The fresh trouble hiding Mercedes' true pace

If the first three grands prix of 2017 have taught us anything, it's that Ferrari and Mercedes are very closely matched, and the smallest details in driving, set-up and strategy can make all the difference to which of these Formula 1 powerhouses comes out on top at any given event.

Ferrari has arguably had the best car in race trim across each of the first three races, on differing track layouts. It was fast on the bumpy streets of Albert Park, on the more conventional sweeps of front-limited Shanghai, and on the rough, hot asphalt of Sakhir's desert setting.

Mercedes has been clearly faster in qualifying, but hasn't easily carried that pace through a grand prix distance. Even Lewis Hamilton's relatively comfortable victory in China was achieved with the help of the Ferraris being buried in the pack early on.

Theoretically speaking, Sochi should be a Mercedes stronghold. The Russian Grand Prix's relatively short history tells us Mercedes is normally imperious around a circuit where having the most powerful and efficient engine really counts on those long, flat-out sections, and on an ultra-smooth track surface that allows F1 cars to be driven faster for longer than is common in the Pirelli tyre era.

Even when Nico Rosberg and Hamilton suffered unexpected setbacks, such as the huge lock-up that forced Rosberg into the pits at the end of lap one of the 2014 race, or the MGU-H failure that prevented Hamilton taking part in Q3 last season, both recovered easily to second place behind their victorious team-mate.

Mercedes has won every F1 race at Sochi held so far comfortably. Although the early races of 2017 increasingly suggest prior form counts for very little, Mercedes should still ordinarily have reason to feel confident coming here.

The chief weakness in the W08 that has allowed Ferrari to win two races despite starting ahead is a propensity for chewing up rear Pirelli super-soft and ultra-soft tyres a little too greedily.

Theoretically, the smooth Sochi asphalt should help negate that weakness and leave the Mercedes drivers free to push the tyres hard without fear of destroying them.

That, coupled with lessons learned from the post-race Bahrain test, where even Hamilton was motivated to do a job he usually hates, should put Mercedes in a much stronger position here.

"We have lots of different elements that affect the rear tyre, like engine braking, different brake biases, different mechanical balances that we run, along with the aero balance," said Hamilton before Friday practice in Russia.

"It's kind of impossible to say it's one thing, but it's a combination of things and it's not necessarily that the combination is wrong - it could be one thing that's not perfectly set that affected it all.

"We will get on top of it very soon, hopefully this weekend. It is an easier circuit for the tyres, more space for the tyres to cool down and it's not really that hot. The track's in its high-30s, and the breeze is quite cool. I don't think overheating's going to be an issue this weekend."

But it looks as though Mercedes is encountering new difficulties getting the Pirelli tyres to work properly at Sochi.

Both Hamilton and new team-mate Valtteri Bottas, a driver with a strong personal record at this track from his Williams days, had difficulty extracting decent grip from the ultra-soft compound. They ended up more than six tenths of a second off the pace set by Sebastian Vettel's Ferrari in Friday practice.

PURE PACE RANKING
1. Ferrari (Vettel) 1m34.120s
2. Mercedes (Bottas) 1m34.790s
3. Red Bull (Verstappen) 1m35.540s
4. Williams (Massa) 1m36.261s
5. Renault (Hulkenberg) 1m36.329s
6. Haas (Magnussen) 1m36.506s
7. Force India (Perez) 1m36.600s
8. McLaren (Alonso) 1m36.765s
9. Toro Rosso (Sainz) 1m37.083s
10. Sauber (Wehrlein) 1m37.441s

"These tyres are very tricky, quite peaky, sometimes they are working and sometimes they are not, which is very strange, so it's hard to keep them operating," explained Hamilton, who endured a messy second session that included almost rear-ending a Sauber.

"Sometimes they are dropping outside the window and Ferrari are keeping them in the window. That's our challenge at the moment."

Both Hamilton and Bottas could potentially have gone a tenth quicker had they each put their best sectors together, but both of them also did more laps during the qualifying simulations than the Ferrari drivers. Bottas, in particular, was urged by Mercedes to try varying his technique to extract more from the rubber.

