SILVERSTONE, U.K. -- On the face of it, normal service was resumed during Friday practice at Silverstone.
Two weeks after struggling with cooling issues in Austria, Mercedes returned to the top of the timesheets on Friday with its drivers split by less than a tenth of a second. The faster of the two, Valtteri Bottas, held a two tenths advantage to Ferrari, and over the long runs the gap to the red cars extended significantly to over a second.
But Friday's practice sessions for the British Grand Prix were anything but conclusive.
Gusty conditions, a new track surface and relatively low ambient temperatures meant no one hooked up a perfect lap on low fuel and fresh tyres. Bottas' fastest time was a 1:26.732, but combine the best sectors of both Mercedes drivers (Lewis Hamilton was fastest in sector one and Bottas in sectors two and three) and the theoretical fastest lap time for Mercedes drops to a 1:26.248. So even Bottas' fastest lap had somewhere in the region of 0.5s of theoretical improvement in it and Hamilton's trip across the grass at Becketts and Chapel was a very visible representation of how difficult the conditions were.
"It was really, really tricky and you might have heard Lewis on the radio talking about it," Mercedes technical director James Allison said. "The wind makes for a very snappy rear and also this new asphalt and relatively low ambient temperature means the tyre does not quite get into the window where it really singing, so it makes the car very nervous."
The resurfacing of the track, which was only finished last week, should not be underplayed. Not only is the surface brand new, super smooth and containing a high level of sticky bitumen, it has also changed the very nature of some of the corners. Parts of the track that used to be cambered to the inside to aid cornering are now cambered to the outside and teams and drivers are still getting their heads around how to tackle it.
"The track has been resurfaced but also the bumps and cambers of the corners have changed, which is probably why the drivers need some time to understand the right lines that are different from last year," Pirelli tyre boss Mario Isola said. "Some of the corners are on negative camber, which is pushing you to the outside of the corner."
One result of the car being pushed wide over such a smooth track surface is a high level of abrasion on the tyres on the left-hand side of the car. For Ferrari that was a major issue and manifested itself in dark lines on the surface of the front left as it literally wore away.
"You saw some black lines because the tyres were running on their construction," Isola added. "They were finished!"
The issue was so bad for Ferrari that team principal Mattia Binotto believes it accounted for a lot of the team's lack of lap time to Mercedes. Both Ferraris were faster than Bottas in the first sector but were losing over 0.4s to the Finn in the final sector -- a loss of time Binotto says was related to the increasing wear on the front left.
"We had really high wear on the front tyres -- especially on the front left -- somehow this was really affecting the single qualifying lap because if you look very closely we were strong in the first and second sectors but weak on the last one," he said. "There was understeer, and that understeer is propagating around the lap, and we were damaging them even without high fuel."
Such was the wear issue that a repeat on Sunday would result in a two-stop strategy for a number of teams. Over a long run the issue naturally gets worse and in the battle at the front Ferrari was really hamstrung by the front left.
Over an 11 lap run on the medium tyres on Friday afternoon, Bottas managed an average lap time of 1:31.028 while Leclerc using the same compound over 12 laps could only average a 1:32.629. That level of performance difference is stark and if it is repeated on Sunday would see Mercedes gallop away.
"In the race runs we were struggling a lot with the two front tyres but the front left was particularly dead so we need to work on that," Leclerc said. "I expected Mercedes to be the team to beat this weekend and they confirmed that today that they are the team to beat this weekend, very, very quick during race pace."
But with the opportunity to work on setup ahead of final practice on Saturday, Binotto is confident the issue can be overcome.
"I think we will focus on that this evening. Overnight, we will see what we can do with the front wear. By the time the car will be balanced I think we will get a better judgement of our overall performance in Silverstone."
And that's why it's so difficult to judge the real gap between the top two teams based on Friday's running. The Ferrari's setup is likely to be quite different on Saturday and with it the Italian team could close the gap to Mercedes. But equally if Hamilton or Bottas hook up a truly clean lap then they could quite conceivably combat any gains made by Ferrari.
And to make things even more complicated, Red Bull also failed to show its true potential on Friday. The long-run pace puts them in touch, or perhaps ahead, of Ferrari but Max Verstappen finished seventh in the standings after failing to hook up a single lap.
"Of course with a new tarmac you need to understand the grip levels a bit but it is good," Verstappen said. "It is a bit bumpy in some places so that's a shame but in general there is more grip. All the drivers like that.
"In general it was quite windy so it wasn't easy and clearly we didn't have a good car balance so that makes it even more difficult."
But stripping away Verstappen's scrappy single lap, GPS data suggests Red Bull has the edge over Ferrari in both low- and medium-speed corners, while Ferrari had a very slight edge in high-speed and a big advantage over every other car on the straights. Yet it's Mercedes advantage in all types of corners that stands out above the others and means Bottas and Hamilton remain the drivers to beat ahead of qualifying on Saturday afternoon.