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Long Term Effects Of Heat Cycles On Tires?


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Just wondering what the long term effects of the heat cycling from one school (5 sessions) would have on brand new Sport-Touring type tires (Avon 45/46).


If you look at the tires used at the Sept 3 school at Barber (Level 1), the right side rear is blu'ish/purple at the edge where chicken strips reside. That tire has only been used for commuting/mild canyon carving since the school.


What is going on with the tire?

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Tires are a lot like cookies. When they're hot, they're soft. When they cool, they harden. You can only do this so many times before the cookie (or tire for that matter) does not get soft when heated.


Street tires are different from race tires primarily in construction. A street tire has a much softer and lighter construction (carcass) than a race tire does. This is done to provide/promote heat generation.


Heat = traction However, overheating a tire is as bad as underheating it. Heat is primarily generated by flexing a tire, which happens during accelleration, braking and cornering.


Obviously a tire in a street environment experiences much less stress than it does on the track, so a street compound tire is made to flex more than a race tire. The street tire is also softer to provide a more comfortable ride.


A race tire is made to regulate heat through the stiffer construction. It allows less flex, which helps the tire from overheating.


Now that you know that... Onto your question!


The bluing you see is due to the tire getting VERY hot (perhaps overheating), and then cooling.


Some people REALLY shy away from blued tires, but I've run them in the past with comfort. Personally, right now, at the level of competition I'm at, if I had a tire that blued, I would not run it. However, that same tire would be fine for a novice racer or in a street environment. It all boils down to how hard you are going to push that tire.


In your instance, you pushed the tire obviously quite hard during the school. It cooled and now has blued. I'd really doubt that you're going to push the tire that hard again on the street, so I would believe the tire should be fine for you. You just need to ride it knowing that you don't have the amount of grip that you did at the track during the school.


Again, the bluing is just a result of the tire getting quite hot and then cooling.

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I'd check your tire pressures.


At the school the tire pressures are set to 30 front and 30 rear (if I remember correctly). OK for the track, but not ideal for the usual day-to-day street use.



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  • 4 weeks later...

I am wondering what role the suspenssion set up has in street tires heat cycle. I rode pretty hard for a while the other day. When I got off the bike I felt the back tire, and it was past warm, it was actually hot and the front was not. I run between 32 and 34 in the rear and the same in the front on Pilot Powers. I recently put on a new (to me from E-bay) shock. I noticed some wheel hop charging in and getting hard on the brakes but, the bike felt balanced and was sticking quite nicely. I guess I'd know "Bluing" if I saw it. Wouldn't I? BTW My old shock was trash and the one I got off of E-bay is like new. I went from 6 on the pre load to 3. From 1 out on the compression to 1 1/4 and 3/4 out on the rebound to 1. Stock is 3, 1 3/4, 1 3/4. I believe that suspension is everything and have been reading everything I can get on setup, and cause and effect. I don't know why it's so hard to understand but, it is.

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What role does suspension have? It's more of a tyre / suspension relationship. If the suspension is too hard then the tyre will start to flex and do the suspensions job - which is too much. The opposite is also true.


The job of suspension is, well, suspension. The job of the tyre is to do the sticky bit. Suspension should be balanced so that you get the grip you need when you need it. Suspension absorbs all of the bumps - the ups and the downs etc. so that the tyre doesn't deform whilst it's supposed to be doing the sticky thing.


Hope that clears it up.



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  • 2 weeks later...

Not to insult anyone's intelligence...


But for those among us who might not know...


There's a big difference between a tire's pressure "hot" and "cold".


Tire pressure is set while the tire is 'cold'.


Cold pressure is measured/set with the tire at ambient air/room temp in the shade.


Re: LDBANDIT finding 34 psi in his tire. If this was a 'hot' tire, the 'cold' pressure could easily be 30 psi...or less.


Also, there can be a big difference from one tire gauge to another. As with so many things, you get what you pay for. I have on occasion found a relatively accurate gauge over the counter or on the end of a hose...but usually not. Invest in a good one, and always use the same gauge. It matters.


