Brazilian GP: F1 drivers blame kerbs for slower Interlagos times

The kerbs on the apexes of Turns 2/3 (Senna S), 4/5 (Descida do Lago), 8 and 10 (Bico de Pato) now possess 50mm high bevelled elements.

This has been cited as the reason for slower laptimes in practice this year, with Nico Rosberg's Friday best of 1m12.385s a quarter of a second slower than the 2014 pace. Practice one had been eight tenths slower.

"They've changed the kerbs a lot so now we can't attack the kerbs and have to drive round them. That costs a lot of laptime," said Rosberg.

Asked why times were slower, Lewis Hamilton replied: "I'm pretty certain it's just the kerbs.

"Turn 2 is a big, big kerb. It used to be pretty much flat through Turn 2, but now you have to lift.

"Also Turn 8 has a big kerb. You used to just run over the whole of it. Now you can't. I think those two corners on their own make a big difference."

Force India's Nico Hulkenberg was particularly critical, adding: "I'm not a fan of them, to be honest. I much preferred the old kerbs.

"It was nice to ride them, it looked cool and was fun.

"Now they're so steep and harsh that you can't really ride them. From a driver's point of view it's a step backwards."

Romain Grosjean said the changes had a significant impact on the lines drivers could take.

"The corners are now tighter, not trickier because when you run on the kerb it's very bumpy," he said.

"Most of the time if the car balance is good, it's fine, but it can upset the car.

"So right now we have to avoid them and the car stays more consistent, but there's more corner."

TRACK SURFACE 'CRUMBLING'

There have also been concerns about the quality of the track surface, which was resurfaced ahead of last year's race, with some drivers blaming the World Endurance Championship race that took place three weeks after the 2014 GP.

"The sportscars broke up the asphalt," said Rosberg.

"It's really crumbling in some corners and when you go through those patches you lose a lot of grip.

"We had to be quite creative in trying to avoid those patches with different lines."

Pirelli motorsport director Paul Hembery said the tyre firm would investigate the complaints.

"It's been suggested the last WEC race caused a few problems on the track," he said.

"I haven't seen them myself, but the guys who did the track walk did point it out and I hear some drivers have picked up on it.

"That's something we'll analyse tonight and if there is a concern, we'll take it up with the FIA."