"If we want to be on the front row, we definitely need to do a better job than we did today with the ultra-soft," said Bottas. "We struggled a little bit with the temperatures [being too low], which normally has been a little bit opposite for us.

"We definitely didn't get the ultra-soft in the correct window for one lap. Ferrari managed to do it today and the difference is big. It only needs a few hundredths at every corner and the difference is that big.

"Our longer runs were definitely better, which is good because Sunday is what matters. But still we want to be in a good place to start the race. It will be a busy evening to look at everything. Getting more out of the tyres will be the main topic tonight."

Bottas's pace over a long run justifies his confidence, as he tops the long-run rankings ahead of Vettel.

LONG RUN RANKINGS (ultra-soft)
1. Mercedes (Bottas) 1m38.709s (15 laps)
2. Ferrari (Vettel) 1m38.885s (10 laps)
3. Williams (Massa) 1m39.799s (12 laps)
4. Force India (Perez) 1m40.381s (9 laps)
5. Toro Rosso (Sainz) 1m40.740s (19 laps)
6. Red Bull (Ricciardo) 1m40.855s (6 laps)
7. Renault (Hulkenberg) 1m40.900s (14 laps)
8. Haas (Magnussen) 1m41.058s (11 laps)
9. McLaren (Alonso) 1m41.203s (8 laps)
10. Sauber (Ericsson) 1m41.447s (11 laps)

LONG RUN RANKINGS (super-soft)
1. Ferrari (Vettel) 1m37.662s (3 laps)
2. Mercedes (Hamilton) 1m38.703s (7 laps)
3. Williams (Massa) 1m38.751s (5 laps)
4. Renault (Hulkenberg) 1m39.553s (3 laps)
5. Force India (Perez) 1m39.664s (10 laps)
6. Red Bull (Ricciardo) 1m39.972s (3 laps)
7. Toro Rosso (Kvyat) 1m41.146s (14 laps)
8. Haas (Grosjean) 1m41.249s (5 laps)
9. Sauber (Wehrlein) 1m41.515s (7 laps)

*McLaren completed no meaningful long runs on the super-soft

Kimi Raikkonen, who was two tenths behind Vettel on pure pace, ran out of sync with the other top cars, so his four-lap long run on ultra-softs at the end of the session is discounted. He was actually fastest of all on that tyre, but when the fuel load was much lighter than it was for his rivals.

Raikkonen also spoiled his earlier super-soft long run with a heavy lock-up that flatspotted the fronts, so his representative race pace on that tyre is also unknown.

As is Hamilton's. He pitted after a handful of laps on the ultra-soft, complaining the car just didn't feel right and saying he couldn't explain why, and his struggles seemed to continue on the super-soft.

Renault's Nico Hulkenberg suggested this year's car are trickier to drive at this track than the previous generation's, saying they are "a lot more on the edge and it's easier to overdo it and go off a little bit". Renault was comparatively weak on the ultra-soft, but much stronger on the super-soft.

Red Bull was deeply underwhelming on both tyre compounds on the longer runs, Daniel Ricciardo (the only Red Bull driver to do anything after Max Verstappen's car ground to a halt with a fuel pressure problem) saying the car lacked consistency from one run to the next. Pascal Wehrlein complained about a similar problem for Sauber.

That suggests Mercedes is not the only team struggling to get the Pirelli tyres to work properly at the moment.

Bottas's long run improved as he went along, but if you scale it back to a like-for-like 10-lap comparison with Vettel's, which should represent a better approximation for similar fuel loads, there is absolutely nothing to separate the two quickest cars.

This lends some credence to Vettel's suggestion that his overall advantage over Mercedes is "artificial".

"I think they will be fine," said Vettel, who "found the car again" in second practice after a "rough start" in the morning session. "This looks like a Mercedes track. Last year people expected Williams to be fastest after Friday, if I remember right, and it turned out Mercedes was the fastest.

"That's how sometimes you can be misled and there's a lot of things we can play within the car: fuel loads, engine modes... On this track there's a lot of things that you can show or not show.

"They didn't show everything today and they didn't get a lap together, so the gap you see, it's artificial."

