rear wing that had fallen off in the middle of the track.
Italian Giancarlo Fisichella also crashed his Force India and the session was then stopped for 10 minutes while marshals scrubbed fluid off the circuit.
"I clipped the kerb and the surface was a bit slippery there because of the rain," said Raikkonen. "I ended up spinning and then hitting the barrier.
"Unfortunately not only did the rear wing break, but the floor was also damaged and it could not be repaired in time...let's hope tomorrow morning there's no rain so that I can run more consistently in the dry."
NIGHTMARE START
The daunting high-speed track is Raikkonen's favourite but he needs to beat Massa this weekend to get back into the reckoning and prevent Ferrari from putting all their weight behind the Brazilian's title challenge.
Hamilton, the 23-year-old Briton who is 13 points clear of Raikkonen with six races remaining, was third in the morning ahead of Finnish team mate Heikki Kovalainen. The two reversed their positions in the second session.
"We're just as competitive as them. We're pretty much equal with them," said Hamilton of the Ferraris. "They have a bit more speed at the end of the straight, but it's only by a couple of kph, not five or eight.
"I don't think it will make any difference."
Germany's Adrian Sutil, whose Ferrari-powered Force India team have yet to score a point, was a surprising eighth fastest with a quick lap right at the end of the afternoon before the skies opened.
Honda made a nightmare start to their weekend in the Ardennes forests, with Jenson Button and Rubens Barrichello occupying the last two slots on the timesheets and more than three seconds off the pace.
Australian Mark Webber was a casualty of a shower midway through the second session, his Red Bull sliding off into the barriers at Rivage, while Renault's Nelson Piquet also lost his rear wing.