Jenson Button has said that the changes that McLaren have made to their car over the last few Formula 1 grands prix are "not working".
The 2009 world champion suffered a mechanical problem in first practice at the Brazilian Grand Prix earlier today, and was almost two seconds off the pace in P2.
The 34-year-old told Sky Sports News: "We've got some things that we're trying out on the car that's been different for quite a few races, and it's not working.
"It's good to know, I feel that it's wrong in many different ways so at least we know the way to go with the set-up, which is positive. The only thing we find quite strange is our straightline speed is so far off. We're not running that different in downforce. We'd struggle to go that speed in a straight line, we'd have to take the wings off.
"I don't know why we're not very quick in a straight line around here and it's something we need to solve because it's a lot of time we're losing on the straights. So a lot of work to do overnight but I think we understand what the issues are and we can solve them for tomorrow."
Button is currently seventh in the drivers' standings, but has finished on the podium just once so far this season.
