Jenson Button finished at the top of the times in Turkey today, albeit only just ahead of Nico Rosberg.
As ever the true picture will only emerge in qualifying, but it was a respectable start to the Istanbul weekend for the McLaren driver.
Button made only a brief appearance in the morning’s rain as the team opted to save its wet and intermediate tyres, on the basis that it could rain on Sunday.
“The day was pretty good,” said Button. “I had a quiet morning, lots of tea, didn’t do any running in the first session because it was very wet, and also we didn’t want to use too many sets of wet tyres, because you are limited. This afternoon we did quite a bit of running, which was positive.”
McLaren’s biggest problem is under braking for Turn 12, where all the cars are bouncing on the bumps, but the MP4-26 appears to be struggling more than most.
“My feet are hurting a little bit from Turn 12, on the bumps! I don’t know if you’ve watched the cars there, but wow, it’s bumpy, it’s like they put a motocross jump in, just before the corner.
“Apart from that I’m relatively happy. There’s always things that you want to improve. The car is working reasonably well. I’ve been trying a few things out with the limited running that we have. And I think we’ve made some good progress. There’s a lot of data, but trying to get the car to ride the bumps well into Turn 12 is something that’s been a little bit difficult. But we’re trying our best, and I think we’ve improved a little bit, which is good.”
Button said a lot of thought is going into protecting the tyres, especially through Turn 8.
“We ran both tyres in the session, as I think everyone did. Turn 8 is very difficult for the car, because you can damage fronts, you can damage rears, it’s whatever your balance is. It’s about getting the balance right. We’ve concentrated on that quite a bit today. And the car’s working well.
“We haven’t got everything that we wanted to put on the car here, for certain reasons, which is disappointing. We do have some updates on the car here, which is nice.”
Adam Cooper's F1 Blog 
That first slomo of JB hitting the bumps made me think something was seriously broken, it was jumping like a lowrider.
Strange that Mclaren DNA just seems to include “very stiff front end setup”, this sort of thing has occurred in so many seasons.
It’s like a motocross jump? Looking forward to seeing Petrov approach it then!
The Mclaren’s porpoising was the worst of the field, with the Renault/Lotus looking like there weren’t any bumps at all. Not sure it all had to do with suspension set up. It could be there’s a enough of a difference between the wheelbase of one team to another that makes the likelihood of the car getting into a suspension over-correction cycle. The MP4-26 did indeed look like they had taken the dampers out.