Valtteri Bottas says the experiment with the double rear wing on the final day of the in-season test at Silverstone provided his Williams with more downforce to give better grip while cornering - something the Finn says the FW37 is currently lacking to its rivals.

Williams trialled the double rear wing with Bottas in the final few hours of the concluding day of in-season testing, having also run the same wing at the Barcelona in-season test, which under current regulations would be illegal but could become an option in the 2017 regulations revamp.

Bottas says the experiments with varying downforce packages on the Williams - the British team also tested all three versions of its 2016 front wings - is aimed to give the FW37 better grip in corners at varying speeds.

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"In the afternoon there was some interesting aero stuff to simulate some different conditions with the car, different kinds of downforce levels, different corners etcetera, so it was all cool," Bottas said.

"It [double rear wing] adds downforce, and the main thing is trying to fine tune the balance a bit better, and how much we gain with x amount of downforce, especially in cornering conditions.

"That is the weakness we have at the moment - cornering grip. So we are trying to see what it does, if we can make the downforce in the corner a bit better."

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