Tyres degrading and falling off the cliff

[she_spools_180]

With this year's tyres being very obvious in their degradation, I have a few questions about how this happens. So I suppose this question is not F1 specific, but it makes it easy to base the conversation around it. However, I do understand that the Pirellis have been engineered to degrade, but my question is about racing tyres in particular, as they all seem to all have this characteristic that I am about to describe.

So my understanding of the structure of a (road) tyre is that on top of the canvas sits rubber. Now when people speak of 'tread depth' of xxmm even on a slick tyre, I have assumed this to mean that there are essentially xxmm of usable tyre compound, and then canvas, or another layer of rubber or something between the canvas for structural reasons.

I can't imagine that a racing tyre would be THAT much different. so my question:

Considering a slick race tyre, if you have xxmm of tread, it should be all the same compound? So why is it, that when the tyre wears, the grip levels drop? Does this have something to do with the degradation of the compound due to heat? This is taking a situation where the tyres have been treated well, and not abused.

The way I see it, it should theoretically retain close enough grip levels to as when it was new, up until the first bit of canvas is exposed (or whatever intermediate layer there might be between the compound and the canvas)

Or is this gradual degradation intentional?

The only thing I can think of, is that perhaps race tyres have been specifically engineered to degrade gradually over the full tread depth, so as not to have almost instantaneous grip degradation when (if) do you reach the canvas/intermediate layer.

Cheers

[DaveW]

I would like to add that the "Pirelli marbles" look rather similar to those generated by the Indy grooved surface, as posted by WilliamsF1. Do you think there might be a physical cause for this?

[marcush.]

With this year's tyres being very obvious in their degradation, I have a few questions about how this happens. So I suppose this question is not F1 specific, but it makes it easy to base the conversation around it. However, I do understand that the Pirellis have been engineered to degrade, but my question is about racing tyres in particular, as they all seem to all have this characteristic that I am about to describe.

So my understanding of the structure of a (road) tyre is that on top of the canvas sits rubber. Now when people speak of 'tread depth' of xxmm even on a slick tyre, I have assumed this to mean that there are essentially xxmm of usable tyre compound, and then canvas, or another layer of rubber or something between the canvas for structural reasons.

I can't imagine that a racing tyre would be THAT much different. so my question:

Considering a slick race tyre, if you have xxmm of tread, it should be all the same compound? So why is it, that when the tyre wears, the grip levels drop? Does this have something to do with the degradation of the compound due to heat? This is taking a situation where the tyres have been treated well, and not abused.

The way I see it, it should theoretically retain close enough grip levels to as when it was new, up until the first bit of canvas is exposed (or whatever intermediate layer there might be between the compound and the canvas)

Or is this gradual degradation intentional?

The only thing I can think of, is that perhaps race tyres have been specifically engineered to degrade gradually over the full tread depth, so as not to have almost instantaneous grip degradation when (if) do you reach the canvas/intermediate layer.

Cheers

in laymans terms ..as the tyre tread depth reduces you got less rubber getting worked and chewed(shear ?) -so less energy is transformed into heat (and the at the same time less stick will be released from the compound) additionally you put in less energy with lower vehicle mass even that ma be a lesser factor compared to downforce and braking.
so with less rubber on the tyre remaining you will eventually arrive at a point where it is impossible to put any force into the tyre but you will simply shed off the rest of the rubber instead.
It´s like a rubber/eraser it will not stick really it will peel off the material instead.

[Jersey Tom]

Marcus hits one aspect of it. Less rubber on the tire = less energy loss per revolution = reduced operating temperature. If the tire does need X amount of temperature to work reasonably well, eventually you cross this threshold and the tires are junk.

Furthermore, as you add heat history to rubber (integral of temperature over time) you will change its properties.

On top of that, the more you mechanically work the carcass (or even just a sample of rubber in general) it will change with strain history.

So from beginning to end of stint you can have a tire with different spring rate, different rubber properties, and working at different temperature range.

