SILVERSTONE, England -- Red Bull drivers Mark Webber and Sebastian Vettel posted the fastest times in Friday's practices for Formula One's British Grand Prix, as McLaren's upgrades failed to produce instant signs of improvement.
Having produced a Red Bull one-two at Silverstone last year, Vettel and Webber again go into Saturday's qualifying as the sharpest team.
Webber set the fastest lap of the day in the afternoon session, completing the modified circuit in 1 minute, 31.234 seconds; Vettel set the pace in the morning session by clocking 1:32.280.
Following his spectacular accident in the European Grand Prix two weeks ago, Webber is using a chassis formerly used by Vettel.
The priority for the McLaren team of Hamilton and Button on Friday had been to analyze the performance of its new exhaust blown diffuser, which aids downforce and increases grip -- a device that has worked so well for Red Bull.
The parts arrived at McLaren's Silverstone garage in the early morning -- and are yet to deliver.
"It's a new package and we've got to do a lot of learning," McLaren team principal Martin Whitmarsh said. "I think we got a lot of useful information, now we have to use that information in a way to make the car quicker tomorrow."
The fastest time Button posted was 1:33.2 in the morning 90-minute session -- more than a second behind Vettel.
Hamilton was only a third of a second off the pace with the second-fastest morning time, but the 2008 world champion was more than 1.5 seconds behind Webber later in the day.
"I was actually surprised about the pace of the car this morning," Hamilton said. "The changes that we made to the car, setup-wise, actually didn't make it better. Sometimes you find that's the case. So what we will do is go back to the setup we had earlier on."