Tyres degrading and falling off the cliff

[bhall]

According to Pirelli, the super softs' optimum temperature is 95°C; the softs' is 105°C; the medium's is 115°C; and the hard's is 125°C. I don't know what any of that really means, if anything. But, there it is.

Source: Pirelli video, "Tyre Behaviour."

[strad]

Ah good,,Validation.
But I was very tired after work and didn't realize that the question was why?
I think that the heat acting as a catalyst changes the compound. And since I too have had tires that after a few heat cycles became bricks, think that somehow it actually cooks them..Maybe that why so many marbles,, starts being like grating a brick of Parmesan.

[ubrben]

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.

I'd say it's more likely to by 0.5mm

Ben

[raymondu999]

JT - so why use tyre warmer blankets? If you say that the heat history will always have a degrading effect on the rubber, surely that would mean the tyre blankets will degrade the rubber? Or is there something I'm missing?

[bhall]

Tire blankets don't heat tires to their "optimum" temperature. That happens after the tire is fitted and run on-track.

Also, current F1 tires are constructed with the understanding that tire blankets will be used to pre-heat them. When asked about a potential tire blanket ban, Paul Hembery said this year's tires wouldn't work, that their construction would need alteration to cope without pre-heating.

(I'm know I'm not JT; I answered this mostly just to see if my understanding is correct.)

[raymondu999]

Doesn't matter - JT says that heat history will have an impact. Tyre blankets add to that heat history. Not by much, probably. But it still does.

[bhall]

The effect of the tire's construction can't be overstated. Especially when one considers the following...

Pirelli’s Paul Hembery confirmed he would “welcome” the ban but warned it “would require a complete change of the composition” of the tyres. He said the ban should therefore be introduced over two years.

For 2013, Hembery said, warmers for wet tyres could be banned, preceding a full ban for slicks the following season.

Clearly, tire blankets are factored into the equation.

Regardless, which is worse: a marginal loss of longevity or exiting the pits on ice-cold tires? As with everything else in F1, I imagine this is just another compromise, albeit a small one.

[raymondu999]

that's what I was trying to say too. The construction could maybe be somehow altered to prep it for tyre warmers, but if the tyre gets degraded by any and all heat history, wouldn't tyre warmers also contribute a small, albeit probably negligible effect on degradation?

Now if this is the case, why don't they just have 1 set of tyres (maybe 1 set of each compound) ready? Is it just for "just in case" a pitstop goes booboo and they have to fit a different set of tyres instead?

[bhall]

Ah, I see what you're saying now. You're asking, why do teams appear to store their tires within tire blankets given the degradation caused by heat? I thought you were asking, why do teams use tire blankets at all given the degradation caused by heat?

Yeah, you do tend to see a floor-to-ceiling stack of tires in tire blankets in every garage, and that's probably because it's not unusual for a driver to go through 16+ at any given race. That's to say nothing of Friday and Saturday.

[raymondu999]

along those lines. For example, teams save their tyres to have the max number of new tyres for qualifying and the race, which ends up as 3 options and 3 primes. So do these get stored in the heater/tyre warmers until qualifying? Sure the heat is only coming to the tyres at a trickle rate, but if as JT says the heat accumulates to a "heat history" then it would be significant come qualifying.

[Jersey Tom]

JT - so why use tyre warmer blankets? If you say that the heat history will always have a degrading effect on the rubber, surely that would mean the tyre blankets will degrade the rubber? Or is there something I'm missing?

Storing tires at elevated temperature for extended periods of time is probably not ideal, unless you're intentionally trying to over cure the thing.

On those tires you still have to pre-heat them before going out or they'll be junk on the first several laps but I'd say it's probably a question of how far in advance you flip on the heater. And just because you see a tire wrapped in a blanket doesn't necessarily mean the thing is on - just covered.

[ubrben]

Let's be clear to, any "hardening" or "post-curing" of the rubber due to heating blankets is not the same thing as the rubb er properties being strain history dependent.

The effect of tyre warmers is as much about increasing the tyre pressure. This will increase the tyre stiffness and give the driver confidence to push. A classic situation with powerful RWD cars is the driver spins the tyres off pitlane has reasonable grip at the rear, nothing at the front and spends the next few laps bitching about understeer and a lack of front support.

When you take a tyre out of warmers the suface cooling of the tread is going to happen quicker than the internal temp drop. This is why you still need to go and work the tyre to maintain the tread temp - you still need to get into the grip-temperature positive feedback loop on track.

Ben

[Jersey Tom]

Sure, definitely a difference between strain and heat histories. To frame that as well, there are series where you can come into the pits with tire temps exceeding 300F (149C) even after having started at ambient. Higher still while on track and running.

I'd say having heat history at that level (and along with strain) is likely to have a stronger effect than whatever blankets are typically set at.

Though I still don't think leaving tires in heater blankets indefinitely is a great thing for performance.

[ubrben]

Though I still don't think leaving tires in heater blankets indefinitely is a great thing for performance.

Agreed.

Ben

[hardingfv32]

Heat history.... I can understand that the tire loses performance relative to a constant operating temperature more history. If you had the capability of changing your operating temperature readily, could increasing the operating temperature keep the tires a their baseline performance.

In other words, because of heat history are the tires loosing performance or are their operating parameter just changing?

Brian