Joy of 6

Have heard a lot about heat cycles, but.... Is there a definition of just what is a cycle. For instance, I did 3 track sessions on Saturday at Thunderhill and 5 on Sunday. The tires would certainly cool off over night but not too much in between track sessions. So is that 2 heat cycles or 8? I am guessing that driving to and from the track doesn't count as there is very little heat build up and high temperatures. Just got some new Toyo 888's and would like to keep score properly.

thanks,
Ed

Z Fast

Ed,

Everytime a tire reaches it operating temp and then cools, that is one heat cycle. So driving to Thill at highway speeds in warm weather will heat the tire. So that should count as one heat cycle. If your tires cool between sessions, then that is another heat cycle. How many heat cycles can you have before the tire starts to loose some performance, depends on the rubber compound. I'm not really sure about the R888. I would think that the Toyo R888 will take more heat cycles before dropping off as compared to Hoosier R6. But then again is a heat cycled out R6 any worse than a R888 in its prime? -I don't really know. From my SM series, I'm hearing the tires are good for about 8-12 heat cycles before dropping off. Does that mean they are bad? No! Just not optimal. I'm still on RA1's, so I haven't experience the R888 yet.

Your question regarding what constitutes a heat cycle, or how hot does a particuler tire have to get before that cycle will have an effect on the tire, that will depend on the tire and rubber compound. The only way to get a true measurement of heat build up in a tire is using a pyrometer with a probe. Then there is always the question of how much performance will drop off when heat cycled. Again, depends on the tire.

From my knowledge of Toyo RA1, they can really take a lot of heat cycles, and from what I heard, the rubber compound is the same as R888.

The next time we end up at the same track, remind me to bring my pryometer with the probe and we can record how much heat your tires are generating.

Tom

Z Fast

By the way, forgot to ask, how did you like the R888 compared to what you had before?

Tom

AverageVetteNut

Don't forget that a Road Racer's heat cycle isn't the same as an Autocrosser's heat cycle.

So, that's an important thing if you're going to buy used tires from someone.
Just a thought.

L98Terror

They are?

I've been told a heat cycle is a heat cycle whether it's 30 seconds or 30 minutes, the amount of rubber left will differ though

JiminVirginia

My guess is that the R888 is not soft enough (tread wear rating 100?)to heat cycle. You'll run out of rubber first.

Enjoy.

AU N EGL

A heat cycle is each time the tire is up to between 180-200*

Now you can also get very specific as to how the rubber in each tire "set" or the 1st heat cycle. Each tire most likley should be used in that same corner for the first 3-4 heat cycles.

Joy of 6

Tom,

Don't know about you, but I ALWAYS have my probe with me :o)

Am planning on attending the SM race in May, will you be there? then we can talk more. I used to have Vredstein street tires so no real comparison to the 888's

Ed

Joy of 6

Tom,

Interesting. How would an infrared sensor do?

Ed


PS. Are you coming to Thunderhill in July?

AverageVetteNut

Ok, I guess I should've clarified....
I would think that 15 laps on a road course would wear a Hoosier A6 more than 3 runs on the autocross course.

That would be closer to a heat cycle for each... but in reality depending on the temps and surface, during an autocross you might not get them up to temp to begin with while only doing one run,you'd be taking all three runs to get them good and hot.

That's what I was getting at.

I looked at a set of A6s that had '5 heat cycles' on them from a guy that did track days, and they looked like mine do after 1/2 a season autocrossing.

froggy47

I have taken temps on my 710's after a 100 mile drive to an event and they were about 5 to 10 degrees over ambient. Say 80 to 90 deg. f.
No way that is a "heat cycle".

Unless you are a professional racer and throw out dozens of sets of tires every season, it really does not matter how many heat cycles are on a tire.

Better to use a durometer and when the rubber gets "x" amount harder than when new, move the tire to your "practice tire" pile.

Take temps at events to check alignment settings (explained in other threads).

Bill Dearborn

That range of temps probably varies with the rubber compound. As for autocrossing when I check my tire temps at the exit of a course I have never found a temp over 130 degrees. Some of that may be because I use road race rubber for autocrossing.

Bill