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Tire Heat Cycle

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extrakt0r

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Tire Heat Cycle
« on: July 11, 2005, 04:09:40 pm »
What defines a Heat Cycle? How hot does a Race Tire have to get before it Heat Cycles? If you Heat a Tire to Proper Temp, and don't use it, is that still considered a Heat Cycle?

I went to my Trailer in storage today to get something out of it, and now that I have a Tire Rack in their I had planned on just keeping my 2nd set of Race Rubberand my Rain Tires in their all the time, no need to load and unload...

But the inside of the trailer was pretty hot, along with the Tires, so I look them out and put them in my Temp Controller Garage...

My question is this. Can I leave them in their, new or used tires, either or, and how hot do they have to get before they "Heat Cycle" don't they get hot when in other storage places, or when in transport over the highways of the US of A?
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Mike Simone
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Super Dave

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Re: Tire Heat Cycle
« Reply #1 on: July 24, 2005, 06:12:18 am »
Good question, Mike.

I'm not sure there is a great answer.

I know in World Supersport, they would heat some tires to like 200 degrees for several hours to cycle them "once", and race on them.

In the winter months, I store my tires down stairs in the basement out of the sun.

The tire has an operating temperature, probably 140 to 160 degrees, and I would guess that the inside of a trailer certainly might get that warm.  How much it actually affects the tire is potentially not measurable.  

The one thing that might be good for it is the duration of the heating and the cooling.  It's not a huge shock like heating it on a tire warmer, then racing on it where it might get warmer, and then the temperature comes crashing down after the race.
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Super Dave

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ekraft84

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Re: Tire Heat Cycle
« Reply #2 on: July 26, 2005, 07:02:58 am »
I wouldn't think you could go through a "heat cycle" by having your tires in the sun, or in a hot trailer.  My two cents would be that the tires have to get up to a higher temp - either via a warmer or by being out on the track to classify as a heat cycle.

With that said though, I keep my tires in the basement / heated garage over the winter as well.
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Eddie Kraft - #48
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Motorace

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Re: Tire Heat Cycle
« Reply #3 on: October 06, 2005, 03:00:18 pm »
What causes a race tire to age is use. You are dealing with a piece of rubber that was designed with a very short lifespan - as long as you store it properly it will last.

However, doing lots of laps at a very aggressive pace naturally takes life out of the tire. There will be one lap in which the tire says " no more". And after that, you never get that time back again.

Heat cycles don't cause this. Use and wear cause this.

Running a DOT soft in the August heat at Jennings may only subject the tire to two "heat cycles" before it is shredded. What killed its performance? It only had two sessions on it....

We had this issue in LRRS with riders wrapping tires in warmers all day trying to keep tires at 135F or so all day long to lessen its "heat cycles". This does NOTHING to extend life of a slick or DOT.

A Michelin 1246A front or Pilot Power PR5 Race only has so much use in it at a certain level. And lessening "heat cycles" does nothing to extend nor decrease this.
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Dave Pawlikowski
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whitey_1964

Re: Tire Heat Cycle
« Reply #4 on: October 09, 2005, 12:47:15 pm »
Heat cycles are commonly understood to be any process which causes a tire to heat to its normal operating temperature (or above), and then allowed to cool again back to ambient temperature.  This can be done several ways.... oven, tire warmers, track time scrubbing the tires in, etc.  The important thing to note is that the tire does NOT have to spin a lap in order to go through a so-called heat cycle.

Taking a tire through a heat cycle, or heating any rubber for that matter, effects the chemical compounds that are used in making the rubber component, and causes the rubber to cure further (ie: become harder). The rate at which this process causes chemical change depends on the compounds used to make the part, the amount of heat applied, and the duration.

With motorcycle tires, generally what most people notice (if the tires haven't worn out first) is the blue-purple ring that forms on the outsides of the tire tread wall. These colors are formed when the oil used to make the tires is forced out of the compound by heat and pressure. As the oil leaches out of the compound, the rubber becomes harder. While this is good for tire wear, it also causes the tire to be less flexible, and provides less traction (generally considered very bad in motorcycle racing). Note that this discoloration does not have to be present/apparent. You could still have a tire which has cured a great deal over new, becoming quite a bit harder, without this tell-tale coloring.

Post curing caused by heat cycles (at least with regard to race tires) is a bit of a delicate balance. A little extra curing due to heat increases tire life a bit by making the tire slightly harder. Too much curing though and you have a tire that becomes too hard to provide the traction you want, regardless of whether the tire is worn out or not.

Heating a tire above ambient, even if not done up to or above the normal operating temperature for the tire, (such as storing it in a hot trailer) still may cause some additional slight post curing of the rubber over time though. It really depends on how hot it is in the area they are stored.
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endoracing

Re: Tire Heat Cycle
« Reply #5 on: December 04, 2005, 02:23:02 pm »
Hrmm, so then the only advantage of tire warmers is to have the tires up to temperature as soon as you get out on the track? nothing to extend the life?

it sounds like keeping the tires hot longer between track day sessions just means they are curing longer inside the warmers, where if you just let them cool instead they would be better off. I can see why in racing you would want that first lap to count, but at a regular track day it doesnt seem beneficial.

is this the case ? just curious, maybe I'll stop using my warmers at track days...
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ekraft84

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Re: Tire Heat Cycle
« Reply #6 on: December 04, 2005, 03:19:45 pm »
Quote
Hrmm, so then the only advantage of tire warmers is to have the tires up to temperature as soon as you get out on the track? nothing to extend the life?

it sounds like keeping the tires hot longer between track day sessions just means they are curing longer inside the warmers, where if you just let them cool instead they would be better off. I can see why in racing you would want that first lap to count, but at a regular track day it doesnt seem beneficial.

is this the case ? just curious, maybe I'll stop using my warmers at track days...


Warmers should still help extend the life of your tires.  The process of gradually cooling them down with the warmers (rather then just putting them on to heat up) is supposed to contribute to that.  
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Eddie Kraft - #48
Witchkraft Racing
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