BARCELONA, Spain -- Lewis Hamilton says driving Circuit de Catalunya's Turn 9 in the current generation of Formula One car is like being a kid in a roller coaster, but still has concerns about overtaking.

Hamilton has now completed three half days at the wheel of the new Mercedes W08 and on Tuesday set a series of fast times on softer compound tyres. In previous years Turn 9 at Barcelona had required a lift off the throttle, but this year Hamilton was able to take it flat out.

"I think mostly it's the downforce you feel," he said. "It's not more power or anything like that, in actual fact we are slower on the straights, but it's the speed in the corners, it's how late and deep you can brake into the corners. It's how quick you can get back to the gas. How you are able to take the corners flat out pretty easily. It's quite unreal to be honest.

"It's amazing. I'm coming through some of these corners, Turn 9, and I'm coming out of it and I'm like a kid on a rollercoaster ride because it's so much better than it was before.

"They definitely aren't more forgiving, I think they're more peaky. Because we're going faster through the corners, the snap of oversteer happens quicker, so it's definitely harder to catch. Overall it is a harder car to drive but to catch oversteer moments it is definitely a lot harder, which I like.

"However, following is not good. Following is not easy, it's worse to follow another car, which was to be expected. I don't know how that's going to play out in an actual race when there's lots of cars. Just following a couple of cars it was quite a bit worse."

Hamilton's concerns about overtaking have been well documented and he said his on track experiences this week had done nothing to allay his fears.

"When the proposal for the design [of the new cars] came out, the engineers said 'this is the wrong design, this is the wrong way'. Some teams, at least my engineers said that it would make the cars faster, it's going to give us more downforce, but it's going to be harder to follow because there's more turbulence, there's more strong and powerful vortices coming out of the cars, which are ultimately the things that affect the car behind.

"But obviously they're not necessarily listened to and now we've got these cars which look fantastic I think and they drive amazingly well, but just as you get behind another car, you imagine the car in front has 100 per cent pure air in front, and then the car behind has at least half or less than that. So the car behind is getting all the different dirty air that is moving in different ways.

"The car feels one way for a second and then you get a crosswind or something that you're not expecting or you lose front-end grip because the wing stops getting force on the car or the rear does for example. It makes you then have to lift, and you never get close enough. I was behind several different cars and it was not so easy."