Scrubbing in tires/heat cycles

[rotax81]

thats a new 1 on me,where have you got that from? and i have to say i'm higher than highly sceptical on that,not that i'm calling you liar or owt 

i cant remember where i got it from, 3 or 4 years ago was a long time     i will try and dig it up 

[leanittiluloseit]

i cant remember where i got it from, 3 or 4 years ago was a long time     i will try and dig it up 

Yeah I be interested to hear that. Else why would everyone always refer to them by "compound"??

[rotax81]

i couldnt understand it either. perhaps it was a load of old baloney because i understood the rubber had altered chemical ingredients to reach its goal.

im still looking for the info 

[scooby]

well from experience of changng lots of tyres,the only tyre that has noticable difference  in the side walls are thew N-Tecs,they are a lot stiffer than the corsa's+racetecs,i think michelins are silmilar and are a little stiffer.i changed a set of pirreli late last yr (sc0 for a 2) and never noticed any difference in the walls.

plus a lot of tyres now are multi compound,and on my N-tecs that are on at present there are distinct lines between the 3 different compounds,front and rear.

i think that old age thing is playing tricks on your mind 

[Kowalski]

N-tecs and Michelins must definately definately have stiffer sidewalls on the rears 'cause they run lower pressures than others . Regarding Rotax's post though , I think ya must have read on here about the 0 compounds having softer sidewalls as well as the rubber being softer , there was a post a while back about them and I think it was MC101 who pointed it out 

[leanittiluloseit]

It would make sense if the compounds where different, else I couldnt explain the massive difference in performance depending on ambient temp, Like I said with sc2`s they were "ok" even when it was pretty damn cold 

[Kowalski]

it was a load of old baloney

 

 

[mc101]

Pirelli and Metzler use the same material on the surface of the tyre but they are cured for different times based on the target tyre.

K01/Sc0 - Front: Much Softer construction and softest compound , Rear: Much Softer construction – Softest compound
K1/Sc1 – Front: Construction firmer that the 0 and softer than the 2, Rear: Same as the SC2/K2
K2/Sc2 – Front and Rear : Stiffest construction / compounds harder (cured longer)

The zero is noticeably softer in construction terms whereas the difference between the 1-3 compounds is comparatively “small”.

[leanittiluloseit]

Pirelli and Metzler use the same material on the surface of the tyre but they are cured for different times based on the target tyre.

K01/Sc0 - Front: Much Softer construction and softest compound , Rear: Much Softer construction – Softest compound
K1/Sc1 – Front: Construction firmer that the 0 and softer than the 2, Rear: Same as the SC2/K2
K2/Sc2 – Front and Rear : Stiffest construction / compounds harder (cured longer)

The zero is noticeably softer in construction terms whereas the difference between the 1-3 compounds is comparatively “small”.

So with the softer construction the SC0 would be better running a lower cold presure to aloow for greater flex and heat buildup I assume? 

[rotax81]

So with the softer construction the SC0 would be better running a lower cold presure to aloow for greater flex and heat buildup I assume?

its an odd thing this pressure business.

for the whole tyre to warm you need low pressures, however the actual contact patch will be colder. its hard to explain but in kart racing we used to up the pressures to heat the contacting rubber. normal summer pressures were 11psi to 12psi, this went up much higher on cold/damp days. same with the wets... pissing down they were around 50psi, wet/damp were a mere 20psi.  something to do with the rubber squashing on the contact patch, heating the tyre.

[leanittiluloseit]

its an odd thing this pressure business.

for the whole tyre to warm you need low pressures, however the actual contact patch will be colder. its hard to explain but in kart racing we used to up the pressures to heat the contacting rubber. normal summer pressures were 11psi to 12psi, this went up much higher on cold/damp days. same with the wets... pissing down they were around 50psi, wet/damp were a mere 20psi.  something to do with the rubber squashing on the contact patch, heating the tyre.

I mean providing your using it at ideal riding weather. ie lower pressure than a standard SC in the same conditions..

I think the idea behind higher pressures generally in the cold is that the tire will expand less with heat, so for the tire to sustain its structure and shape, you need a higher starting pressure. So say on a hot day the tire will expand 12 degrees (numbers im pulling from the air), and the tire holds the right structure at 50, you start with a ambient pressure of 38 degrees. But if the tires only expanded 4 degrees on a colder day, then you would start with 46, giiving you the same desired 50 when warm.
 Thats how I understand it anyways.

But then you get into a carcass with more flex (presumably  to maximise contact patch?? ) will generate more heat through flex (i`d imagine) making me wonder about a lower starting pressure! phew !