(gauge, guage..? darn, i think i misspelled that more than once in another post. how embarassing. way past my bedtime...)


Street compound tires will wear much slower than race compound and are designed to wear off old rubber to be replaced by whats underneath. The compound is designed to last thru many heat cycles.



Bluing can be caused by more than one thing. Bottom line, it's rubber that has lost it's oil. The rubber is 'cooked'. Finding a narrow band of blue at the edge of the tire is not abnormal. It does not mean the whole tire is 'cooked'. The next time you roll it over to that point the old stuff will wear off and newer rubber exposed. Theoretically.


Regarding race compound tires...


Rubber will also react with the oxygen in the air to turn blue. Another rule of thumb: stick your thumb nail in the rubber. If it comes back, that's a good thing. If you can't dent the rubber with your fingernail...bad. Learn to read tire codes. Especially the "born on" date. Compound codes and country of origin might be nice to know as well...but, the rule is two years old. No matter what color it is.


As far as the: "You can use that tire even though I can't cause I'm faster than you" ...might be true but makes about as much sense as buying a cheap helmet. What is your head worth? And at the end of the day if you push your limits like you should... how do you know what the limit of that worn out tire is? Aren't we trying to go faster?


That being said, if the whole tire is electric blue and shredding and melting on the sides...it's cooked. Don't use it even if you are a novice. And as Dale Quarterly said to me after asking what happened when I fell down in front of him in practice at Mid-Ohio..."You can't cheat the tire man". Thanks Dale. Good advice.


But you can crash in practice. Only you know what your life is worth. What is the value of a practice in which you worry about your tires being old?



In general, a full on 'race' compound tire will give consistent race grip through about ten normal full heating and cooling cycles. Really hot tire warmers can cook a tire. That being said, the first couple cycles will be a bit better, the last two a bit less. After ten, use at your own risk. Fine for the street, maybe very careful practice if you must. I don't recommend it.


In the old days, certain brands were known for progressively and predictably losing grip over a few more races. I knew guys that ran the same tires for a half season. Turned 'em around and ran em backwards when they got worn on one side. Other brands were known to 'go off' like a switch. I used to run whatever on Friday practice, to save money and cause I wasn't gonna go that fast...and been rather surprised on heat cycle 11 when I found my self on my arse thinking, "what the ...?".


It's up to you. Just my experience.


Lastly, storing tires near an ozone source will also effectively cook a tire. Electric motors such as you find on your furnace blower for instance. In your basement where you might be tempted to or already be storing your tires. Or electric air cleaner/smoke eaters. Air conditioners, refrigerators, electric compressors in the garage...you get the idea.


That's my 346 cents... :P

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When you say 'Full Race' Compund, I take it you mean still road legal, with tread?


With my Slick tyres, I've been told by Bridgestone that I can get away with three, possibly four heat cycles, but then I should throw them away. They turn very hard and offer not alot of grip after three cycles.

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Um...yeah. I should probably add a caveat and disclaimer...


With the constantly advancing technology of tires and my own lack of 'recent' experience...as in I haven't actually purchased or ridden anything in the last several years...I should probably stick to more general and not potentially time sensitive info.


Best advice, go by your trusted tire man's info. Most of my own limited knowledge was garnered in the last century, haha. Prior to 2000. And mostly DOT treaded Supersport tires for 400/600 classes and slicks for 125 or 250 GP bikes. Mostly, Dunlop(slicks and DOT) and DOT Metzler, maybe twice on Bridgestone slicks because they were paying but I didnt like them. I can't remember why. Maybe because they didn't last? :P


When I said 'full race' compound I merely meant to distinguish from 'street' sport compound tires. Like I think were being referenced before. "Sport-Touring" I think. So...


