[ausgeflippt951]

Charlie, I disagree -- I don't see how an alignment alone would cause this.


From a materials perspective, most polymers are either thermoplastic or thermosetting. Thermoplastic means that once a polymer is subjected to heat and cooled back down, it retains its original pre-heat molecular structure. Wax, for example, is a thermoplastic -- it's exactly the same after you heat it up (even melt it), and you can do so again and again and again and again...Other examples are ABS, Polycarbonate, or Polyethylene.

Thermosets are the opposite -- once subjected to heat and subsequently cooled to ambient temps, they do NOT retain their original chemical/molecular structure. Most epoxies are like this, in that the heat forms irreversible bonds that cannot be un-done with by simply removing said heat.


There's other stuff going on here, but you get the idea.


As you may have the inkling, rubbers tend to be thermoplastic. How else would we be able to get them hot and sticky over and over again?

That said, funny stuff takes place when a polymer is subjected to extreme temps (on the cold side, below the glass transition temp, and on the hot side, above the melting point).



So how this relates to chunking: chunking is usually phenomenon that occurs when the tire is unable to be malleable ("flexible") enough to handle the required displacive lode (usually from cornering) and therefore becomes brittle and fractures. But how did the tire get this way in the first place? It has to do with the chemical makeup of the tire. Remember how I said that rubbers tend to be thermoplastic? Well, not many polymers in the world are 100% thermoplastic, and the more complex the monomer chain, the more nuanced the material properties.


So, as the tire is heated and cooled, heated and cooled, this heat cycling DOES take an effect on the tire -- we all know this. The chemistry of the tire molecularly changes! The primary advantage to race tires -- and where street tires fall short -- is that they are capable of withstanding greater differentials in heating- and cooling (and are often more capable of withstanding more heat cycles, period) than their street counterparts.



So for your PS2's, as you push them harder and harder, they will be subjected to heat cycles. What will REALLY increase this heat cycling effect is when you're very HARD on the tires within a short timespan, so as to limit the tire's ability to dissipate heat (rubber is a very poor heat conductor, meaning it takes a while to dissipate). This is often manifested in harsher driving styles, whereas the smoother drivers do not localize the heat application, thereby keeping the heat cycle more under control.

[BlackTalon]

Chunking can indicate any or all of the above... The tire does not know if the lateral forces and heat build-up are due to awesome droving on the edge or slower -- but rougher -- droving.

Then again, I don't think I ever took the time to actually ask a tire what it was feeling... Maybe it's time to for me to make the switch from Spike to Bravo, and explore the more sensitive side of things...

[ausgeflippt951]

Forgot to close the explanation: as the tire experiences more and more heat cycles, it steadily turns less thermoplastic and MORE thermosetting. As it gets thermosetting, it reverts less to its original molecular makeup at ambient temperature and becomes more brittle.


This is the exact same reason why old tires crack, though this phase changing has also been "enhanced" by UV degradation, as well as heat.

[CanAm]

Originally Posted by John Clay

I don't see where "sloppy" has anything to do with it. You could be smooth, consistent, and fast everywhere, but just be operating at a slip angle that is too much for the tire to handle and it will overheat. You could also be sloppy, bad line, fast in some turns/slow in others, and also be overheating your tires. Just because you are overdriving your equipment doesn't equate to sloppy.

Good clarification. I was sloppy in my use of the term 'sloppy'.

[BlackTalon]

Originally Posted by ausgeflippt951

chunking is usually phenomenon that occurs when the tire is unable to be malleable ("flexible") enough to handle the required displacive lode (usually from cornering) and therefore becomes brittle and fractures.

????

Because it is not flexible enough it BECOMES brittle ???

I think I need to go back and study some of my old ESM texts...

[CanAm]

^ Jeez Collin, Honary PhD in materials science for you, if you don't already have a PhD in it.

[Charlie Stylianos]

Originally Posted by ausgeflippt951

Charlie, I disagree -- I don't see how an alignment alone would cause this.

I wasn't suggesting that alignment alone was the culprit......the other possibilities/remedies have already been suggested. My point was if the OP wants to continue on with his current droving habits on street tires, then possibly some additional suspension/alignment changes could help this 'chunking' issue of which he speaks.

[CanAm]

Originally Posted by Charlie Stylianos

I wasn't suggesting that alignment alone was the culprit......the other possibilities/remedies have already been suggested. My point was if the OP wants to continue on with his current droving habits on street tires, then possibly some additional suspension/alignment changes could help this 'chunking' issue of which he speaks.

I haven't had significant chunking with my PS2s. The topic of chunking came up in relation to being a possible indicator of when to switch from street to track tires.

BTW, did have a realignment done for the Cayman R, and it does seem to have helped overall.

[Charlie Stylianos]

good lord....then this is really a non-issue......

[John Clay]

Originally Posted by Irfan

I haven't had significant chunking with my PS2s.