Why Mercedes lost out to Red Bull in practice

If ever there was a track where you may expect someone to genuinely knock Mercedes off its perch at the top of the Formula 1 tree that circuit would surely be Monaco.

After all, it is here, around the famous streets of Monte Carlo, where pure horsepower counts for far less than it does elsewhere in F1. Given Mercedes has dominated largely (though not solely) because of the superiority of its engine under the V6 hybrid turbo rules, Monaco is the place where it is naturally most vulnerable to attack.

Pre-season many would expect that challenge, if it came, to come from Ferrari. But Ferrari has struggled to string a weekend together so far, sometimes fast on Friday then losing ground when it counts, other times slow on Friday and not quite managing to recover in time.

Here Ferrari is struggling to begin with, slipping unexpectedly behind customer squad Toro Rosso (which uses the 2015-spec engine) in the pecking order.

"We didn't have a good day, so I don't think we belong where we are in the standings," reckoned Sebastian Vettel, the slower of Ferrari's two drivers after a couple of costly contacts with the unforgiving Monaco barriers.

"It will be better on Saturday. For today it was not the main focus to be high up. The running we had was a bit scrappy.

"The pace is in the car. I struggled a bit to get it out. We tried a couple of things. It's fair to say that some of them didn't work."

Ferrari dug itself into a set-up hole during qualifying for the last race in Spain, which allowed Red Bull to steal an opportunistic victory when Mercedes' drivers crashed into one another, and here the Milton Keynes team looks certainly to be Mercedes' biggest threat.

Red Bull struggled here last year, qualifying more than seven tenths of a second adrift of pole having been within four tenths of the outright pace the year before - though that was helped by the escape-road incident that nullified both of the Mercedes drivers' second runs in Q3.

But last year's RB11 was a difficult car for the first half of the season, until Red Bull introduced an aerodynamic upgrade that allowed it to unlock that car's full potential.

This year's RB12 has clearly built on that late-2015 success, and now looks like a seriously good chassis - perhaps the best on the grid.

But the chassis is nothing without a decent engine. As Jenson Button points out "we don't pedal the cars around".

And Red Bull now has the best Renault engine yet under these regulations powering its car. A positive test at Barcelona's Catalunya circuit last week prompted the French manufacturer to introduce its latest power unit here, a race earlier than originally planned.

Daniel Ricciardo utilised his RB12, and that new Renault engine reckoned to be worth 0.15-0.2s per lap around Monte Carlo, to stunning effect to comfortably outpace the entire field during the second free practice session for this year's Monaco Grand Prix.

He ended the day 0.606 seconds faster than Lewis Hamilton's Mercedes. The last time a Red Bull was at least that much faster than a Mercedes was in qualifying for the 2015 Singapore GP, when Mercedes was busy losing its way with super-soft tyre temperatures.

PURE PACE RANKING (ultra-soft)
1. Red Bull (Ricciardo) 1m14.607s
2. Mercedes (Hamilton) 1m15.213s
3. Toro Rosso (Kvyat) 1m15.815s
4. Ferrari (Raikkonen) 1m16.040s
5. Force India (Perez) 1m16.120s
6. McLaren (Button) 1m16.325s
7. Haas (Gutierrez) 1m16.782s
8. Williams (Bottas) 1m16.849s
9. Renault (Magnussen) 1m17.530s
10. Sauber (Ericsson) 1m17.562s
11. Manor (Haryanto) 1m18.647s

But how genuine is this Red Bull form? Can it really go from Spanish opportunist to actually challenging for victory in Monaco on merit?

Ricciardo was naturally delighted with his own efforts. He should be. One top technical director described his lap as "stunning".

But even within that justified delight Ricciardo sounded a serious note of caution for the rest of the weekend.

"I know they [Mercedes] always have a little bit more for qualifying," he said. "I know they're able to get a bit more power out of the engine on Saturday afternoon.

"I don't think it's six tenths, but I expect qualifying to really close up. Today obviously I'm happy, but not getting too excited.

"I'll be surprised if we can keep that gap."

We know Mercedes will turn its engines up for qualifying. We know Mercedes will have more margin when it does this than Red Bull will. But as Nico Rosberg pointed out: "Of course we can still turn up our engine, but we don't have six tenths of turning up the engine..."

Perhaps more critical here will be how Mercedes unlocks the potential of the ultra-soft tyre.

This is the first time Pirelli has brought its softest available compound to a grand prix, and Mercedes was unique among the top teams in declining to sample it during pre-season testing.

Monaco features a very different track surface and weather conditions to Barcelona in February (smoother and hotter), so that decision was understandable, but nevertheless Mercedes will naturally have less data available on how this particular compound works than its main rivals.

