"Michael K.S." <MichaelKS@image.dk> wrote in message
news:5vqhqt4vdrokgq04ovgq8lb5656v15vjg0@4ax.com...
> Jeg søger noget info,i form af artikler i blade eller links hvor
> spørgsmålet er behandlet.Altså hvor mange heatcycles et
> racedæk/gadedæk (brugt til race) egentlig kan klare før dækkets
> compound er signikant ændret og grip væsentlig nedsat.
>
> Både specifik info for fabrikater,men også generel info søges....
Det er neppe noen helt klar regel omkring dette, men nenenfor gjengir jeg en
post fra Steve Brubaker fra Dunlop. Min personlige erfaring, er at et typisk
racedekk klarer temmelig mange oppvarminger før man merker en markant
reduksjon i grepet. De dekk jeg benytter på Ringen, holder typisk til 35-50
runder ved normal utendørstemperatur. Jeg kjører sjeldent mere enn 3 runder
ad gangen, og i tillegg benyttes maskinen til en del småkjørsel. Det er
først når dekkene er slitt 70% ned på sidene, at jeg kan konstatere at
grepet er blitt markant dårligere. For de fleste "normale" førere, er det
dermed ikke noe man behøver bekymre seg om, ihvertfall ikke så lenge
racedekkene benyttes på bane. Til gatebruk, med gjentatte oppvarminger, kan
det nok sikkert forholde seg annerledes.
JS
--------
On the question of heat cycles:
Yes tires tend to get less grip with heat cycles. But street tires have
been compounded to be very resilient to heat cycling and have a
very small amount of grip loss from new to worn. Now is a heat cycled race
tire as grippy as a new street tire? Well that is like saying is
435,876=435,874. the answer is NO. But they are very close. But for all
practical purposes they are about the same. In some cases more, and other
less, but the difference is small.
Basic datums:
1) Given the same compound, tires with thick tread have more grip than if
they were molded with thin tread. So if a tire
was molded with 2mm of tread, it would not grip as good as a tire molded
with 4mm of tread (given the compound and construction was the same).
2) Thicker tread tires run hotter, thin tread tires run cooler.
So yes, tires do heat cycle. And yes the compound of race tires tends to
drop off more than street tires, after the first couple of heat cycles.
But an important and more contributing factor, to the heat cycle issue, is
how worn the tire is. If the tire is a bit worn out it will tend to have
less grip. This is a factor not of the compound itself, but of the
thickness of the compound. The solution is a new tire with new thick tread.
But as in my last post. If you are having grip problems riding on the
street, you need to be on a racetrack!!! The issue of heat cycling is a
race track issue. Not a street tire issue.
TIRE PRESSURE:
All tire pressures are checked cold!
Street use:
OEM tires, run what the manual says Replacement tires, check with the
tire manufacturer for their recommended tire
pressure. For Dunlop's check
http://www.dunloptire.com/cycle/fitment.html
Racing use:
Check with the tire manufacture's trackside rep for recommended pressures
for that track.
The pressures are checked cold and then left alone for your ride. There is
no other magic or special pressure you can do to get more out
of your tires. Sometimes riders like to check their tires hot and try to
make the hot pressure 10% more than the cold pressure. This is simply
stupid! In fact you are probably changing the bikes setup and stability for
the worse.
The idea that the hot and cold pressures are related in such a simple
manner, and then to change the pressure based on one factor (hot
temp/cold temp) is very short sighted. Factually the things that make a
tire go up in pressure when hot, are...
1) How fast you corner/ , lap times
2) Bike+rider weight
3) Bike horsepower and how the rider uses it
4) The newness or oldness of the tire (tread thick or thin)
5) Humidity of the air in the tire
Now frankly the tire temperatures on the street are not even close to those
on the track. So hot pressures are not an issue in street riding.
As a rule, The hot pressure is simply the hot pressure. It does not mean
change anything. It means its the hot pressure and has no other
significance than that. If you go faster the pressure will be more. The
increased pressure does not mean "raise the pressure", because this will
make the bike handle different and probably result in less overall grip.
After you check your cold tire temp, put the gauge in the bottom drawer of
you toolbox and close it!
--
Steve Brubaker, President, Race Tire Service Inc.
Dunlop Motorcycle Roadrace Tire Distributor Eastern US
Order 800-772-TIRE, Tech Info 615-641-2234, Fax 615-641-8959