Heat cycled.
 

Is there a way to tell if a tire is hear cycled out? Is that a thing? I don't know if my Z2's just got too hot today but my last autocross run they seemed to fall off a bit. I only ask because I have a slightly fresher set I can get mounted on before next weekend's ProSolo.

The tires in question have approximately 21 autocross runs on them and 1 track day with 4 20 minute sessions (1.6 mile course, pushed pretty hard).

I realize this is vague, but a shot in the dark for anyone who may have insight.

Thanks!

I'm also curious of this same thing. I have ZIIs as well, and while I still have a ton of tread on them, I'm wondering what are the tell tale signs of too many extreme heat cycles.

I still DD my car, but I have had about 5 HPDE events, a couple in the nice extreme heat of the midwest in summer and spring.

They heated up well at my last event at Heartland Park Topeka, and were really sticky at the end of my sessions (my tires were picking up every single bit of debris from the track and looked like I had coated them with rocks).

Would heat cycling first show as a tire that takes longer and longer to get up to temp and thus show poor traction early in a session, or would the signs be a tire that just simply never gets up to temp and seems slippery throughout a session?

I don't have any experience with Direzzas but I don't think the heat cycle is an issue with street tires (non R compounds) since the tread of the tire is the indicator of the life of the street tires (and dots on the R compounds).. even with some R compounds such as Michelin PSC, Nitto NT01 and Toyo R888 heat cycle is still not an issue and they can be street driven.. if you guys are referring to the overheat issues, did you see a bluish color around the edges? Something like this

http://i30.photobucket.com/albums/c3...20307-1655.jpg

If not you probably reach the limits of the tires or the tire pressures can be adjusted better

I ran my set of Z2s way below the wear bars before they give up the ghost. I could tell when they were gone when I was getting pretty severe push exiting turnarounds or going though slaloms on an autocross course. The tires just didn't want to "hook up" when g-forces got higher. Grip and feel on initial turn-in still felt the same, though. Lateral threshold grip was terrible....

True R compounds have a limited number of heat cycles before they start to lose grip, regardless of tread depth. High end street tires will survive many more heat cycles but you *could* go heat cycle a street tire out before it's tread is gone.

Usually it's more related to the number of times it has been heated and cooled, not how hot it got once though.

Some tires - maybe most or all tires, but I'm not a chemical engineer - have a "breaking" point of sorts where getting it too hot WILL alter the chemical structure of the rubber such that the tire will achieve heat cycle death faster.

If you daily drive your tire, you will definitely reach heat cycle death before you hit the cords. Also to contend with (on street tires) is that most manufacturers put a slightly harder base compound that you'll hit anywhere from 2/32nds to 4/32nds of tread remaining. Regardless of heat cycle health, this will reduce grip as well.

Nick the tires should start turning blueish a bit. Look at camber challenged cars the edges of the tires are bright blue due to over heating them.


Also if you think the tires are falling off. Try treating them with formula v. http://www.jegs.com/i/Formula+V/398/FORMULA+V/10002/-1
Formula V Tire Traction Treatment
Will increase life of tires
Replenishes ingredients lost to heat cycles
Allows more heat cycles than otherwise possible
Keeps tires fresh and increases racing speed on ALL surfaces
Will NOT wash off
B

I was treating them 3 times a day for about a week. Then wrap them in plastic wrap to keep them from drying out. It is a bit smelly but it will bring any tire back to life. Try not to street drive on tires that have been treated otherwise they wont work like they should when you really want them to.


also I have not run z2 but rivals rs3s z1s and r1rs on this car. I get about 200 runs out of a set. Pure autocross with street driving.

Thanks everyone for the replies. I do drive the tires on the street as well. I picked up a set of gently used RS3 V1's. The Z2's didn't have any blue on them, but fell off noticeably.

After 12,000 miles and 90 autocross runs my ZII's were toast. The grip fell off to a point they were like autocrossing on all season tires. They still had 4/32" of tread remaining but we're essentially useless unless you could build up a LOT of heat in them. On the street the traction control would kick in around any sharp corner. I did overdrive them a bit and had to spray them occasionally between runs so that may have accelerated the heat cycling out process. I replaced them with RS-3 V2's which have been phenomenal.http://i1299.photobucket.com/albums/...pszcxh2bx2.jpg

Another option is brake cleaner. Some race guys will take an old set of tires, spray it, then go qualify. Good for 2-3 laps but the tire will be ruined afterwards. Not sure how legal it is to go spray your tires with stuff in paddock before your runs, but if nobody sees you...

After I got my V2 RS3s I just decided to daily my Z2s anyway. I mostly run on concrete.

my NT05s always heatcycled before i could wear them out. most of the autox compound tires are going to do that if you arent beating the total dogshit out of the tire. if you get 15k miles out of a set its probably toast. i usually noticed them getting hard around 9k and by 12k they were just good for leaving black marks everywhere.

ZIIs dont hold up to heat like RS3s for competition, pretty common. Worse if you do track events.

But RS3s are horrible street tires, just depends on your priorities.

Are you guys referring to the overheating or heat cycling? This is the first time I am hearing a 200 rated street tire having heat cycling issues :) Heat cycling generally applies competition tires and heat cycling process is also offered for racing/competition tires. Most of the time people over heat their tires and think they are heat cycled out

Also the initial heat cycling process extends the life of the tires. FYI, many people run their NT01 to the cords ( they typically flip them on the wheel after the outer tire is worn out) and they claim the tires perform better (possibly after the tread is gone)

Here is a good read about the heat cycling if you're interested:
http://www.tyre-technology.com/index.php/heat-cycling