Mercedes also ran well, with Nico Rosberg completing 97 laps, but it was a session to forget for world champion Sebastian Vettel as his new Red Bull RB10 managed just eight laps of the Spanish circuit before technical problems set in.
After overnight rain had left the circuit damp, Pirelli decided to bring forward Friday’s wet-weather tyre test and sent trucks onto the track before the start of the session to artificially water the surface and make sure it was sufficiently wet.
Button was one of the first drivers out on track in the MP4-29, doing installation runs as well as testing the new treaded rubber. By the end of the morning the Briton had recorded the fastest time, but he went quicker still in the dry afternoon session, recording a best lap of 1m 24.165s. More importantly, the McLaren driver logged 43 laps in his new car - a decent count when compared to many of their rivals.
“For our first day of actual running, we were able to get a good understanding of the car, and the way the engine and turbo behaves,” said Button. “It’s tricky, and very different to what we’re used to, but I could feel that these cars will be enjoyable to drive.
“Of course, it’s still early days, and there’s a lot of work ahead of us. We need to work on both braking and traction; but that excites me, because there’s a lot of potential to adjust those parameters. The new braking system is very complicated, and getting it right will be tough. But these are all things we can work on: there’s nothing about the car that unsettles me, and there’s plenty of scope to explore the set-up. It will just take time.”
After a difficult first day in Spain, Red Bull struggled again on Wednesday, completing just a handful of laps before power unit supplier Renault reported an energy store issue on the RB10. With two days of running remaining, the team opted to end their day early in order to fully investigate the problem.
“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,” said Vettel, who will hand the car over to Daniel Ricciardo for the remainder of the Jerez test.
“That's what tests are for, to sort those issues out. The next two days will be important to get some track time to prepare for the tests in Bahrain.”
Renault’s other runners were similarly afflicted by problems. Caterham’s Marcus Ericsson completed just 11 laps, whilst Toro Rosso didn’t even manage to get their STR9 out of the garage after electrical problems.
Things were much better for the Ferrari and Mercedes-powered cars. Having topped the times on Tuesday, Kimi Raikkonen was again impressive in the Ferrari, logging the second-fastest time as well as 47 more laps. He was followed on the timesheets by Williams’ Valtteri Bottas and Mercedes’ Nico Rosberg. Both impressed, but Rosberg’s ability to do long runs between pit stops in the F1 W05 meant that Mercedes finished the day in arguably the best shape of any team.
“That was a great team effort today,” Rosberg enthused. “We had to fix a problem on our car overnight. The guys worked through the night back at the factories and flew in the parts just in time this morning, so we were able to do a lot of mileage today which is great for our learning process.
“It was a great feeling to put some good miles on the new Silver Arrow and there's a lot of new stuff to clear because it's very different to the old car. It's heavier, you have less downforce and the steering wheel is completely different; it's almost like a smartphone with all the information on it!
“Every lap is important to get used to the new systems and it helped a lot that I have worked on this already in the simulator. We don't know yet where we are compared to the other teams, but we can be quite happy after the first two days of testing here in Spain. Now I look forward to getting back in the car on Friday.”
Sergio Perez set the fifth best time, though the Mexican brought out the second red flag of the day when his Force India VJM07 came to a smoking halt at Turn 1. The first track caution had been caused by countryman Esteban Gutierrez who spun his Sauber C33 into the Turn 5 gravel on his way to sixth on the timesheets.
Despite the off, Sauber were pleased with their day’s work.
“Today we continued assessing reliability and performed a number of functions checks,” said Sauber’s head of track engineering Giampaolo Dall’Ara. “At this stage of the development progress follows a steep curve and, while we keep working hard, we are rather pleased with our achievements.”
Testing continues at Jerez on Thursday, when Marussia are expected to debut their new Ferrari-powered MR03 machine.
Unofficial Wednesday test times from Jerez:
1. Jenson Button, McLaren, 1m 24.165s, 43 laps
2. Kimi Raikkonen, Ferrari, 1m 24.812s, 47 laps
3. Valtteri Bottas, Williams, 1m 25.344s, 35 laps
4. Nico Rosberg, Mercedes, 1m 25.588s, 97 laps
5. Sergio Perez, Force India, 1m 28.376s, 37 laps
6. Esteban Gutierrez, Sauber, 1m 33.270s, 53 laps
7. Marcus Ericsson, Caterham, 1m 37.975s, 11 laps
8. Sebastian Vettel, Red Bull, 1m 38.320s, 8 laps