Pirelli says the gap between the ultra-soft and super-soft here should be somewhere between 0.8 and 0.9s, but of those who did proper runs on super-softs in the early part of FP2 (Hamilton, Rosberg, Carlos Sainz Jr, Fernando Alonso, Jenson Button, Kevin Magnussen, Marcus Ericsson and Felipe Nasr) only Rosberg (0.911s) found anything like that amount of time when he switched to ultra-softs.

The rest ranged anywhere from 0.003s (Alonso) to 0.626s (Button). The mean gain was somewhere between 02-0.4s.

The reality is probably that Rosberg underperformed on the super-soft and Mercedes generally underperformed on the ultra-soft.

The ultra-soft is not that much different to the super-soft in reality. Hamilton described the tyre as "a super-soft with purple paint", and Pirelli says the working range of temperatures for the two compounds is very close.

Mercedes had problems getting the super-softs to work in Singapore last year, but that was a clear one-off and it's unlikely to have fallen into the same trap again.

More likely it was simply using practice to try experiments that didn't quite work, and will come out all guns blazing on Saturday as usual, after spending Friday's rest day to do its homework properly.

"I didn't even know it was six tenths," said Hamilton of the gap to Red Bull. "I've not really been looking at that, I've just been focusing on getting the set-up right.

"There's a little bit of time left in my lap. These tyres are pretty solid - sometimes we're able to warm them up, sometimes you don't get enough heat in.

"They're very strange with the way they switch on and off. So we're trying to figure out whether we're maximising the potential of the tyres."

Not only was Hamilton only 0.276s quicker on the ultra-soft compared to his earlier super-soft run, he was also just over a tenth slower than his pole position lap from the previous season - despite driving a faster car and using softer tyres, on a circuit that has been resurfaced in places and redesigned slightly, making it faster through the Swimming Pool section.

This all suggests there is much more to come from Mercedes than we've seen so far. If the engineers unlock the full potential of the ultra-soft tyres then history suggests Red Bull will be realistically looking at locking out the second row of the grid, rather than challenging for the first.

If not, well then all bets are off...

As ever at Monaco qualifying will be the most crucial session of the weekend. Degradation on both of the softest available compounds is almost non-existent on Monaco's smooth surface, so don't expect a barrage of pitstops or many mixed-up strategies.

Ricciardo did a 20-lap long run on a well-used set of ultra-softs at the end of FP2, and his penultimate flying lap was only fractionally slower than his first.

So those teams that struggled on Thursday will need to get their acts together for Saturday, or potentially face a frustrating 78-lap race stuck behind slower cars.

Ferrari should expect to jump into the top six at the business end of the weekend. Toro Rosso certainly thinks its engine supplier will. But Ferrari could be struggling to challenge Red Bull here, given the strength of the RB12 at low speed.

Again, much will depend on how Ferrari understands how to extract performance from the ultra-soft tyre, while also turning the sort of mistake-free laps its drivers struggled to produce in practice.

Toro Rosso should expect a tough fight with Force India and McLaren for the final spots in the top 10. Sergio Perez was not particularly happy with his car or his driving on Thursday, but he lapped within 0.305s of Daniil Kvyat's STR11, and will have the benefit of extra Mercedes power come Saturday.

McLaren should be a threat if it can dial out some of the excess understeer that plagued Alonso and Button through the first two sessions, without compromising the necessary traction that is so key to a good laptime here.

Newcomer Haas is always much happier on the softer compounds and looks quite closely matched with Williams, which struggles on lower-speed tracks, of which this is by far its worst.

Valtteri Bottas fared better than team-mate Felipe Massa (who crashed in FP1 so lost valuable tracktime), but the penalty for improved turn-in on Bottas's FW38 was a big helping of unwelcome oversteer.

Q3 could be a stretch for Williams here, but the upper reaches of Q2 should be on the cards with that extra available Mercedes grunt, if it finds a better balance with the chassis.

Renault will also be hoping to take a big step forward on Saturday, after "making the car worse" following last week's Barcelona test, according to Kevin Magnussen, who was 17th quickest here and only fractionally quicker than Marcus Ericsson's Sauber.

The chassis has looked very benign to drive previously, and the new engine in Magnussen's car is known to be better than the old one, both in terms of drivability and power.

As Magnussen says, Renault's deficit to pacesetter Red Bull shows all its problems here are with its chassis, of which it seems to have created a few new ones for Monaco.

Red Bull knows it has very few problems (if any) in this area, and a better engine than before, but it's still likely to need a helping hand to beat Mercedes when it really counts.