[email protected] wrote in message news:<
[email protected]>...
> JP writes anonymously:
>
> >>> I think that as latex tubulars get older they leak more. I read somewhere that you should let
> >>> the air out of them after your ride because leaving them at pressure makes them more porous.
>
> >> "I read somewhere" is a seemingly safe way to to pass on myth and lore, which this is. What
> >> happens is that latex tubes lose their elasticity with exposure to oxygen and especially ozone.
> >> They pinch flat more easily in that state but do not leak faster. They also tear easily when
> >> trying to patch them.
>
> > Myth or not, I have definitely observed with my own tubular tires that their ability to hold air
> > decreases with age. I had a pair of Clement Criterium Setas that lasted a long time but
> > eventually just would not hold air long enough for more than a short ride. They may have had
> > slow leaks but the development over the course of months if not years would seem to indicate
> > that a microscopic puncture does not fully explain the effect.
>
> I suspect you had a fine puncture.
Maybe, but then you have to ignore what I said: it was a pair and they progressively lost their
ability to hold air.
> What did you find when you opened the tire. How did the tube look?
I don't remember. I think I tried to find a leak, couldn't, and threw them away.
> Do you patch tubulars and how?
Using a Velox kit, for almost 30 years now. However, I read something recently about patching
latex tubes with liquid latex. I don't know about that, but at a time and place where no one used
butyl tube sewups (not sure they existed in the mid-70s- I never saw one then), the Velox kit was
the way to do it.
> I have latex tubes from Italian Clement tubulars from the 1970's that are still like new, elastic
> and airtight as ever. They have been in an unsealed plastic bag all these years waiting for
> someone who needed to re-tube a tire as was often done in the days when there were no high
> performance clinchers.
Ah ha! You just presented evidence that there is something about using latex tubes that causes them
to deteriorate. Do repeated pressurization cycles cause them to loose their elasticity? Does
inflation cause microscopic tears that are exacerbated by loss of elasticity? Do I know? NO. Do you
know? Probably not, either.
> > I am not sure what evidence you have to support your claim beyond the FAQ you reference (which
> > does not address *at all* latex tubes or whether their porosity increases with age), but it does
> > seem to me that given that latex tubes are porous when new (a known fact) and that they get
> > brittle with age (according to you), that the combination of brittleness and inherent porosity
> > would tend to make them leak faster as they age.
>
> Butyl tubes are also "porous", although to a lesser degree than latex.
Well, of course they are.
> This does not mean they disintegrate with age or get leakier. That latex is damaged by oxygen and
> ozone is known but that this degrades air retention has not been shown,
One way or the other.
> only that the rubber tears easily and that this is the mode of failure.
From this it is reasonable to hypothesize microscopic tearing as a result of age and inflation, or
even from inflation alone. It is more of a "stretch" to hypothesize that deflating the tire when not
used would slow this effect. It might even make it worse.
> > As to whether deflating them helps or not, I only know what I read which was probably Bicycling
> > magazine at least two decades ago, but since I never bothered, I am relieved to know that it was
> > not the cause of the ultimate demise of my Clements, which were pretty special tires.
>
> Well how about th8inking for yourself on that issue. What do you believe deflating tubulars does?
See above. I have not been talking about deflating tubulars, although you have. I have been talking
about deflating latex tubes. What I think is that neither you nor I *knows* whether deflating latex
tubes helps them hold air better over the long run. In the absence of any knowledge it is reasonable
to defer to a generally accepted source of expertise; however, I did not bother, most likely because
tubulars don't generally last me long enough to worry about them eventually no longer holding air.
Interesting, though, I am now riding a 15 year old Clement Criterium that was first used 15 years
ago which I expected to blow up the first time I rode it. It has lasted a few thousand miles with no
flats while I have had about half a dozen flats on my other wheel. It still holds air quite well-
certainly no noticeable loss over a 2.5 hour ride. So, even mounted on a wheel, but not subject to
pressurization cycles or extended periods of inflation the tire seems to me to be in pretty good
shape. My conclusion based on my personal experience is that mere use of latex tubed tubular tires
seems to contribute to their degradation, irrespective of punctures, but I also am willing to accept
evidence to the contrary. Do you have any?
> On the one hand you are certain of what you read while deferring to unnamed authority for its
> validity.
On the contrary, I am certain only of my own experience. I don't know whether deflation really helps
preserve the integrity of latex tubulars, and neither do you.
JP
