Why Baku is exposing Mercedes again

If Mercedes was hoping to come to Baku and launch its recovery during the Azerbaijan Grand Prix weekend, Friday practice will have come as a rude awakening. If anything, Mercedes is worse off than it was when it was defeated in China two weeks ago and both Red Bull and Ferrari look to have a decisive advantage.

The Mercedes still shows glimpses of prodigious underlying speed. But if you can't unleash that consistently, be it over a single qualifying lap or a full race stint, then it counts for nothing. Baku is throwing up many of the challenges Mercedes has fallen short in facing so far this year - and there's no sign yet things are going to get any better.

"They are both currently ahead still as they were in the last race but more so today," said Lewis Hamilton of Red Bull and Ferrari after a difficult day - adding that he was going to be banging on the door of the engineers' room to find a way to turn things around.

All is not lost yet. On single-lap pace, Hamilton set the fastest first sector of all and the gap of around eight tenths to the front did not accurately represent the underlying pace of the car. But that means nothing without mastering the black rubbery bits that connect the car to the track - that is where Hamilton and the engineers will be looking.

When you are battling to keep the tyres in the right performance window, be it struggling to keep the rear tyres alive for a full qualifying lap, having difficulty warming up both axles for a fast lap or whatever, the way this weekend has started is bad news. This is not what Mercedes wanted to face after its troubled start to the season.

On long runs, look at a small set of data and things don't look too bad. But then look at what happened to Valtteri Bottas a few laps into his ultrasoft long run, admittedly on tyres that he had done three 'push' laps on, and things look concerning. Yes, the pace could be brought back with some cool-down work, but it's an added complication Mercedes doesn't need.

If you need to manage the tyres in the race, and everyone will need to here, then you don't need that extra concern - especially with the fact the track temperatures will drop a little during the late-starting race and that there are shadows in some parts of the track that mean it will vary from corner to corner.

The track should improve as the weekend progresses in terms of grip, as it did during the first day. That should help the ultrasofts as a race tyre, although just as in China two weeks ago the thermal degradation on those seems potentially to be enough to put people off it if they can get through qualifying on the supersofts. But most have heavily weighted their tyre selection in favour of ultrasofts and there aren't many softs or supersofts to go around.

The mutterings are that the extent of Ferrari's aerodynamic trimming out will be significant

Pirelli is confident a one-stop race will be effective and that that 0.9 seconds difference in peak performance between the ultrasofts and the supersofts will mean Q2 is an ultrasoft affair. But there will surely be plenty of teams wondering about using supersofts in Q2 to start the race on them, and doing a one-stopper using supersofts and then softs, the performance of which is similar. Although unless Mercedes finds more speed, it hasn't got the pace to consider doing that and still make Q3.

Looking at qualifying simulation pace using the ultrasoft Pirellis, it seems Red Bull should be favourite for pole position. But given Sebastian Vettel didn't produce the lap time he should have done (even if you put his best sector times together, he would only have posted a 1m43.805s) and Kimi Raikkonen was so close to Daniel Ricciardo, Ferrari will be favourite on Saturday.

Vettel used the word 'trim' after the session when talking about fettling the car for Saturday, suggesting he will look to boost straightline speed and sacrifice a little downforce. The mutterings are that the extent of that trimming out will be significant. Given the strength of the Ferrari engine, that could well make all the difference in the battle for pole position. The smart money is on the reds.

Here's how the single-lap pace stacks up, based on qualifying simulation laps using ultrasoft rubber. Noticeable is the fact Mercedes is closer to best-of-the-rest McLaren than the front - and by some margin.

Single-lap pace

1 Red Bull (Ricciardo), 1m42.795s
2 Ferrari (Raikkonen), 1m42.864s
3 Mercedes (Bottas), 1m43.570s
4 McLaren (Alonso), 1m43.700s
5 Force India (Ocon), 1m43.814s
6 Renault (Sainz), 1m43.834s
7 Haas (Magnussen), 1m43.977s
8 Williams (Stroll), 1m44.459s
9 Toro Rosso (Gasly), 1m44.712s
10 Sauber (Leclerc), 1m44.940s

Red Bull looks decent on single-lap pace and very good indeed on race pace. Given the ultrasofts did not last long, it's difficult to draw too many conclusions from Friday's race simulations. And what conclusions are drawn might be irrelevant if the frontrunners choose to set their Q2 times on supersofts and try to complete the race without touching the ultrasofts.

But on long run pace on supersofts, Red Bull was also fastest. Ricciardo was six-and-a-half tenths quicker than Vettel on that tyre, and Max Verstappen looked to have even more pace but only completed three quick laps on his long run.

On the ultrasofts, Mercedes looked strong for a few laps - in fact over the first three laps Hamilton was a shade faster than Ricciardo - but then the pace for both drivers falls off a cliff. As such, in our averages his run has been credited over four, rather than five laps as for the rest to avoid his average being dropped unrealistically low.

Even with that, things don't look good - although it's misleading to think Force India and Sauber will really be ahead on race pace, because they won't. On Friday it seems the Mercedes drivers went a little too hard on their tyres, which might have been a deliberate strategy to see how the ultrasofts responded. But even though overnight work will help, it again paints a picture of a team with pace but having difficulty using it.

