I was wondering how the heat cycles of a tire influence its overall grip and lifespan. I have heard much about this and I somewhat understand that when a tire is subjected to many different temperature ranges it somehow changes the rubber. I am curious what kinds of changes are happening on a chemical and physical level. Also, i just purchased the Falken Azenis 615 and am curious as to how much heat cycles come into play on this tire, or if it is more of a problem with R-compound rubber.

 

For street tires you do not need heat cycles.

But for DOT R tires it is recommended. When you heat cycle a tire you have to run it at a certain temperature range for 15-20 minutes. When you do a heat cycle it realigns the bonds in the rubber making them more sticky and last longer. I forget the exact science behind it, but it's sort of like magnatizing metal when you rub another magnet on it.

 

thanks for the input, so the cycle is actually something that helps the tire maintain its makeup. Interesting.

 

The Azenis do like to be shaved down to 4/32nds. That's where the best and stickiest part of the tire is. Although if you have already run on them most tire shaving places will not shave it because rocks and debris willl ruin their blades.

 

If you are only referring to the initial 'break-in' heat cycling, then yes its only needed for R-compounds and most R-comp distributors offer it as a free, or cheap service.

However, if you are talking about, the lifetime of a tire, I'm going to disagree with Mike here. The number and duration of heat cycles do matter, even on street tires. Every time the temperature of the tire exceeds the temperature the material can handle, further vulcanization occurs, making the tire, usually harder, less compliant, less responsive , and reducing adhesion.

Most of the 'competitive guys' in ST* classes locally felt that the RT215 Azenis didn't grip as well after some period of time, it was also noticed they didn't scream/moan/whatever you want to call it just before they let go. Refering to notes, journals, and log books, it seems that around ~150 competitive heat cycles (runs), that they went away. Usually this was between 15-20 events, 6- 8 thousand miles, and around 8 months.

To further qualify these results: this is in Texas, where air temp regularly hits 100+ for 2-3months, and surface temps easily reach 130+. None of us ran shaved tires, as these were all our street cars as well.

Of course, with the phase out of those tires, and the new batch of tires...we're all stumbling around again and don't really know the lifespan of the RT615, and the rest.

 

The thing is most DOT tires are designed for one thing and one thing only... to do their job for 1 heat cycle, meaning once you heat them up they should stay hot until your done with them or else your sacrificing traction. Anything more than 1 heat cycle and the tire will not have the same amount of grip and it will gradually become a harder compound.

 

So if were talking about Washington where temps are 65 degrees, would it be worse for the tire if it were to overheat and then cool down much further than the 100-130 degrees in texas. Would this be a more dramatic shock for the tire and therefor sacrafice even more traction?

 

I'd actually expect to see the tires 'grip' last longer or a few more cycles maybe. My thinking is your tire heat cylce temperatures wouldn't be as high as what we see. I don't know the 'critical' temperature at which the rubber's chemical properties change.

If you get a tire pyrometer you can read tire temps after leaving the course, the surface temps, record it in a small notebook, and keep track of the number of heat cycles your tires experience. Then you can tell us