Pirelli happy but keen to analyse 2017 F1 test cars' downforce

The first four of the 24 days testing of next season's wider front and rear rubber have now been completed, with Ferrari using the wet compounds at Fiorano on Monday and Tuesday, and Red Bull the slicks at Mugello on Wednesday and Thursday.

While the tests were blind for both teams, the key for Pirelli is whether the modified 2015 cars are representative of the downforce levels the 2017 designs' wider wings and bigger floors will generate.

"We're happy because finally we've been able to start work on the new wider tyre for next season," Pirelli motorsport chief Paul Hembery told Autosport.

"There is obviously plenty of work to do as we've only started some screening work on different aspects of the tyres. It's just the first step of many towards where we need to get to.

"The big challenge now is trying to get an understanding of the car, and how close it is in terms of downforce compared to what we are going to see next year.

"The teams have obviously been given a set of regulations to allow them to create a car, but it's not set they will be able to achieve the required downforce levels.

"That has a big impact on the way the tyres are performing, so there is going to be a fair bit of analysis of that when we get back, to understand how close we are or how much we are missing compared to next year.

"We need to look at all the data to see where we are first compared to the simulation work we've been working with."

Pirelli now has a few weeks before testing recommences next month; Ferrari is on slicks at Barcelona on September 6-7, with Mercedes also on slicks at Paul Ricard on 6-7-8, followed by a wet test on the same circuit on 21-22.

Hembery added: "The car doesn't look like what it's going to be next year, and that's the point.

"It's a hybrid of a hybrid, and that was done so they wouldn't be able to start working on next year's car.

"The counterpoint to that is we need to be sure we are working with something that is representative, and that's what we are analysing because it is an aspect that is crucial to our work."

Hembery also praised the driver feedback, with Sebastian Vettel and Esteban Gutierrez having been in Ferrari's modified SF15-T on Monday and Tuesday respectively, and Sebastian Buemi driving across both days for Red Bull in an RB11.

"It's been good as they've given us some idea as to what we need to be working on, and where they are expecting us to be," said Hembery.

"We're happy to have physically started work on the new tyre, but it probably won't really come together until people see them next year in February."