[Jersey Tom]

I would like to add that the "Pirelli marbles" look rather similar to those generated by the Indy grooved surface, as posted by WilliamsF1. Do you think there might be a physical cause for this?

There sure is

[radosav]

could depression speed-up tyre falling off the cliff?

[N12ck]

I had a theory with the pirelli tyres, suppose you have 2 layers of rubber, first layer is our lovely grippy slick, then the layer below that is rubber with hardly any grip whatsoever, so when you hit the 'cliff' you are actually just wearing down to the second layer which isn't as fast as the first layer,

what do you think?

[radosav]

I had a theory with the pirelli tyres, suppose you have 2 layers of rubber, first layer is our lovely grippy slick, then the layer below that is rubber with hardly any grip whatsoever, so when you hit the 'cliff' you are actually just wearing down to the second layer which isn't as fast as the first layer,

what do you think?

i think you may be right. teams said that layer of rubber is about 0.5 cm thick.

[Jersey Tom]

I had a theory with the pirelli tyres, suppose you have 2 layers of rubber, first layer is our lovely grippy slick, then the layer below that is rubber with hardly any grip whatsoever, so when you hit the 'cliff' you are actually just wearing down to the second layer which isn't as fast as the first layer,

what do you think?

I thought it had been discussed that this is what Pirelli indeed does. Not sure if there was confirmation on that or not. But in any event, you don't need that design feature for tires to go off fast.

[McMrocks]

I had a theory with the pirelli tyres, suppose you have 2 layers of rubber, first layer is our lovely grippy slick, then the layer below that is rubber with hardly any grip whatsoever, so when you hit the 'cliff' you are actually just wearing down to the second layer which isn't as fast as the first layer,

what do you think?

and the camber makes that you reach this layer over a long (or short) time. With negative camber you reach the second layer at the inside of the tyre early than at the outside. This is why the grip degradation is constant.

[hardingfv32]

I had a theory with the pirelli tyres, suppose you have 2 layers of rubber...

This is in fact what Pirelli has stated that it is doing.

Brian

[N12ck]

I had a theory with the pirelli tyres, suppose you have 2 layers of rubber...

This is in fact what Pirelli has stated that it is doing.

Brian

really, not so bad of a guess then

[marcush.]

I had a theory with the pirelli tyres, suppose you have 2 layers of rubber, first layer is our lovely grippy slick, then the layer below that is rubber with hardly any grip whatsoever, so when you hit the 'cliff' you are actually just wearing down to the second layer which isn't as fast as the first layer,

what do you think?

and the camber makes that you reach this layer over a long (or short) time. With negative camber you reach the second layer at the inside of the tyre early than at the outside. This is why the grip degradation is constant.

you add static camber to improve footprint. I´m not convinced you would wear the insides quicker by doing this (within limits) .sure you scrub of the outside shoulder in no time if you err on the wrong side of camber ..the question is how much are these tyres sensitive to cambers anyways ...I have the feeling it´s more to do with how you put heat into the tyres by adding more negative camber (this could lead to putting more energy more directly into the carcass)

As for rubber history ...I remember a time when using yokohama tyres and they were notorious for allowing you not more than a few heat cycles....they looked perfect (at least to me back then .. )but there was no life in them anymore...it was like iceskating ...

[Belatti]

Cam ploted this here



If you look Alonso`s laptime at lap 58 at the Canadian GP, you could support the theory of the 2 compound layers.

Before reading this theory, mine (with no evidence to support it) was that 2012 Pirellis were more like cooking rice when you boil it with not enough amount of water, or like a chemical reaction that endures till one of the components runs down.

[strad]

Last race they were real clear it was temperature related..105°C and once they go beyond it, they won't come back. I'd have sworn it was broadcast on, perhaps the McLaren team radio....Now I have to go watch and clip it...I remember cause I had to run and see that it converts it to 221°F