But that's only true if Mercedes can get the ultra-soft Pirelli tyres working correctly. The Mercedes doesn't look quite as driveable off the slower corners as the Ferrari, and sounds as though it is harsher on the rear tyres under acceleration.

But Sochi's low-abrasion surface will mitigate against the usual penalty for that. Mercedes' problem here seems similar to the one it suffered in Singapore in 2015, when it couldn't get the super-soft Pirellis up into the correct working temperature range. The car was balanced reasonably well, but just lacked grip.

The Pirelli tyres are different now of course; much bigger, and designed to degrade far less than they used to. But these changes have created other knock-on effects, and new materials in the compounds - used to achieve the target of less thermal degradation set by the teams and the FIA - has meant a reset in terms of understanding how to extract the best from them.

"The [temperature] values are not the same, but we [still] have the hard and the soft which are high working range, and the medium, super-soft and ultra-soft that are low working range," Pirelli racing manager Mario Isola tells Autosport.

"It is a bit different to last year, because this family of compounds is different. Last year we had a warm-up phase, grip increasing, peak of grip, then going down and degrading.

"This year, this curve is much flatter, so you have a warm-up phase, [and] in some cases they don't feel the real peak of grip because then the compound is quite consistent and degrading in a much higher number of laps.

"The feedback from the drivers is they cannot feel the peak of grip. In reality, it is because of the stabilisation [of degradation]. Because the materials we are using in these compounds are completely new, the behaviour of the compounds is different.

"We were designing the compounds with a wider working range, but I had this feedback [that the working range is narrower]. Of course everything is new also for us. All the information we collect each race is important to better understand the behaviour of the compound.

"We see some cars that are very quick in qualifying but struggle a bit in the races; some cars are very strong with the race pace but maybe they don't have the qualifying lap strong enough.

"They are learning. It is a big technical change to the past. I think it is not easy to set up the car in a proper way. If you are able to work in the peak of grip you can take out the highest level of grip."

It seems the point at which it is possible to extract the best from the tyres has become vaguer. Previously, the peak of grip was easy to find, and it was more about managing the extreme drop-off. Now, it's about finding a peak that is more difficult for the driver to feel (because the tyres are more durable) and trying to stay there. It is likely this will require more precision in terms of tyre preparation and set-up.

Ferrari has historically been a bit weak at tyre warm-up and fuel economy - two big limitations at this circuit - but seems to have turned a corner in both regards this year.

Certainly Vettel and Raikkonen were having a much easier time extracting immediate performance from the ultra-soft tyre compared to the Mercedes drivers, while Haas team boss Gunther Steiner says the Ferrari engine has improved in "every area" over the winter, which seems to have put it in position to at least race on equal terms with Mercedes, even if it is still lacking a tenth or two in ultimate qualifying mode.

Mercedes (with Bottas's car at least) seems to be able to get the tyres working eventually over a long run on high fuel, but that will be of little use if Ferrari locks out the front row of the grid and disappears into the distance in the early part of the race while the Mercedes drivers are still warming up.

Mercedes plans to try some set-up tweaks in final practice on Saturday morning in a bid to cure the problems it suffered on Friday, and team boss Toto Wolff certainly feels his team is not facing another potential Singapore 2015-style disaster.

"It was a difficult day, a lot to analyse and a lot to learn," said Wolff. "Cars and teams being offset in pace, some quicker than expected, some slower than expected. It's about just looking at all the data, and putting the car in the right window.

"You could see you needed a couple of laps to put the tyre in the window, and you needed to have clean laps, then it's easier. And if you haven't got the clean laps, you won't be putting it in the right spot.

"The Ferrari seems to be a car that is pretty robust in a wider window of temperature than ours, and it doesn't matter whether it's Bahrain, where it's very hot, or Sochi where it's cold. It's just a very good car.

"There's a pretty good indication what's happening. In Singapore 2015 we were the only team out of position, and we just couldn't make the tyre work. What you can see is there is one team that is extremely fast today, for whatever reasons. There are pretty good clues [for us]."

If Mercedes can follow those clues effectively there is every reason to think it will be back on form for the business end of the weekend, and a contender for victory in a race it usually dominates.

If not, then Ferrari will have a wonderful opportunity to strike another big blow to Mercedes' world championship ambitions.