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PostPosted: Thu Feb 27, 2014 9:27 pm 
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Location: Austin, TX
WMW wrote:
rmerka wrote:
The one issue I've had with latex tubes in clinchers was a sudden blowout when I found myself on an extremely bumpy, and I mean extremely bumpy, road that was also super steep 20% + downhill and I laid on the brakes too hard. Pow lost the front tire and barely managed to stay upright. Found a burn mark and hole where the latex popped.


Latex tubes are unforgiving of poor installation. They are so tough that they will survive if you pinch them under the bead... then fail when you have high temperatures or forces.

When properly installed there is very little force on the tube... it just sits there creating an air barrier. You won't get a "pow!" unless the container fails... and that won't be the tube's fault.


The tube didn't make a sound when it went flat and it wasn't pinched in the bead. It just melted the tube from me braking too hard for too long. Latex melts at about half the temp that butyl does. With respect to temperature latex is most certainly more fragile.

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PostPosted: Thu Feb 27, 2014 11:01 pm 
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wassertreter wrote:
WMW: if you could share how you come to that conclusion (edit: re Heine's testing), that would be great. It seems people are either strongly following, or rejecting Jan Heine's work, but I've never seen the critique being substantiated beyond "one doesn't test like that". I'm an engineer myself, but not in a mechanical field, and interested to understand the issues at hand better.


Jan did coast down tests on a full bicycle... on different days. Anyone who has looked at the physics knows that aero drag dominates the test he did, and slight changes in wind or position will swamp the small differences between tubes... or tires for that matter.

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PostPosted: Thu Feb 27, 2014 11:05 pm 
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rmerka wrote:
The tube didn't make a sound when it went flat and it wasn't pinched in the bead.


Then what was that "pow" you mentioned and why did the tire come off?

Like I said, a properly installed tube has very little stress. Zipp tested latex tubes and found that the rim strip would melt and fail before the tube had an issue from heat.

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PostPosted: Fri Feb 28, 2014 12:14 am 
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Tire didn't come off, poor choice of words in the first post. Also the rim is 202 carbon clincher and the rim strip didn't melt. I think I still have the tube. I'll post a pic of the burn if I can find it.

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PostPosted: Fri Feb 28, 2014 3:27 am 
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WMW wrote:
wassertreter wrote:
Jan did coast down tests on a full bicycle... on different days. Anyone who has looked at the physics knows that aero drag dominates the test he did, and slight changes in wind or position will swamp the small differences between tubes... or tires for that matter.


You can read about the test at the link below. He claims they only did this on mornings with perfectly calm winds and that they (later in a wind tunnel) confirmed the rider was able to hold a very consistent position. We're talking about an 800ft/245m rolldown test on a fairly modest grade hill so I doubt aerodynamic drag is all that significant.The test seems at least as relevant (if not more so) as the steel drum Crr tests which only tell you how a tire behaves on perfectly smooth surfaces.

Image

http://janheine.wordpress.com/2012/06/1 ... -of-tires/


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PostPosted: Fri Feb 28, 2014 6:44 am 
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Butyl condoms and Latex tubes, oh shit, or is it latex condoms and butyl tubes, oh man I can never remember!


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PostPosted: Fri Feb 28, 2014 9:15 am 
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dunbar42: my gut feeling would be along those lines too, but again, I'm not an expert. Having only read the online material, not print, I think they have been making an effort in working out which of their results carry statistic significance.

On a steel drum, a steel wheel will have the lowest rolling resistance, resembling a railroad setup. But on the road or rougher surface, a steel wheel will not roll the best (apart from traction issues). Dunlop figured this out for us.

But anyway, I'm looking forward to try bigger tubulars with latex tubes this spring.

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PostPosted: Fri Feb 28, 2014 10:45 am 
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I'm getting the feeling that a little bit of damping (i.e. hysteresis) in the tire might actually be a good thing in the real world (as opposed to lab tests on smooth surfaces without a rider) since it will reduce the transfer of vibrations to the rider by reducing the spring-back of the tire and thus transferring less energy to the rider's mass.