Long-run pace (ultrasofts)

1 Red Bull (Ricciardo), 1m47.412s
2 Ferrari (Vettel), 1m47.746s
3 Force India (Perez), 1m47.749s
4 Sauber (Leclerc), 1m48.139s*
5 Mercedes (Hamilton), 1m48.221s*
6 Renault (Hulkenberg), 1m48.272
7 McLaren (Alonso), 1m48.662s
8 Haas (Grosjean), 1m48.729s*
9 Williams (Sirotkin) 1m49.506s
10 Toro Rosso (Gasly), 1m49.545s
*Based on a four-lap average

The Sauber pace is probably anomalous as counts only four laps, and Charles Leclerc had a few cooldown laps. But the Force India has looked good and this proves it's a credible threat in the best-of-the rest battle for the first time this year.

But the team that should be happiest going into the race is Red Bull.

"We were quick today," said Ricciardo. "The ultrasoft long run we could have been better, but the supersoft was good. We're pretty confident.

"[In] qualifying, I'm still not sure how much the others can go quicker. Even if we don't qualify, say, front row, we'll still have a very strong race car. We're still in the group of favourites."

Hamilton did look stronger on the softs, matching the pace of Vettel's supersoft run, while Raikkonen was also at a very similar pace using the softs. But it's also worth bearing in mind Bottas has been on strong form recently, and given he always goes particularly well on low-abrasion surfaces (the Baku track has become smoother since last year, according to Pirelli), he could lead the charge for Mercedes.

Much will depend on the changes Mercedes makes overnight and whether it can master the tyres to unleash the pace that is in there somewhere. In qualifying, with the possibility two warm-up laps might be ideal and problems keeping the rears alive late in the lap, Mercedes will have a fight on its hands. And if temperatures are lower, the problem of tyre graining could increase. These problems have been manifest all year, and it's worth taking a close look at the nature of the problem.

In Australia, there was much talk about high-performance qualifying engine 'party modes' after it was nip and tuck with the Ferraris until the final run of qualifying, but it was all about tyre preparation.

Thanks to being stuck behind Ricciardo on his final out-lap, Hamilton backed off dramatically in the last sector. While he had struggled to avoid overheating the rear tyres on previous runs, now they were at about the right temperature to nail the lap, with the rear end planted in the crucial final sector rather than becoming overheated.


If it was easy to explain where specifically the Mercedes problem lies, then it would have been solved

Given the difficulties Mercedes was having in keeping the rear tyres alive for a whole qualifying lap, Sakhir was always going to be a tricky track for the Silver Arrows. It's one where Mercedes, despite good results, has often struggled in recent years and is a traction-heavy circuit. But Shanghai was a different story, a track where Mercedes had generally been strong and which is front-axle limited.

During Saturday morning practice, Mercedes struggled to avoid overheating the rears for a flying lap on the ultrasofts but, in trying to protect them on the out-lap in qualifying, it lost temperature in the fronts. This was down to a combination of the low track temperatures, and the fact that there are two long straights before the long first corner that demands so much of the front left.

Mercedes couldn't protect the rears without the fronts suffering thanks to the low temperatures. So it was no surprise that most of the time loss to Ferrari came in the first half of the lap.

Mercedes has generally struggled more with this on the softer Pirelli compounds, which have a lower temperature working range. The ultrasofts and supersofts have a working range of 90-110C, compared with 105-135C for the softs. In this range, the tyres are chemically 'switched on', meaning you get maximum grip, so on ultrasofts you'd ideally want to start low in the range and end at or near the top of it. But go too high and you lose grip.

You may think it's easy enough to control the temperature, but it's an inexact science because these temperatures apply to the bulk of the compound, the temperature of which can only be inferred by measurements from the surface above and the carcass below.

"These are the temperatures you must have in the compound to make it work," explains Pirelli racing manager Mario Isola. "You have the surface temperature that can be different because you slide so it's more spiky, but this does not mean you lose performance because when the temperature goes down you get it back.

"The carcass temperature is a good indication for teams to understand if the bulk is working at the right temperature. They usually calculate an average of the surface and carcass because we don't have sensors inside the compound."

The trouble is that the way energy goes into the tyre varies and is dictated by a wide range of characteristics. From the moment the tyres are pre-warmed before being bolted onto the car, teams are exerting a chemical effect on the rubber.

"There are a lot of characteristics," says Isola when asked what factors in a car dictate the tyre temperatures. "The level of downforce, because obviously if you push down the tyre you can make it slide less and this increases the temperature less, but you generate more energy because you stress the tyre.

"The suspension geometry [has an impact], and the balance between the front and rear as well. If you are too heavy on one of the axles, you generate additional degradation
on this axle, so they protect the rear axle."

This is what dropping in and out of the window means. Too low 
or too high a temperature and you get more sliding, less grip and less performance. If it was easy to explain where specifically the Mercedes problem lies, then it would have been solved. Mercedes does have unusual front-suspension geometry, which will have an impact on the front/rear balance of the car and, combined with the aerodynamic characteristics of the W09, could be contributing to the problem.

Realistically, it will be a delicate confluence of factors, both inherent to the car and external, that are causing this problem. And if Mercedes is to end its unprecedented (in the V6 turbo hybrid era) victory drought in Baku this weekend, that is the challenge it must master.

If it does so, it will prove that the amount of work that will inevitably have been put into this area in recent weeks has paid off for a team that, lest we forget, for all its troubles is still leading the constructors' championship.