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PostPosted: Tue Mar 11, 2014 9:31 pm 
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Tubbie Guru

Joined: Tue May 03, 2005 2:20 am
Posts: 5796
Location: Belgium
Hi,

Quote:
This is pretty much what I'm asking. Is there anything inherent in the handmade procedure that a vulcanised tyre can not achieve? Got conflicting opinions so far. And I don't mean exceeding just in any one characteristic, but with the goal of balancing grip, puncture protection and rolling resistance.


The main difference between the two is that the handmade procedure allows you to use any tread available, natural rubber (produced from latex) or synthetic. All rubber is vulcanised or it wouldn't be of any practical use for a tyre BTW.
The vulcanisation process we are referring to is the process that allows two different compounds to become permanently attached. I.e. multi-compound tyres where a different rubber is used for tread and casing.
In order to achieve this a chemical process is re-used (vulcanisation) so the various rubber compounds become an seamless one.
This is the most common procedure for industrially made tyres. Now, what sets this apart is that the rubber (synthetic in most cases nowadays) is vulcanised several times and this makes it less supple, less flexible compared to natural rubber which was only vulcanised once.
Now I'm far from being a chemical engineer but the trick is of course to formulate a rubber compound that remains flexible enough, does not cut easily, offers good grip and so on after it has been vulcanised onto the casing.
A casing that will already contain a rubber layer for the tread to vulcanise on to.

Traditional handmade tyres* (mostly tubulars) use different procedures in that the entire casing is coated in several layers of latex (which is of course not vulcanized) upon which the tread is glued. You can't (to the best of my knowledge) vulcanise onto a latex layer directly.
Now, from the description of both procedures it becomes clear that the handmade tyre will maintain a far higher amount of flexibility since the sidewalls are merely protected by latex and the least flexible part (assuming no anti-puncture belt) is the central tread.

So, logically it will take one hell of a good compound to beat the handmade tyre. Not impossible but not very obvious to achieve.
One could easily go on for days like this but I'll stop the rant right here.

*There are several ways to go about this but nowadays the procedure is grosso modo as described above.

Hope this helps, ;)

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Posted: Tue Mar 11, 2014 9:31 pm 


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PostPosted: Tue Mar 11, 2014 10:44 pm 
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Joined: Tue Jan 22, 2013 6:23 am
Posts: 375
uraqt wrote:
@ bombertodd "The first Evo CX didn't have great grip in the wet" Compared to what?

I think Vittoria is the "cream of the crop" : )

IME The open pro has always been better than other brands matching releases. It's only limit is wear for the heavy guys. Never a side wall cut and much better in the wet than any other brand.


It didn't have great grip in the wet compared to the second and third versions. I still feel the first Evo CX was a great tire overall. Although the first version still had better grip than some other tires I've ridden such as GP4000s.

I'd agree that Vittoria is is one of, if not, the cream of the crop. I really like my Veloflex Corsa's too.


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PostPosted: Wed Mar 12, 2014 2:45 am 
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in the industry
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Joined: Sun Jul 29, 2012 2:59 pm
Posts: 634
Location: Ruidoso, NM
wassertreter wrote:
Call my a tyre nerd, but wasn't the conventional wisdom that handglued tyres were the best, and I think Jan Heine has been quoted saying the same here in this thread? Now in his blog entry about the Compass tyres, Heine says vulcanized was better, because the tread was not under tension when the tyre is inflated. I can see how a tension-free tread helps prevents (or at least limiting) cuts.


To get the tread "stress free" when inflated, wouldn't the tread need to be attached with the tire inflated? On a hand-glued tubular that is theoretically possible, but I can't imagine it happening with any clincher or vulcanized tubular.

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PostPosted: Sat Dec 20, 2014 10:55 pm 
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Joined: Sat Dec 20, 2014 9:54 pm
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Interesting topic, that I happened to land on just today. There are some comments that may benefit from further explanation. For example, the pendulum roller to measure the rolling resistance coefficient of a tire (see Youtube link in post #13 on page 1 of this topic ; as a novice I'm not allowed to post links). I didn't see the theory of the roller explained. The scientific background is in the paper of Barry J. Hill, Measurement of the Rolling Resistance using an Excentrically Weighted Oscillating Wheel, in Surface Characteristics of Roadways, ASTM STP 1031, 1990, pp 497-504 or in the paper of Wang, Macedo and Reid, A method for quantifying the rolling resistance of bicycle tires, in Engineering of Sport 5, Volume 2, 2004, p. 132 .

In my opinion, the main observable to focus on is not the time-to-standstill but the total distance that the wheels cover rolling back and forth. Measuring the amplitude or angles at several turning points and doing an reasonable regression to zero amplitude would directly yield the Crr value.
It has several advantages over a coasting-down method, such as requiring only a very short track, about half of the wheel circumference, and not requiring a long and perfectly flat surface. The vehicle is not only able to measure the Crr of tires, wide and narrow at variable pressure, but also the effect on Crr of a rough surface, like chip-sealed asphalt. However, in the end it dances on a very short track, so measuring a cobblestone surface might be problematic.


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PostPosted: Sun Dec 21, 2014 1:30 am 
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Joined: Tue Aug 12, 2014 3:50 pm
Posts: 135
Location: FIN
Bit OT, but seeing topic 1st thought was " how much it takes to see someone "defending" Continental tire (?)" .

7 posts only :mrgreen: :shock:

( if your thoughts -as mine- lead to conclusion that Shimano/Conti trendsetting is real and exist on this forum, in more non-subtle form than it should, you are naturally wrong… or not :thumbup: )

It start to be pathetic…


_______________________

Any test of rr made has certain margin of reliabilty caused mainly by procedure( lets think for a while that someone really want to make test without any influence from manufacturers/ dealers / advertisiers - hard to believe, but imagine that can happened ) . To measure REAL crr values it would take far more time & effort & will generate cost of it being comercially ( for magazine ) unjustified. And what even worse , results ( difference between models ) can be very surprising .

factors which should be considered to receive relaible results :

1. closed track with defined 3 types of tarmac : from glass-flat to harsh, surface dry + wet .
2. air temperature, tests made in 3 different ( 10-20- 30*C for example )
3. air pressure : lets say 1013HPa, 980 and 1045
4. height ( over the sea level ) : 500, 1000, 1500
5. humidity : low , mid, dry
6. load ( imaginable rider + bike weight : 70-80-90kg f.e. )
7. tire temperature ( cold and warmed up )
8. rim variability ( elasticity , profile width )
9. front/ rear wheel load ( different weight balance for tt/ tri / road )
10. Various tire pressures for all tests for certain tire with factor of butyl & latex tube
11. resistance on straight and cornering
12. same downhill & uphill ( weight load variable )
13. season ( air density ) & weather
14. what was used to pump tire : air, Co2, N … (?)
15. high and low cadence ( different load- rear tire bend on stroke )

Sounds - at least - crazy :) But let's be "precise" - to the end . with or without any sense of it .

list can be very long… no one will make it . ever. It cost money. Not even 1 manufacturer will agree to share so enormous costs of that kind of test, not knowing result :)

But seriously :
Just maybe it doesn't have any sense ? I mean in real life & on certain level of product. For magazines and manufacturers tests do have sense ;) specially these showing Conti GP4000S2 superiority :mrgreen:



I like to watch what use athletes which are good enough to use what they want instaead of what they are paid for. My observations ( and small experience ) are way different from any tests results and "common" opinions. By common I mean adverts ( payed and hidden ) , tests results & Co.

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Go to Heaven for the climate, Hell for the company.
Mark Twain


I can be wrong, and have plenty of examples for that ;)


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