Why F1's competitive order has been mixed up at the Singapore GP

Fifth-placed Lewis Hamilton was over half a second slower than the next fastest car (Daniil Kvyat's Red Bull), and well over a second away from Sebastian Vettel's pole lap.

We're used to seeing Mercedes top sessions by those margins, not be on the receiving end.

The drivers expressed no real dissatisfaction with the handling of the W06 after the session.

From trackside, the car looked well-balanced in final free practice, and Hamilton said afterwards that he had "100 per cent confidence in the car".

Mercedes has "no explanation" for pace

The problem was not one of balance, but simply a lack of overall grip.

So what went wrong?

The problem likely has it roots in a combination of the track layout, the characteristics of Pirelli's super-soft tyre, and how Mercedes has made use of that tyre in Singapore.

Mercedes boss Toto Wolff referenced this in his post-session media briefing, when he described the Marina Bay circuit as a "very special track" and talked of searching for "the sweet spot of the tyre".

MASTERING THE SUPER-SOFT

Engineers within the paddock say Pirelli's super-soft is what's known as a 'low working range' tyre, which broadly means it's easy to overheat.

But the super-soft is also a compound that Williams performance chief Rob Smedley describes as "very peaky", which means the range of working temperatures to which it will respond is very narrow.

"It's on a knife-edge," he said. "And if you get it dead right then it rewards greatly, and if you don't get it spot on then it can be more than the usual few tenths that you're off the pace."

More commonly you may expect the problem with this tyre to be one of over-working it, causing a fragile compound to lose performance rapidly over the course of a lap.

This seems to be what happened to Romain Grosjean on his Q3 run, when he got wheelspin at Turn 6.

As soon as that happened, he got further wheelspin at Turns 7 and 8 as the rear tyres ran away with overheating, dropping over the hot side of the peak temperature range and costing him rear grip.

You also get some drivers struggling to get the front and rear tyres balanced.

Sometimes the front tyres are not hot enough for the first part of a flying lap, so drivers lock their brakes and lose time through the first sequence of turns, while in the meantime the rear tyres get worked too hard and start to lose performance towards the end of the lap.

This is what happened to Sauber driver Felipe Nasr, who failed to escape Q1 in the updated C34. The car is still weak over the bumps and struggles for traction, which means the surface of the rear tyres can easily overheat and cause an imbalance.

According to Smedley, there is "no single factor" that dictates correct tyre preparation for a particular car, or how that car/driver combination extracts maximum grip from the rubber.

"It's based on a number of factors," he added. "The preparation before the tyres leave the garage, how much energy your car puts into the tyre around the lap, sliding energy, sliding velocities around the lap - and therefore the range of temperatures the tyre sees, not just the single average temperature.

"[Also] whether you can keep it keyed into a small temperature range, or whether because you've got more sliding you're tending to go both sides of the peak."

A UNIQUE TRACK

The layout of Singapore's Marina Bay circuit could also play into explaining why Mercedes struggled here relative to its opposition.

Red Bull and Ferrari were both much closer to Mercedes here than at any other track on the calendar during the 2014 campaign.

The layout places a premium on good braking, strong traction, and skilful driving, while the influence of engine power is greatly reduced, as is the effect of downforce variation between the cars, because most of the corners are of short duration and low speed.

That means Mercedes' usual strengths - high-speed corners and long straights that require efficient recovered energy deployment - are not so evident here.

Of course, Mercedes was very fast in Monaco, where the track is similar in terms of demands, and the same tyre compounds are used, but Singapore is much hotter than Monaco, and the circuit is also much longer, which places far more of a premium on tyre management.

So how quick anyone can be here is about how well the drivers and cars can work and manage the tyre, which is a very complicated and tricky process to get right in this era of high-degradation Pirelli rubber.

It's something Red Bull and latterly Ferrari have been extremely good at in the past, and it has not been one of Mercedes' traditional strengths.

The differences could be exacerbated by the length and layout of the track, according to Smedley.

"The tyre is constantly working here, but there are no high-speed corners, so you're not imparting a huge amount of energy into the tyre," he explained.

"We have quite a high value of sliding velocity, so the way the tyre scrubs across the surface of the track.

"You get quite a different relationship here between the bulk temperature and the tyre surface, and it's knowing the key to both of them and how to target both of them.

"There's also not a lot of recovery for the tyre around the lap, so once you put it into a certain situation, trying to recover from that is very difficult.

"On a normal circuit you have a kilometre of straight to recover and it doesn't really remember what it's done a kilometre ago. Here you never stop using it."

This is why Grosjean couldn't recover after his Q3 wheelspin.

The vagaries of the rubber, and the relationship between surface temperature and bulk temperature is something that also confounded McLaren's Jenson Button, who wound up nearly seven tenths adrift of team-mate Fernando Alonso in Q2.

"My second run in qualifying I always picked up massive understeer," he explained.

"We think it's because the brakes get hot. Normally you use the brakes to warm the bulk tyre temperature, and you don't want to raise the surface [temperature] too much.

"I think I was putting too much temperature into the fronts, so always on my second run I had massive understeer even though we put a lot of front wing in.

"I struggled with the tyres today, I'm sure a few others did. I just could not read them at all."

The Mercedes drivers complained of a lack of grip generally, and the early suggestion from within the team is that the W06s were operating the tyre below the correct working range.

Thus the car was well balanced, but just not 'switching on' the tyre enough to go fast.

Why exactly Mercedes could not get the super-soft tyre up into the correct range is still unclear.

"To do that you need to have all the matrices right," explained Wolff. "Rideheight, camber, torque, pressure, temperatures. There is so much influence. This is a new one for us."

The driver also plays a large part in this process, in terms of how they drive their out-laps and 'prepare' the tyres for a quick run.

Small variations in this process between drivers in the same car could explain why Grosjean made Q3 while Pastor Maldonado - complaining of a general lack of grip - could only qualify 18th, or why poleman Vettel was nearly eight tenths faster than Ferrari team-mate Kimi Raikkonen at the end of Q3.

There wasn't ultimately a huge gap between Rosberg and Hamilton (0.115s), so there's unlikely to be a huge variation between the two drivers in the way they managed the tyres.

It's thus more likely to be something related to the set-up of the car.

The team's only hope now the cars are in parc ferme is that things will turn around when every car on the grid is fat with fuel and running on used rubber.

Regardless, F1's usually dominant force faces an uphill struggle to win the Singapore GP from here.