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PostPosted: Fri Feb 28, 2014 11:05 am 
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The failure could have been a defective tube and if it happened to a second one it could have been a defective batch. It happens in pretty much so anything that is manufactured. I've only used Michelin latex tubes and my experience goes over many years and have much greater confidence in latex over ultra thin butyl tubes or even semi light butyl. Your competition will be using latex to get an edge over you. :shock:

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PostPosted: Fri Feb 28, 2014 4:16 pm 
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I read this interview the other day with Josh Poertner, former Zipp employee. He seems to believe in latex tubes. Good enough for me.

http://nyvelocity.com/content/interview ... h-poertner


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PostPosted: Sat Mar 01, 2014 10:40 pm 
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WMW wrote:
Jan did coast down tests on a full bicycle... on different days. Anyone who has looked at the physics knows that aero drag dominates the test he did, and slight changes in wind or position will swamp the small differences between tubes... or tires for that matter.

The thing is, this sort of random variance can be handled quite well using statistical methods. If they are doing due diligence -- which they claim -- then the findings can still be relevant.

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PostPosted: Sun Mar 02, 2014 3:18 pm 
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I'm trying to find some decent light tubes to buy as a batch (for the kids's clincher wheels, and spare tubes).

But unfortunately, I only had bad luck with ultra light butyl tubes.
Mostly Vittoria and Michelin.
They seem to be even more prone to flats than latex.

Any recommendation for an ultralight butyl tube that served you well ?


Louis :)


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PostPosted: Sun Mar 02, 2014 4:10 pm 
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There is an obvious quality difference between latex as well. I used to ride Vittoria Corsa Evo CX 23c tubulars. By the next morning, nearly flat after a ride.

Became really disenchanted and disappointed in Vittoria.. The quality, finish, valve area, real garbage lately. Once I got a hold of some Veloflex Carbon tubulars...yes, a step above IMO.

Those will hold air for days, never really go flat at all between rides. So there is something different going on with those compared to the Vittoria latex tubes. Valve holes were all sealed/plumber tape real well, so it wasn't leaking from there at all.

Currently riding a Conti Force rear tubular, 24mm butyl, Veloflex Carbon 23c front/latex. The ride is pretty much the same until you drop the pressure to 90psi. 95-100psi+, the ride is very similar between the two. They are mounted to 56mm wide/tubular carbon rims strung up tight.

Hope I get an extra 5watts out of the Veloflex though, I need it during a race.


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PostPosted: Sun Mar 02, 2014 8:19 pm 
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Location: Belgium
Hi,

Quote:
They seem to be even more prone to flats than latex.


That's perfectly logical as butyl does not have (by nature) the extremely high stretch factor of latex (especially natural, unpigmented latex) so it can not conform around an object the way latex can. Hence the add anti-puncture advantage of latex over butyl.

Just as WMV, I too am rather sceptical of the ability of thin butyl tubes to have lower RR than latex. Seems highly unlikely given the above.

I've never seen latex burn. Seen stretch marks and signs of overheating. If you do spot this then replace the tube immediately.
Latex is impossible to manufacture uniformly so don't pump it up (over half a bar say) outside its envelope as you'll likely damage it.

Correct me if I'm wrong but isn't latex about 90 times more flexible than butyl?

Ciao, ;)

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PostPosted: Mon Mar 03, 2014 3:54 am 
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dunbar42 wrote:
He claims they only did this on mornings with perfectly calm winds and that they (later in a wind tunnel) confirmed the rider was able to hold a very consistent position. We're talking about an 800ft/245m rolldown test on a fairly modest grade hill so I doubt aerodynamic drag is all that significant.The test seems at least as relevant (if not more so) as the steel drum Crr tests which only tell you how a tire behaves on perfectly smooth surfaces.


Sure... no wind (0.0 mph... really?) and a perfectly consistent position... right. If you are able to compute the effect of these variables, please do so and get back to us. I did... and I don't believe any of the results.

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