George Russell has identified the area that is potentially affecting Mercedes at Silverstone, as they struggle to match the single-lap pace of their rivals.
The Brit could only manage the 12th quickest time in FP2, with his best 1.1 seconds off Max Verstappen.
After the session he admitted that it was not the best session for Mercedes after Lewis Hamilton also finished 15th quickest: "Definitely not our finest Friday, I think conditions will be different tomorrow."
Russell attributes their lack of pace to their performance on the Soft tyre, as they struggled to match rivals Ferrari and Red Bull as customer team Williams produced faster times.
"We need to try and get to the bottom of it because the pace in FP1 was looking reasonably good on the Medium tyre," he added.
"We thought we'd be right up there if we took the Soft tyre, but in FP2 we were nowhere so we need to try and understand that."
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Mercedes affected by hotter temperatures
Russell believes the W14 is sensitive to the high temperature, which in turn affects their ability to extract pace over one lap.
"We're seeing a small trend that when the temperature is hotter, we seem to take a bit of a step backwards," he explained.
A lot of drivers also complained about the windy conditions, which made it tricky for Mercedes to understand the updates they brought to this track.
He added: "It's so windy out there at the moment for all the drivers, everybody's speaking about it. Not a lot to take away from the upgrade as such, but come qualifying I'm sure we'll know where we stand."