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PostPosted: Wed Apr 10, 2013 7:29 pm 
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fdegrove wrote:
How are these "Grand Bois" tyres made? Vulcanized or glued on?


The basic Grand Bois are vulcanized and didn't do so well in the tests. However, the newer "Extra leger" versions weren't tested. He notes these "feel" supple but testing would need to determine what actual rolling resistance is.

We can pick on details of testing, but it's enormously refreshing when a magazine grapples with real numbers rather than doing a few test rides and reports on how the tires "feel".

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PostPosted: Thu Apr 11, 2013 12:12 am 
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Hi,

Quote:
We can pick on details of testing, but it's enormously refreshing when a magazine grapples with real numbers rather than doing a few test rides and reports on how the tires "feel".


What I feel is utterly intriguing is when "feel" correlates with actual data or, even more intriguingly, when it does not.
Science often tends to ignore the human factor, tends to reduce men to machines. Tends to overcalculate.

There's something to be learned from the french culture. Just as there's something to be learned from the german culture and anything inbetween.

To get results the art is to juggle all of these factors. And that is an art, not science, as it would somehow magically combine all of the engineering contradictions and yet respect our perceptions at the same time.

There's always the same set of compromises dooming at the horizon: shall I puncture, how fast am I ?

Ciao, ;)

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PostPosted: Sun May 19, 2013 3:25 am 
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djconnel wrote:
They ride a track with a Powertap, possibly with an SRM as well (in most recent tests), at a moderate speed (150 watts, resulting speed 23-28.5 kph) then use AnalyticCycling to extract a Crr, which they temperature-adjust using results from a control tire. This isn't the most scientific method possible, as they don't say how they adjust for Crr..


Sorry I missed this discussion last month, Dan. Thanks for posting. I was thinking about buying the magazine, but figured I'd see if there was any commentary.

And... it doesn't look promising... like the coast down tests they did. We all wish testing Crr was this easy, but unless they do a lot of runs and a lot of swapping and determine that the scatter is acceptably low, then the numbers don't mean much. A Challenge Roubaix 27 (a fat smooth riding open tubular with little puncture resistance, that gets rave reviews for ride quality) nearly as bad as a Gatorskin?

Any variation in body position and wind can have a big effect. If they assume that wind drag is constant, then they must prove that this is the case. Did they attempted to prove it?

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PostPosted: Sun May 19, 2013 6:56 am 
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It always buggers the question: Why not someone do all their rolling tests on a roller coated with a tarmac surface instead? And to make for some comparison, some charts that are run on bare rims. :noidea:


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PostPosted: Sun May 19, 2013 2:45 pm 
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There is a place in Finland that has an impressive array of equipment for testing Crr and traction on a variety of surfaces. Unfortunately their findings are proprietary (they work for the tire companies).

I don't know that putting asphalt on our little rollers would work. The Crr is already greatly amplified by the roller size, so the effect of roughness would be different than it is on the road. We'd need a large roller, a precise load, and precise measuring equipment.

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PostPosted: Sun May 19, 2013 4:20 pm 
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Even if asphate would work I'd worry about the thin strip getting worn and changing over time. But more imporatantly my last ride I had everything from very rough roads (dirt that they just poured asphalt over), to freshly laid and rolled tarmac.

As long as the roller test don't re order then I'm good with them.


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PostPosted: Mon May 20, 2013 4:14 pm 
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BQs tests indicate a lot of re-ordering... that's the issue.

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PostPosted: Mon May 20, 2013 11:02 pm 
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Hi,

maxxevv wrote:
It always buggers the question: Why not someone do all their rolling tests on a roller coated with a tarmac surface instead? And to make for some comparison, some charts that are run on bare rims. :noidea:


Because if you want to test rolling resistance and nothing else any surface will do.
How a tyre performs on a road surface in the real world depends on a lot more parameters than just mere rolling resistance.

Ciao, ;)

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PostPosted: Tue Aug 13, 2013 3:26 am 
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Has anyone noticed a correlation with Crr and how high these tyres bounce?

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PostPosted: Tue Aug 13, 2013 4:13 am 
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I haven't heard of that but it makes sense that there would be a correlation. Good tires would bounce better.

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PostPosted: Tue Mar 11, 2014 3:20 pm 
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Getting this old thread back to the front.
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.

What do the experts here say?

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PostPosted: Tue Mar 11, 2014 4:09 pm 
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The first Evo CX didn't have great grip in the wet. But the Evo CX II and CX III have great grip since they added ISOgrip to the tires.


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PostPosted: Tue Mar 11, 2014 5:18 pm 
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Hi,

Quote:
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.


That's a lot of assumptions.

If hand glued tyres are indeed superior I don't think that has much to do with the fact that these are hand glued but rather the use of superior material (natural rubber, higher TPI cotton casing, etc.).
Secondly inflate any tyre, regardless of how it is constructed and the tread will be tensioned.

I'm probably as much a tyre nerd as you are but if you want to make a better tyre than what's commercially available then ask a company such as FMB. They can do it albeit at a premium.

Ciao, ;)

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PostPosted: Tue Mar 11, 2014 8:32 pm 
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bombertodd wrote:
The first Evo CX didn't have great grip in the wet. But the Evo CX II and CX III have great grip since they added ISOgrip to the tires.

Really? I was under the impression that only the III would have it. Currently pondering to get some on-sale ones, as detailed in this thread viewtopic.php?f=113&t=123799 . Thanks for any insight.

fdegrove wrote:
I'm probably as much a tyre nerd as you are but if you want to make a better tyre than what's commercially available then ask a company such as FMB.

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.

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Posted: Tue Mar 11, 2014 8:32 pm 


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PostPosted: Tue Mar 11, 2014 8:45 pm 
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@ 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.


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