Thoughts on 2012 tyres?

[strad]

I suppose that is the reasoning...I couldn't figure why they wouldn't want more tires myself.

[raymondu999]

http://www.autosport.com/news/report.php/id/99856

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."

[Sombrero]

Not long ago (21/05/12) I read this about the Pirelli tyres in F-1.

http://memoiresdestands.hautetfort.com/ ... olcan.html

Bernie Ecclestone and Pierre Dupasquier had a phone call when Bernie decided to take Pirelli in F-1. He wanted to know his opinion.

Pierre Dupasquier told him : "You know them, they are nice people, italian engineers are extraordinary, they are genius and they have also fantasy, they are easier to come with than the french but there is a major setback that they may be have solved this days (or not) : They simply don't know to make two tyres the same. It doesn't matter much for road cars but it's a problem for F-1".

Bernie answered : "I know and that's okay. I said to Pirelli, do the same --- (!) as you did when we were together at Brabham. We took the start never knowing what would happen during the race".

-

[N12ck]

I am starting to get slightly annoyed with f1 become a tyre endurance race rather than an f1 race, Who thinks bring back bridgestones or last years pirellis?
Nick

[McMrocks]

me too

[ESPImperium]

Im thinking about bringing back the 2006 regs where you have to choose the compound for each car by 2 hours after FP2.

Give the guys 4 sets of tyres for FP1 and FP2 with 2 options and 2 primes, the for FP3 you get a single set of your chosen compound then 5 sets for Quali and the race. And when it comes to Quali, you have to set a time in each session or you go to the back of the grid.

Conceivably it could mean that Pirelli take 3 compounds to each race, and drivers can choose the two they like the best.

[Crucial_Xtreme]

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...

McCabism

[strad]

Couldn't a lot of that be offset by pressure change? or at least some of it? It would affect the amount of deformation heat. wouldn't it?

[richard_leeds]

By popular request, the impact of F1 on Pirelli marketing has its own thread so we can keep this one technical.

viewtopic.php?f=1&t=12841

[McMrocks]

Is Pirelli able to make a bigger working window? I mean some teams aren't able to make both compounds work.

I watched Indy 500 yesterday. There i saw real racing

[Jersey Tom]

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...

McCabism

Erm...

For one, who is to say where the teams have their blankets set? Where is this information coming from? If it were me I'd want no part of my tire sheets or setup info leaving my time, much less floating around in the public domain. Second.. a "flatter" footprint? ('contact patch') What does that even mean?

Everything else really gets into speculation / assumption / hand waving. The positive vs negative feedback loop thing in particular. Isn't clear if it's really referring to temperature or to actual degradation. Any and all heat history on rubber is going to evolve and change or degrade it. Heat history = area under the curve of temperature against time. Doesn't matter if you're in the "optimum temperature range" or not.

Also not sure I agree with the various teams "sliding" around more or less because of varying degrees of downforce. In an absolute sense, even the cars in the F1 grid with crap downforce.. have a lot of downforce. High downforce, big tires, low inertia... I'd say none of the cars are sliding around on fresh tires - as you'd see in other racing series with more sedan body types and heaps less down force.

So many other assumptions in there. That the "optimum operating band" is between 85 and 100C? Says who? Pirelli released that? Who is to say they know what the best range is? Best for what? Ultimate traction? "Grip"? Longevity? Wear?

Sometimes sounds like we're also assuming the 2011 tires were better than 2012. I recall tires in 2011 - particularly early on - disintegrating in "powdery wear" and giving up seconds a lap.

And as an aside - I agree the racing at Indy yesterday was quite good.

[hardingfv32]

1) Pirelli say that its tire operate at a high temperature range this year. Does that in itself represent an difficult issue for the teams?

2) Why wouldn't the driving style of one of the F1 drivers be able to cope with the narrow temperature range? Say, sensing when the tires are out of range and making driving changes. Would it be hard for the driver to know if the tire is on the low or high end of the temperature curve?

Brian

[JohnsonsEvilTwin]

2) Why wouldn't the driving style of one of the F1 drivers be able to cope with the narrow temperature range?

Maybe its a case of getting it into the range firstly, and then keeping it there.
As in the case of Button/Hamilton.
Seems the Pirelli strategy has come full circle and it is button who now struggles with a smoother driving style being unable to get the required initial start up temps into the rubber which then has a knock on effect for each and every prevailing lap.

[Jersey Tom]

Why wouldn't the driving style of one of the F1 drivers be able to cope with the narrow temperature range?

I don't really think so, no. Just how specifically would you suggest they do this?

You go out and drive with the intent of going as fast as possible (at least, until your team radios you to slow down and conserve tires / go into parade mode). If you can't get enough heat into the tires... you're hosed. You're already driving as hard as you can, to max accel at any point in time. That's what generates heat - load and deflection.

And if you're overheating the tires, then what? Back your pace up 0.5 sec a lap and let everyone else go by?

[raymondu999]

I'd suspect car mechanical setup as well as downforce levels would have a much bigger say in tyre temp, no JT?