Tyres degrading and falling off the cliff

[ubrben]

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

It depends on whether we're just talking about heating the tyre or a used tyre generating less temp because the tread is thinner.

Heat generally will cause the rubber to harden because more cross links are created. A worn tyre with a thinner tread will also have "harder" rubber, but the fact that it's thinner means less shear deflection and energy input into the tyre.

You can't chose the operating temperature and chose to increase it. It will go down as the rubber gets thinner and harder through use.

Ben

[munks]

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

I vote for something in between. After all, the grooves from a few years ago were 2.5mm deep, and there was still tread when those got worn down (yeah, I realize that some of the surface probably just got rearranged rather than literally worn off). And it seems a bit unlikely to me that a Pirelli with only 0.5mm of tread could survive even a single lockup, especially given how many kilograms of marbles they picked up at China between sessions.

EDIT: According to http://www.formula1blog.com/2011/04/14/ ... hinese-gp/, the average Pirelli tire will shed about 1.5kg (the tire starts at ~8.5kg). Given a circumference of 2.07m and width of 0.35m, and a rubber density of approximately 1.0 g/cm^3 (conservative value; I have some reason to believe it's a little less than that), that works out to a worn depth of just over 2mm. Technically, of course, this is indeed closer to 0.5mm than 0.5cm, as you said.

[marcush.]

So that is one reason for cleaning the wheels and tyres---you can derive the exact amount of rubber worn of the tread.(taking weights of the sticker tyre shod wheel before and than trace the weight over the weekend )...every little information counts.....

[Dragonfly]

AFAIK slick tyres are manufactured with small "wells" (4-5 mm diameter) on the protector surface and their depth can be measured with a gauge directly givin indication of wear and remaining depth.

[strad]

AFAIK slick tyres are manufactured with small "wells" (4-5 mm diameter) on the protector surface and their depth can be measured with a gauge directly givin indication of wear and remaining depth.

Yep...once they scrape the crap off them

[DaveKillens]

There is also the issue of "Heat Cycles". That too has a profound effect on a tire. If, for instance, a tire was used on Friday practiced, then allowed to cool to ambient temperatures, it would have experienced one complete heat cycle. But maybe it's better to cover it with a warmer as soon as it comes off the car, and keep that tire at an elevated temperature until it is required again, even for the race. That way, you avoid having the tire going through a complete heat cycle, when it's better to just keep it warm for 48 or 72 hours.

[marcush.]

I have spent hours if not days amassing data of the tyres my drivers used .Some proved useful some less so.
My idea of it all:
The tyre is not really cured when you get it ..So the curing process is interupted at best so to speak when you collect the black gold at the tyre supplier.
So practise and race are two more curing stages along the way ...So to get a lap time you don´t want to cook the tyres too much before your qualy attempt ,but you also don´t want to overstress them by leaning too much on them too early .F€or the race proper maybe you don´t really need ultimate grip for one lap but a bit of stamina .....so maybe it´s worth considering to deliberately heat them up a bit more at somewhat higher temps for a defined time to get them a bit more cured without taking the rubber off ...so maybe 2 hours @110°C ,anyone?

[Jersey Tom]

But maybe it's better to cover it with a warmer as soon as it comes off the car, and keep that tire at an elevated temperature until it is required again, even for the race. That way, you avoid having the tire going through a complete heat cycle, when it's better to just keep it warm for 48 or 72 hours.

Not sure I agree with this line of reasoning. Admittedly there isn't much opportunity to chase down such things in a controlled manner. But to me, a heat cycle is just heat history. Temperature goes up.. stays there a while.. goes down. Area under the curve is your heat history. You add history (and with it change x-links etc) with either a lot of these cycles, or by just holding at elevated temperature indefinitely. Hence my earlier comment that I don't think such a thing would necessarily be good for performance.

The tyre is not really cured when you get it ..So the curing process is interupted at best so to speak when you collect the black gold at the tyre supplier.

Not sure I agree with this either. On what are you basing the "not really cured" bit? Or how are you defining "cured." ? I'd argue that most race rubber is actually fairly well "cured" or stable when you get it, relative to green (uncured) rubber anyway. Otherwise you'd go through too much of a change in your early running or the thing just wouldn't have the guts to survive. I'd speculate it would just fall apart to crap.

Or put it this way.. why would a tire manufacturer produce an undercured (let's call it "not yet stabilized") "hard" tread when you could just make a stabilized soft tread?

Now admittedly the process will certainly continue once you take possession of the thing and start running around on it. But I'm just not comfortable with saying that race treads are typically "undercured" ... even though such theories have come up in literature. Either way Ben probably has a better feel for this aspect of things than I.

For the race proper maybe you don´t really need ultimate grip for one lap but a bit of stamina .....so maybe it´s worth considering to deliberately heat them up a bit more at somewhat higher temps for a defined time to get them a bit more cured without taking the rubber off ...so maybe 2 hours @110°C ,anyone?

Such is the premise behind heat cycling tires before a race. Trade some peak performance for longevity.

[marcush.]

hm ..I ´m coming from the line of thought of all resin curing processes ...and there you learn that curing of resins does not involve all the base incredients at all and in effect the polymerisation just goes on and on over time ....at a very slow rate ,yes,but still there is something going.
Put your brand new tyre in the shelf and tell me its the same after storing it 1,2,3 years and do the same when you have run it a few laps .....yopu may call it history I call it curing...but in effect i´m not sure if we are just debating words.

[strad]

JT..Maybe DaveKillens touched on something though..Perhaps it would be better to slowly cool the tires in a controlled manner rather than just letting them cool quickly to ambient..sorta like seasoning in metal ...or...maybe it's better to throw them into an ice bath...hmmmmmmmmmm

[ubrben]

hm ..I ´m coming from the line of thought of all resin curing processes ...and there you learn that curing of resins does not involve all the base incredients at all and in effect the polymerisation just goes on and on over time ....at a very slow rate ,yes,but still there is something going.
Put your brand new tyre in the shelf and tell me its the same after storing it 1,2,3 years and do the same when you have run it a few laps .....yopu may call it history I call it curing...but in effect i´m not sure if we are just debating words.

If you're storing them for three years, chances are any free oil in the tyre may leach out into the atomosphere.

I don't think you, JT or I are disagreeing too much. You'd be right to say that a used tyre will have cured more. I've seen some very old data on used tyres where the cross-link density - i.e. how many sulphur bridges there were between the rubber chains had indeed gone up. But by the same token I wouldn't say the tyre is "under-cured" when you get it. If that were true scrubbing tyres would be essential for all tyres, which I don't believe it is.

Pre-scrubbing tyres is sensible if you compounds that are too soft for what you need and you want them to be a little harder. However if your compound is the right strength for your application all you're doing is loosing performance by scrubbing tyres. The release agent will come off inside a lap, and certainly by the time you've got the pressures in.

Ben