Re: [ST] heat cycles

[chuck boatwright <dirac@xxxxxxxxxxx>]

bare wrote:

>Heat cycles are critical only to racing tires. Street rubber is formulated
>not to have the issue. 
>

While in principle I agree with you, my experience is different.  I have 
run a set of rubber back to back at two of the hottest weekends 
imaginable at buttonwillow raceway then thunderhill.  both weekends the 
temperature was over 100.  I was working on my "endurance" and was doing 
about 45 minutes on / 20-30 minutes off.  [checking notes....  I did 437 
laps in 4 days, and..  consumed 5 gallons of water, 8 quarts of 
pedialyte, several pounds of bananas]  These tires were still ok for 2 
more sprint races, but were retired because I ran out of rubber on the 
left side.  The tires didn't really go off.  I probably could have gone 
faster on new tires in the sprint race, but I am a mid packer, and the 
half a second a lap faster, due to the confidence of having new tires 
wouldn't have made a difference in points.  

I have had tires that started to go off after 2 race weekends and a  2 
session track day [less than 200 laps on these tires, but these tires 
were a year out of manufacture when I put them on].  The ambient 
temperatures were much lower, and the change in tire temperature was 
fairly signifcant (I pit with a geek who has one of these 
http://www.quickcar.net/tire_mgmt/mini_pyro.html ) -- I have 2 years of 
data points on tires (mostly me330/550 and dunlop K591s).  These _are_ 
street compound tires.  

Facts:  Street tires do start to go off with heat cycles.  much more so 
than with laps [miles].

I will stand by this summary:  The more complete heat cycles you put in 
a tire, the more the rubber starts to change from sticky to less sticky. 
 Riding to the store, going to work or even enjoying a couple quick 
loops of your local cloverleaf highway interchange (when that's the only 
corners around, they are better than no corners) probably won't 
constitute a real heat cycle.

>This is why it is bad practice to use used race tires
>on the street. 
>
bare -- please note that I mentioned that I race on bias ply tires (me 
330/550s).  so my comments are more applicable to street riding that 
using a race tire

I ain't flamin' ya, just makin' the facts clear.  there is too much 
misunderstanding, BS and crap about tires on the internet..  but, then 
again, it is winter, and cold, and rainy / snowy.  We should be morphing 
this thread into an oil thread pretty soon.  heh heh heh

And for those of you who are still with me, and are wondering, how the 
hell does he get 400 laps on a set of tires, I race a gutless wonder.. 
 a ground shaking 30.8 hp, 15.4 ft/lb torque, put the fear of the dark 
into you 1989 vtr 250.

So..  run manufacturers tire pressures.  don't put 208 As on a street 
bike,  don't ride on the sidewalk..  etc... hrmmmmmm  should I mention 
100 octane race gas <ducks>?


- --chuck
02 st

p.s.  [humble confession]  I do put my old race tires on my street VTR..  



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