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Re: [ST] Tire Pressure



I see your point. I know the pressures will not increase nearly as much on the street, as the heat generated is caused by the friction from scrubbing the tires in the turns. The pressures do increase as the heat is generated, as at the three minute mark off the track, my pressures go to 33 front and 34.5 rear. I do run on a tight track, and normally do have some tire spin on most tight turn exits, so the rear does go up pretty higher than the front. I have run some DOT take offs as a temperary replacement for my worn out street tires. I can tell you from the feel factor, even after a 90 mile twisty ride in PA, the temperatures are much lower than the track bike. I do still hit enough lean to scrape my pegs regularly, but the speeds are lower, causing less scrubbing. I do not have chicken strips, but I also do not get the rubber snots from the extreme corner speeds of track use. The higher the pressure you run, the lower the temp will be. This is due to multiple factors,
 with the smaller contact patch being the biggest reason. The pressures you run on the track are between 8 and 18 psi less than you would run on a street bike. I also run about 1 psi less than most others, as I would rather pay for tires than more bodywork :) 
   
  Justin
  

Sprint ST <sprint_st@xxxxxxxxxxx> wrote:
  Justin,
Thanks for the excellent data. One of the things I want to check is center
tire temp as you vary cold pressure. While most of the this thread has
concentrated on sidewall flex as the principal factor in the temp
generation, I would think that conversion of power, thrust or whatever term
you want to call the pushing of the tire against the road to maintain or
accelerate the bike must generate heat. The problem is that there should be
multiple factors to be considered. Track is going to have much more
acceleration, braking and lean factors than most street conditions. So I
think the best thing to do is just do the experiment where I can control
some of the factors and then pick your theory to explain the results.
Rod


-----Original Message-----
From: st-bounces@xxxxxxxxxxxxxxxxxxxx
[mailto:st-bounces@xxxxxxxxxxxxxxxxxxxx] On Behalf Of JUSTIN SHREAVES
Sent: Saturday, June 24, 2006 7:46 PM
To: ST@xxxxxxxxxxxxxx
Subject: Re: [ST] Tire Pressure

My average temp on my 99 GSXR 750 on Dunlop DOT's for the rear is 128-131
center, 139-144 sides (not sidewall), and about 2-3 degrees less for the
front. This is running 28.5 rear and 30 front psi cold. Then tires are
warmed to 175. This of course is on a tight track (NHIS) and get ~3 minutes
from off the track to the stands, where temps then pressures are taken. I
would say in 3 minutes you can easily lose 5-10 degrees. Just to let you
know :) I've never checked on the street though. Maybe when this damn rain
stops I will have to research. 

Justin

Sprint ST wrote:

Jim,
I'm going to get an IR thermometer in the near future and will be testing
this stuff on the street. Since I don't ride on a track, what track guys do
is interesting but is not necessarily what applies to me. A guy on the
triumprat list did do the temp stuff on a Z6. He wound up reducing pressure
because the center was much hotter than the edges. He has 6k miles on his
current Z6 and still has tread to go. I'm at the chords at 4.8k which at
$140 per tire really interests me. (withoug actually riding with the guy, it
sounds like we are similar riders, definitely not commuters)
Rod



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