The 0.4mm difference that may be costing Ferrari

Sebastian Vettel may have been half-joking when he made a plea for help in finding a phone number for the "grip guy" after the Monaco Grand Prix, but it is clear that his Ferrari team thinks its problems in 2019 are mostly tyre related.

Ferrari has dug deep into what has gone wrong over the early stages of the current campaign, and its conclusions are that it has not gone the wrong way with its car concept or that it has a fundamentally bad design. Instead, Ferrari's biggest headache is that it cannot switch on its tyres as well as others.

Finding itself outside the prime operating window for the tyres at times has left Ferrari lacking the ability to extract performance, especially in slow-speed corners - an area where Mercedes is able to do so beautifully. Ahead of the Monaco race, Ferrari team principal Mattia Binotto suggested that his team in particular has been caught out by the impact Pirelli's new thinner tread tyres for 2019.

"The tyres of this season are quite different from the ones of last season," he explained. "There is no blame, it is only a matter of fact. The main difference is that last year we had very good warm-up with the tyres and we were all focused and concentrating on cooling the tyres as much as we could to keep them working, because the lower the temperature the better the grip.

"The tyres of this season are quite different in this respect. Warm-up [is] a lot more difficult and what we may call the window, the temperature target of when you have the best grip from the tyres, in order to achieve it, you need to heat up the tyres."

But is Ferrari's theory about its 2019 campaign stalling because of the new tyres really valid, or it is just seeking excuses for a season where it has failed to deliver?

What is certain is that there has been a consequence from Pirelli's move to introduce thinner tread tyres for this year, which was part of a raft of minor tweaks made to the rubber for 2019.

The reason behind the change was to try to eliminate the overheating and occasional blistering that teams and drivers so disliked last year. The best way to do that was to reduce the tyre bulk itself - to ensure there is less rubber to store heat as the tyres work on the car.

The reduction in tread depth was only 0.4mm, but it was enough to cure the overheating issue - with a shift in the tyre temperature working range a resulting consequence.

"This action moved the working range a few degree towards higher temperature," says Pirelli's head of car racing, Mario Isola. "It is not changing the working window itself, because this is a function of the compound and the same compound has the same working window. But it is slightly higher now - so the tyres are overheating less and you can use them on the higher side of the temperature."

A dig through the working temperature ranges of the 2018 and '19 tyres shows how things have moved, with the ranges either moving up entirely, or the top end extending performance to a higher temperature.

The changes may be only a few degrees, but they are enough to require the teams and drivers to adopt a new mindset. They have had to begin their learning processes all over again in 2019.

It's not just about getting the tyres into a 20C temperature window either. Inside that window there is an area that produces the peak performance of the tyre, and it is this magic bullet that the teams now obsess over.

"When there is a championship like this one, when there is a window and you have 4/5/6 teams fighting for tenths of a second, it is not just staying in the window that is important," says Isola. "It is important to find the peak of grip.

"You have a window on a flat part of the curve, where it generates the highest possible grip. And inside this window is somewhere with a bit more [performance]. When you are close you are always hunting for it and the drivers can feel it."

But it's one thing managing a tyre to bring it down to this area of peak performance. What is harder is a situation where teams must try to bring tyres - especially the fronts - up to the right temperature.

"Getting the front tyres hot, that's the main problem - it is very difficult," says Williams's senior race engineer Dave Robson. "Then you get this problem of wanting one thing on Saturday for that one lap, and Sunday you want something different. But [because of the parc ferme rules] you cannot change anything other than the way the driver drives, so it is frustrating.

What works well for high-speed corners on one circuit may not be so good for slow speed

"You see people taking different approaches on their out-laps, and different cornering speeds. I think in Canada you will see different approaches down the straights with people using DRS or not on the out-laps to move load around. But, ultimately, the best way to load tyres is through downforce."

That final point is particularly key for Ferrari's situation. The conclusion that the team appears to be edging towards, and it is not alone in feeling this in the pitlane, is that having a high downforce car this year - even if it sacrifices some aerodynamic efficiency down the straights - pays off handsomely in helping put more energy in the tyres and getting them into the right window.

Some outfits deliberately focused on having very aerodynamically efficient cars for 2019 because of fears that the new aero regs would increase drag too much and leave them vulnerable on the straights. It appears that such a route, which Ferrari pursued with its front wing design, was perhaps not best for the tyres.

But responding to the shortcoming is not as simple as just throwing on downforce and expecting that to help make the tyres come to life. Teams must think about equalising the front and the rear tyres, as well as the aero balance of the whole car.

What works well for high-speed corners on one circuit, may not be so good for slow speed, and vice versa. And what works on tracks with low energy corners such as Monaco may not be needed at circuits with characteristics like Barcelona.

"What they do to set up the car is balance the front axle and the rear axle, and then use the downforce to achieve the level of energy they need to make the tyres work," explains Isola. "It depends a lot on the circuit, circuit layout, and tarmac roughness, because with different circuit layouts you can generate more energy on the front or rear.

"In Baku, for example, the most critical aspect is that you have a circuit with no high-energy corners, and most of them are 90 degrees. You need a lot of traction, you have a long straight, and the asphalt is the smoothest in the championship. So, the hardest job is to balance the front and the rear because the rear is prone to overheating because of the sliding and traction, while it's difficult to keep the temperature [with] the front.

"You cool down the front tyres on the straight, and this year we had weather conditions that were not ideal or warm, so the temperature drop from the beginning of the straight to the end of straight was in the range of 30-40C. And there is nothing you can do.

"You could try to find a set-up that is a compromise to avoid too much understeer and maybe graining on the front, but you cannot kill the rear tyre because of degradation due to the overheating."

It should not be forgotten that the teams are chasing something that cannot be measured. Apart from in laboratory conditions when sensors are placed inside tyres on rigs, there is no way for them to accurately measure the bulk temperature of the tyres when the car is on track. It really is a black art.

Where Ferrari is perhaps most lacking is in its ability to be versatile with its car in relation to how it can load the fronts and rears. Repeated comments about understeer suggest it has maxed out trying to load up the front.

Mercedes' high-downforce concept gives it more options to find the right levels and a good balance - and it may be that having a more benign car is the key. Boss Toto Wolff is open about how a shift of concept has paid dividends at his team.

Canada may offer the best chance to really understand the state of the tyre situation

"In the early days of the power unit regulations we had a car which was a low-drag fast car on the straights and carried with the might of the engine," he explains. "Over the years, I think chassis and power unit have merged in order to extract the optimum lap time. Half that is that the engine is still impressive, but we were able to wrap a chassis around it that has more downforce, and more drag.

"We're not the quickest car on the straight anymore, but we believe that this compromise between these two main blocks of performance works well for us."

Perhaps the Canada race will offer the best chance to really understand the state of the tyre situation, and whether Ferrari really is a bit boxed in by the 2019 tyres. The Circuit Gilles Villeneuve is a power-sensitive track (good for Ferrari), with low energy corners (not so good for Ferrari) - so there could be a tricky downforce dilemma.

"There is definitely the case that downforce and drag don't always do what downforce and drag should do in simple terms because of the interaction with the tyres," reckons Robson.

"The best approach, if you can afford to design the concepts and manufacture and carry the parts around, is to just have options available, and it will be interesting again in two weeks' time.

"People would normally think about taking downforce off for Canada, but if you cannot get the tyres working then maybe that won't work as much as normal. It will be an interesting data point."