When I switched to slicks for the GP bikes that was another level and actually having a choice of compound as opposed to whatever the tire guy gave me was another thing. I do know or used to know guys, oops, girls , um...racers that only used tires for a day, like three /four cycles, whether they had a special tire or were just so much better than me(?) or had more money I don't know. My own practice was to run fresh tires for raceday scrubbed in one practice, tho lots of guys would do just a single scrub lap + sighting lap, way more work than i wanted to do constantly switching wheels. Maybe if I was a pro or had a mechanic or trusted someone enuf to touch my bike haha.


In any case, I'm talking about slicks now (Dunlop), I would run last race tires for practice Fri/Sat up to about 8-10 cycles and never had a problem tho i could definitely tell the difference when i put on the fresh rubber Sunday. I did have the experience of running super soft comound meant for cool/smooth track on hot rough track being utterly destroyed in a day.


Again, these are light or middle weight machines not superbikes. Bottom line, like I said, if the compound is hardened or worn, don't use it. As far as how many heat cycles to run YOUR race tires, ask the tire manufacturer or distributor, preferrably one who specializes in tires and is reputable. Way back in my day haha some tracks didnt have a tire guy or just a had a dude/dudette who sold some stuff and a few tires, nothing against him/her, but these guys didnt always have the best info. For Bridgestone slicks, ask Andy. :P


PS As I said, I never enterd the lofty club that had race tires that only lasted 3 heat cycles. Being cynical, I'd be interested to know if you yourself have observed this to be true? Are they trying to sell you more tires? haha. Seriously, though I have heard of it and believe these tires exist. Just can't imagine spending the money to use them. I hope Bridgestone is sponsoring you. Do you race AMA National Superbike or World GP oops Moto GP? Chasing big purses I hope. ;)

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Ah...I see you are running a HEAVY weight bike in a National series...if they go off, they go off. If that's what everyone else is doing/using, then I guess you gotta go there. Good luck mate.

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Yeah, the fast guys at the front all run on super sticky slicks of varying compounds. Dunlops seem to be the favourite, but I prefer the Bridgestones with a higher profile, to help the bike flick a lot quicker. Most of them get through a set or two per day and at two day rounds that gets expensive! I'll be sticking to two heat cycles and then one practice session on them, possibly with some cuts in to generate extra heat, but that's it, no more fun on those. Basically, my bike really takes it out on tyres, eats them for breakfast before I even wake up! :lol:


I would love to run super-sticky race compound treaded tyres that last longer, but I simply can't afford the loss of traction that would occur, especially when braking hard up the inside of a ducati on a mission! ;)


Iam lucky in that I managed to haggle with the main tyre dealer in the paddock who deals with Bridgestone direct and I got an absolut cracker of a deal. As long as I put Bridgestone stickeres around the bike in prominant places and wear my Bridgestone baseball cap for any photos or at podium time, then they'll provide me with any compound slick tyres, fitted to the bike and hand cut for the track/conditions, all for 2/3rds of the price! Bonus! and that it still ?210GBP. ($375USD) This includes full wets as well, but they'll only really last two races, irrelevant of heat cycles or wear, they just seem to stop working?! :blink: No intermediates for me, just hand cut slicks for damp or cold conditions! Still, I have plenty of spare wheels for last minute change of mind! ;)

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$375USD and two sets a day...I don't remember things being that expensive (memory block) but maybe that explains why I'm still paying on five credit cards from last racing season.....


Of course spending several months in New Zealand didnt help the credit card bill either...


Seriously, the last BIG race i did was Laguna Seca World Superbike 98 125GP teaser class. I think I bought four sets of Dunlop slicks (2 soft, 2 super soft) in case it was cold...at special price of $180USD per set. Now I think other guys might have been paying more like $235 or there abouts, but i came home with two sets. After four days. Obviously 125gp tires are smaller hence cheaper.


Different manufacturers here used to pay "contingency money" for running stickers. If you win, place or show...there's your discount or maybe free tires if you are winning. Same for oil, fuel, chain, bodywork, brake pads, etc. Racing in America is not quite the same sort of thing as it is over the pond tho...


