Couple of Q's on heat cycling tires.
02-13-2003, 05:49 AM
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Couple of Q's on heat cycling tires.
What is it? Why do it? What's the benefit? What do you do to heat cycle them? Do it only once for new tires? Is it primarily for track use or for track and street (regular driving) use? Used for track rated tires only? TIA...have seen this lingo thrown around a few times, but never really grasped the concept to fully understand it.
02-13-2003, 06:32 AM
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Heat cycles...
Brand new race tires are considered to be "green", and need to be brought up to operating temperature under mechanical loads to finally "cure". Just as glue cures, tire rubber cures by changing it's molecular structure. The tire guys explain it the process to be the rubber compounds forming long molecular chains from shorter chains.
Once a tire had been thru an initial 'heat cycle" it is thought to be a more durable piece. A new tire might begin to chunk and cord in 2-3 hours of track time under load, while a "heat cycled" tire will go hours and hours and hours.
Street tire compounds are dramatically different from race rubber. By their nature, they don't need any initial "heat cycling". Race rubber does need it.
How to do it ? Simple - mount up your new race rubber, correctly inflate them and take them out on the track. You're trying to get them up to operating temperature (180-210 deg. F.) and hold them there for a short while. It depends on your driving style, the track and air temp, your chassis and your speed thru corners. It might take you 4 laps, it might take you 8-10 laps. We'll take new Kumho's and Toyo's and run them hard till they start to feel "greasy". Then park the car, remove the tires and put them someplace cool for 24-48 hours. This "rest period" is critical, as the chemical changes in the tire compound occur then.
Every time you take a tire out on track, you're giving it an additional "heat cycle". Some race tires will go 15-20 heat cycles without a major noticable change in grip, others will only go 3-4 cycles before you see a noticeable change in grip (up to a couple of seconds a lap). The tire will look perfectly good, but won't have any stick. The stickiest of the DOT race tires, like Goodyear and Hoosier, seem to "go off" fastest.
Another little missive from the College of Rubber at Trained Seals University...
Once a tire had been thru an initial 'heat cycle" it is thought to be a more durable piece. A new tire might begin to chunk and cord in 2-3 hours of track time under load, while a "heat cycled" tire will go hours and hours and hours.
Street tire compounds are dramatically different from race rubber. By their nature, they don't need any initial "heat cycling". Race rubber does need it.
How to do it ? Simple - mount up your new race rubber, correctly inflate them and take them out on the track. You're trying to get them up to operating temperature (180-210 deg. F.) and hold them there for a short while. It depends on your driving style, the track and air temp, your chassis and your speed thru corners. It might take you 4 laps, it might take you 8-10 laps. We'll take new Kumho's and Toyo's and run them hard till they start to feel "greasy". Then park the car, remove the tires and put them someplace cool for 24-48 hours. This "rest period" is critical, as the chemical changes in the tire compound occur then.
Every time you take a tire out on track, you're giving it an additional "heat cycle". Some race tires will go 15-20 heat cycles without a major noticable change in grip, others will only go 3-4 cycles before you see a noticeable change in grip (up to a couple of seconds a lap). The tire will look perfectly good, but won't have any stick. The stickiest of the DOT race tires, like Goodyear and Hoosier, seem to "go off" fastest.
Another little missive from the College of Rubber at Trained Seals University...
02-13-2003, 06:43 AM
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thanks. that really was a good explanation.
You mentioned the Goodyear's and Hoosier's "go off" fastest, does that mean they heat cycle quicker --> a good thing?
Should I consider the heat cycle aspect when purchasing new track tires? Or is it something I should only concern myself with once I have the tires and am using them?
Should I consider the heat cycle aspect when purchasing new track tires? Or is it something I should only concern myself with once I have the tires and am using them?
02-13-2003, 08:39 AM
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Be careful ! Not the same as on the car....
I had Tirerack heat cycle my tires for a a few years then did it myself and found a huge difference.
Example: When TR did them on their machine a set of Hoosiers would last under two days at Summit Point on my BMW M5. This consisted of 6-8 heat cycles (track sessions), 20 minutes each. By the 9th or 10th heat cycle my lap times would drop nearly 1 1/2 to 2 seconds and the tires would feel like they had no grip.
When I did them as John described (on my car) I could get an extra 4 cycles out of them on average. This meant an extra day at the track. What struck me most was not the extra heat cycles but the fact that the lap times dropped off less sudden than when TR did them. Instead of going from a good cycle to a completely bad cycle it was less of a loss of grip.
I can't imagine how that machine they use could ever simulate hard cornering forces that car goes through.
Regards,
Jon
88 M5
95 F355 C
Example: When TR did them on their machine a set of Hoosiers would last under two days at Summit Point on my BMW M5. This consisted of 6-8 heat cycles (track sessions), 20 minutes each. By the 9th or 10th heat cycle my lap times would drop nearly 1 1/2 to 2 seconds and the tires would feel like they had no grip.
When I did them as John described (on my car) I could get an extra 4 cycles out of them on average. This meant an extra day at the track. What struck me most was not the extra heat cycles but the fact that the lap times dropped off less sudden than when TR did them. Instead of going from a good cycle to a completely bad cycle it was less of a loss of grip.
I can't imagine how that machine they use could ever simulate hard cornering forces that car goes through.
Regards,
Jon
88 M5
95 F355 C
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02-13-2003, 09:52 AM
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John, what is the best way to heat cycle before you get to the track?
For those of us without multiple sets of track wheels... what's the best way to heat cycle on public roads? can you get the tires hot enough on the highway?
02-13-2003, 12:22 PM
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You can heat-cycle the tires yourself if you have a local track you can just do a 20minutes at.
Or when you are hardcore enough and have more than one set of track tires/wheels,
you go to your track day with already heat-cycled tires , and your new set.
first session is done with your new set to heat cycle them. remove. put on heat-cycled tires for entire event
and so on so forth
you go to your track day with already heat-cycled tires , and your new set.
first session is done with your new set to heat cycle them. remove. put on heat-cycled tires for entire event
and so on so forth
02-14-2003, 07:21 PM
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40 Heat Cycles on Slicks - LOL
DJ and I went to Thunderhill last week. The slicks I ran had 40+ heat cycles on them. DJ said I was the only car that appeared to be driving in the rain (of course the track was dry), but I got my moneys worth out of the steering wheel.
DJ had the good tires - only 30 cycles. We wanted to practice, but did not want to tip our hand as to what kind of lap times we could really do.
Note to self - don't try to run any serious races at 40 heat cycles.
DJ had the good tires - only 30 cycles. We wanted to practice, but did not want to tip our hand as to what kind of lap times we could really do.
Note to self - don't try to run any serious races at 40 heat cycles.