>> Allow 24-48 hours mininum time before using or don't bother
>> heatcycling at all.
>
> One aspect of heat-cycling I've never understood is the above. If the tires
> aren't good to go as soon as they cool, then there must be some bonding
> transitions still going on - that's clear. What's not clear is how. Once
> they have cooled any chemical reactions are going to be happening at a
> glacial rate compared to what goes on when they're heated up. And
> apparently those reactions DON'T take place below a critical temperature, or
> the tires would "heat-cycle" just sitting around in the garage.
>
> Have you ever heard/asked about this, Bill? It would seem to me that
> allowing the tires to cool to ambient temperature and then drenching them
> with a hose should accomplish the same thing a lot more quickly.
I'm not a chemical engineer or dumb enough to play one on the net in front
of this crowd, so here's what Jim Fogarty of BFG wrote in "Care and Feeding
of BFG R1's". For the full article, see
http://www.tirerack.com//tires/bfg/bfgr12.html
<snip>
To understand what happens in a heat cycle, let's talk about the molecules
that make up the compound. For those of you who don't remember your high
school chemistry classes, the molecules that make up polymers are long
chains of aÓtoms. To visualize this, think of a bunch of rubber bands.
Imagine that they have all been cut with a pair of scissors so that they are
not closed loops anymore. Now, throw a bunch of them into a box and shake it
up. Those represent the polymer molecules.
In addition to being highly intermingled, polymer molecules are connected,
or attracted, to each other by a variety of chemical networks. For
simplicity, we will refer to all of these networks as chemical bonds. These
bonds, or attractions, are what are important. During the manufacturing
process, these bonds form in a more-or-less disorganized way. Some of the
bonds are very short and strong. Some of them are very long and weak. The
rest of them vary between the two.
Now, when you take that tire and run it, things start to happen. The
molecules get stretched and compressed. This first causes the weaker bonds
that connect these molecules to break. When the bonds break, heat is
generated. As the heat builds and the flexing continues, more bonds break,
more heat is generated, stronger bonds break, more heat is generated, and so
on... Remember that these bonds are what connect the molecules to each
other. They give the compound its strength. When this strength is reduced,
the compound can't grip the road surface as well. It rubs off instead of
holding together. The result is less grip, more slip on the road surface,
and more heat generated. You can see that it can become a self-perpetuating
kind of thing. How fast this all occurs determines how fast the tires tend
to lose grip.
So then, what happens in a heat cycle that can improve this pretty bleak
situation? Well, actually, the situation described above is the first step
in the heat cycle process. You want to break all of those "uneven" bonds.
What happens next is where the real magic of alchemy comes into play.
After these bonds have broken, and this heat has been generated, and the
tires are finally allowed to be set aside and relax, the bonds tend to
REFORM! But now they reform to a much more uniform manner! This means that
they are more consistent in strength. Therefore, the compound becomes more
resistant to losing its strength the next time the tires are run. That
doesn't mean that you can't make the tires give up anymore. If you exceed
the limits of the compound - both mechanical and thermal - the bonds will
still break. But they will be more resistant to it because they are working
together now as equals - in parallel - instead of individually - in series.
And, given the time to relax again, they will reform again in the same
uniform manner.
Here is the most important thing to learn and remember about this process.
These bonds MUST be given ENOUGH TIME to do their magical reformation. In
the case of the R1, the tires must be allowed to relax for an absolute
minimum of 24 hrs. after that initial "break in." We sometimes tell people
to wait up to 48 hrs. to be sure. But, we really haven't seen any additional
advantage to waiting any longer than that. If you don't give the tires
enough time to reform those bonds, then you are going out on tires with a
weakened compound and their performance will show it. Understanding how this
works, and how to use it to your advantage, is important to getting the most
from your tires.
Let's talk now about the number of heat cycles you can expect out of a tire.
We've heard people talk about Brand-X or Brand-Y or Brand-Z only being good
for X number of heat cycles. We really have not seen this with the Comp T/A
R1. You should be able to expect the same performance level from the tire
after 20 heat cycles as you get after 1 - assuming, of course, that tread
wear isn't an issue. Additional heat cycles beyond the first don't make the
tire "harder." The tire can and will change over time just due to "aging."
But that is due to other influences like ultraviolet light, ozone, etc. And
that time period, with proper care, should be at least a couple of years.
So, to recap, heat cycling will improve the consistency and longevity of
your R1s. The first heat cycle is the most critical. Subsequent heat cycles
do not cause any detriment to the performance of the tire. It is still
possible to overheat heat-cycled tires. Assuming you don't do any other
permanent damage to them and give them the minimum of 24 hrs. to relax
afterwards, they should be fine for later use.
</snip>
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Bill Ozinga - webmaster@tirerack.com
Webmaster - The Tire Rack
http://www.tirerack.com
Ph.(888)541-1777 or (219)287-2345
Order your tires online!
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