Paffett: Tyres the biggest issue

The Briton set the fifth fastest time as he gave the MP4-25 its maiden run, and found the heavier fuel load and narrower tyres the biggest difference from the 2009 machinery.

"With such narrow front tyres, and the shape of them as well - they're a lot more curved - you do lose a lot of front grip. That's what we've got to try and get back," he told AUTOSPORT. "That's the biggest difference out of all the changes we've had this year.

"You have less front end braking. Because the aero takes over more at high speed, that's not so much of an issue. But certainly at low and medium speed, where you really demand the mechanical grip, is the biggest issue and the biggest thing you've got to try to overcome."

Paffett added that McLaren was pleased with the first day's running.

"We've got to be relatively happy with the day, we've got through it without any problems. The initial feel of the car is good, but you never really know the speed - especially with the regulations this year with the fuel, you don't know what people could be running. Generally, we're happy with today."

Lewis Hamilton will take over the MP4-25 tomorrow.