JEREZ, Spain (AP) — Jenson Button steered his repaired McLaren to the fastest lap on Wednesday, and Nico Rosberg helped Mercedes rebound from Lewis Hamilton's crash with the longest run on the second day of Formula One preseason testing.
Otherwise, most teams continued to struggle with their new cars following a massive rulebook overhaul that includes a shift to a turbo engine and more sophisticated energy recovery systems.
Four-time defending world champion Sebastian Vettel only managed eight laps around the Jerez track before Red Bull's engine maker, Renault, reported a malfunction and the team decided to call it quits. That gave Vettel a total of 11 laps to start the preseason.
"Obviously we've not had a lot of running and have a few problems to sort out, but with such big rule changes it is usual to have some teething problems. That's what tests are for, to sort those issues out," said Vettel, who now hands the wheel to new teammate Daniel Ricciardo for the remaining two days in southern Spain.
An electrical problem had kept Button in the garage on Tuesday, but he was the first out on wet tires in the morning and after the asphalt had dried he set the benchmark lap time with 1 minute, 24.165 seconds.
The former world champion is aiming to help McLaren bounce back from its worst season since 1980 after it didn't reach the podium last year.
Rosberg led the eight-car field with 97 laps, a day after a front wing problem sent Hamilton's Mercedes flying into the barrier.
Rosberg said the new Mercedes F1 W05 has little in common with its predecessor and compared its steering wheel to a "smartphone with all the information on it."
After overnight rain, the session's 9 a.m. start was delayed as a tractor worked its way around the track spraying more water on the already damp asphalt so teams could test Pirelli's tires for wet surfaces. But by noon the sun had come out and the track was dry as forecasts of showers never materialized, leaving teams to run under normal conditions.