Pirelli insists that there is no mystery to its 2012 tyres - and that teams fully understand exactly what they need to do to get the most out of the rubber.
However, the Italian company believes the big fluctuations in form, and various struggles that some teams are having, are the result of those outfits not knowing how to get their cars working with the rubber.
Amid an ongoing focus on the impact Pirelli is having on the racing this year, with five different winners in the first five races, its motorsport director Paul Hembery said: "I would say all the teams understand the tyres – what they don't understand is how to make the interaction between the car and the tyres do what they want. That is the real challenge.
"They know exactly what is going on with the tyre. You talk to some of the tyre experts at teams that, on the outside, appear to be suffering, and the tyre guys explains exactly what it is doing.
"It is not the tyre – it is the interaction between car and tyre to get the tyre in to the window that maximises the performance. I am not trying to shift responsibility: but it is that."
"The biggest issue teams have faced this year is getting their tyres into the right operating window – so they are not too hot that they overheat and degrade, and not too cold that they do not deliver the necessary grip."
Although that operating window is not any narrower this year than it was last year, the 2012 tyres do operate at higher temperatures. That factor, allied to the fact that tyres are having less energy put through them this year because of the move away from blown diffusers, could explain why there have been so many struggles.
"It has moved," said Hembery of the temperature range. "It isn't particularly higher, it has moved higher. But it varies, and it depends what tyre you are talking about.
"There is also the fact that we see the cars oversteering a lot more this year, and if you are oversteering you are sliding, and that can overheat your tyres. That wasn't evident last year because a lot of the cars were very stuck to the ground in simplistic terms, with very little movement on the rear."
Crucial_Xtreme wrote:Very good article from McCabe
A general theory of Pirelli's 2012 F1 tyres
The volatility of this season's Formula 1 season has been attributed to the temperature sensitivity of Pirelli's 2012 Formula 1 tyres. All of the teams are finding it difficult to keep the tyres in their optimum temperature band between 85 and 100 degrees C.
I'd like to propose a theory which explains what is happening. As I see it, there are two key facts, outlined by Mark Hughes in this week's Autosport, which need to be explained:
(1) Ferrari, Williams and Sauber tend to run their tyres hotter than Lotus, McLaren and Red Bull.
(2) In the past, when a tyre overheated, it would lose grip, and the temperature would then fall back into the operating band. This year, when a tyre overheats, it never recovers. Hence, a negative thermal feedback process has been replaced with a positive feedback process.
My theory depends upon the following facts about the physics of tyres:
(i) Tyre grip is generated by two mechanisms, sometimes referred to as physical grip and chemical grip. The first process involves the shear deformation of the contact patch, whilst the second involves the coefficient of friction of the tyre. The internal stress response to shear deformation depends upon the shear modulus of the tyre, which is temperature dependent, and the friction coefficient is dependent on both tyre temperature and slip velocity, (as depicted in the image below from Michelin's tyre modelling efforts). So both mechanisms by which grip is generated, are temperature dependent.
(ii) Tyre temperature is generated in a tyre by the deformation it undergoes, and by the friction associated with tyre slip.
The key difference between this year's Pirellis and last year's, is that the 2012 tyre has a flatter contact patch. I hypothesise that what this has done is to change the balance between the heat generated by deformation and the heat generated by friction, in favour of the latter. This can explain our two key facts:
Firstly, if we accept that Red Bull, Lotus and McLaren have more downforce than Ferrari, Williams and Sauber, then the former teams will tend to suffer from less tyre slip than the latter teams. This explains why the former teams now run their tyres cooler than the latter trio.
Secondly, we can now explain why thermal degradation is a positive feedback process. When a tyre overheats and loses grip, it slides more. When the balance between slip-generated heat and deformation-generated heat has been tipped in favour of the former, a car which slides more will generate ever hotter tyres, leading to runaway thermal degradation. In contrast, in 2011, when a tyre lost grip, the deformation reduced, hence the temperature returned to the optimum operating band.
It's just a theory...
hardingfv32 wrote:2) Why wouldn't the driving style of one of the F1 drivers be able to cope with the narrow temperature range?
hardingfv32 wrote:Why wouldn't the driving style of one of the F1 drivers be able to cope with the narrow temperature range?
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