When i was considering doing the Euro Circuit with Rod Fee, Doug Carmichael et al, i was told you got paid if you qualified and started the race...start money I believe they called it. S**T! People in America would never believe that..but, maybe now that all us old..er folks paid the dues to bring up awareness and so many kids taking advantage of the dwindling stigma we had to deal with...just try walking into a pub dressed in leather around here when i was ..um...younger....things might change...but i doubt it. half the board of AMA was controlled by the big four manufacturers, cant imagine that's changed. If we could get thousands and thousands of spectators to come to the races maybe....


Now Ive found other things to risk my life and spend insane amounts of money on...like racing sailboats on the open ocean in a typhoon...or taking flying lessons... B) . But...I've had a hankerin' lately to 'turn a wheel in anger'. :angry:


I know there are "qualifier tires" and tires made to last a single race, my guess is most guys in the states don't have access to that stuff unless they are on AMA National Circuit and even then...not everyone. But I have no firsthand info on that. Just nasty rumours about who gets special treatment. I would never say the word fix. I've just heard rumours... :unsure:


Maybe we should discuss a little import/export business.... ;)


Must be really cool to be so close to Euro tracks and Isle of Mann. <_<


Oh well, Merry Christmas...er...Happy Holidays. :rolleyes:

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  • 2 months later...

Just for your info: my coaches use race tire take offs, so already used tires. One of the boys put over 30 school days on a front, and 19 or so on a rear. There were slicks to start with, and he for sure didn't have to go full race pace that often, but...that's still a lot of days on a tire!



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Over the past several years I've run Dunlops (208GPA), Pirellis (Supercorsa) and Metzelers (Rennsport) on an '03 ZX-6R trackday bike (not ridden on the street). I do trackdays monthly, and my pace would be mid-pack in the local CCS amatuer classes. The Pirellis and Metzelers (same tire basically) were good for 4 hard trackdays, then 1-2 at a slightly relaxed pace (started to go away after 4 days), with 4-6 sessions per day. I don't have tire warmers, so that's a few heat cycles each day. The Dunlops were good for 3 hard days, and really started to go away on the 4th, so about one day less, and went away faster.


In November, I changed to an '06 GSX-R1k, and am running Metzeler Racetecs at the moment. The first set has three days with no noticable loss of grip so far, although I changed them out for a new set, as I'm running the school at Laguna next week. I am still sorting out the new bike, so I'm not at 100% yet, but I'm running faster lap times than on my ZX-6.


Anyway, that's my experience with DOT race tires in a trackday environment. YMMV


Cheers! :D

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  • 3 weeks later...

Hmmm, I use tyre warmers and get 3 days out of Slicks. If I used super sticky road tyres, like the new Dunlop Qualifiers, I'd probably still get 3 days out of them, but might then be able to use them for a short while on the road bike.


The difference in price is not that much, so I might as well go for the Slicks and have the best grip I can get.


Just as a quick additional thought: Slicks can also perform better in the damp and cold than any super sticky road tyre. My Bridgestone guy recommends Slicks over Intermediates in the damp! Cut Slicks if conditions get worse, standing water = time to go to Full Wets.


Last Sunday (26th March) was the first round of the British Superbike Championship. In the second race it was persisting it down with rain. The guy who won the race was the only one to be using full wets. (it was raning, but it wasn't absolutly soaking wet and there was no standing water), everyone else had gambled on intermediates, just in case it got slightly dryer. Gregorio Lavilla went out on Slicks! He came fourth I believe! Held his position through the whole race! It goes to show, super sticky tyres that run hot are better than not so sticky tyres that run cooler when on a cold track. Due to the water on the track being only a surface coating, the tyre profile will push any water aside, you don't really need any tread. So go for the stickyest tyre you have!

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As it turns out, Keith went to that round, he was over there with Leon Camier. Pretty sure it was Leon's first race with a new team, and I think also new tires.



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