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From: (Jobst Brandt)
Subject: Re: Sew-ups---old ones, gravel and aging?
Date: 24 Aug 1999 01:08:34 GMT

Carl Sundquist writes:

> Will that prevent dry rot? I never gotten a conclusive answer on the
> prevention of dry rot.

I don't know what you understand under the term "dry rot" because
wooden structures that suffer from this are not rotting when dry.  The
pulpy rotten wood is found in the summer after the water is gone.  The
rot is water related.  I don't see how this relates to tires so I don't
foresee and answer.  However, if you means drying out, and they do that
becoming brittle and hard, you had best store these tires in a sealed
plastic bag in a freezer.  Nothing like low temperature to slow down
processes.  Bicycle tires are full of volatile solvents that make them
pliable and resilient. especially tubulars.

>> if you really want to store your sew-ups properly, coat them
>> thoroughly with talcum powder, drop them in a plastic garbage bag,
>> and use a twister to close the bag. They'll stay like new forever.

Don't you believe it.  It takes more than that to preserve them, but
why?  I suspect you are planning to buy new ones and that this is not
an exercise in preserving beautiful racing silks from the 1960's.
Tires do not get better with time so there is no benefit in "aging"
them.  That was a ploy of bike shops to get racers to buy tires in
the winter when sales were dead.  Similarly, they started the fable of
steel frames getting soft in order to sell new bicycles to people who
didn't need them.

Jobst Brandt      <>

From: (Jobst Brandt)
Subject: Re: Storing wirebead tires folded
Date: 30 Nov 1999 21:55:29 GMT

Ron Harriman writes:

> Was over in a friend's garage last weekend when he took down his
> big-bin-o-bike-parts to get some chain lube. I noticed he had a
> spare wire-bead tire folded and doubled into a figure 8 shape to fit
> the bin. (He also has a rolled Kevlar bead tire but that doesn't
> strike me as alarming.)

The reason you should not do this is not because the tire will take a
set but rather that it will deteriorate at any high stress point.
This goes for any rubber or elastomeric component.  Rubber oxidizes
and hardens, forming cracks more quickly when stressed.  You can
experiment with this by storing several rubber bands, some stretched
to twice their original length and others neutral.  The stretched ones
(the bends in a tire) will crack sooner than the others.

Jobst Brandt      <>

From: (Jobst Brandt)
Subject: Re: Will My Bikes Melt?!
Date: 1 Jun 2000 20:33:19 GMT

Terry Morse writes:

>> If you leave them in the sun, hell yeah they'll crack. But I keep
>> my rides in the house, garage, and tool shed and I haven't seen
>> them crack as you've mentioned.

> As long as you ride each set of tires often, you shouldn't see a
> cracking problem.  The act of riding flexes a tire, allowing the
> protective rubber additives to come to the surface.

Tire rubber is not a sponge and there is no migration of "additives"
in them, regardless of whether ridden or not.  What riding does, is to
wear off the oxidized rubber that is easily removed by road contact
and keeps cracks from developing.

> If you store a tire for a long time without using it, the additives
> dry out at the surface and promote cracking (even out of the sun).

Obviously tire rubber contains volatile components but what you are
seeing is oxidation and this process gives off the "smell of rubber".
If this were escaping fluids, you could toss a tire in a vacuum
chamber and age it in a big hurry.  However, that does not happen.
Aircraft that spend many hours in low pressure also have not rapid
deterioration of their tires in flight.

> I keep a van in Salt Lake City for ski trips. Most of the year it
> just sits at the airport. After two years, the tire sidewalls were
> so badly cracked that all 4 tires needed replacement.

That may be true, but I don't believe you have any link of your
proposed cause and effect.  It is much like the assumption that after
riding with higher tire pressure, no glass cuts were encountered in
the following week or so.  We have seen such claims of cause and
effect equally strongly presented here.

Jobst Brandt      <>

From: (Jobst Brandt)
Subject: Re: Dikes! Mavic T217 eats presta valve stems!
Date: 1 Jun 2000 15:55:13 GMT

Bob Mitke writes:

> Something doesn't seem right with your analysis.  You say you can't
> abrade a tube at the spoke hole, yet, I have a sample of just such
> a failure mode.  I don't understand...

I think your analysis is incorrect.  A tube stretched close to the
puncture stress over a protruding spoke, will oxidize and fail soon at
that place leaving a rough and cracked surface.  This is not abrasion.
You can test this with a slice of tube (rubber band style) and stretch
it about as far as it will go around a square object.  You'll see the
same type of failure in a week or so, especially at the corners.  You
may have noticed this anyway, somewhere else in life.  Rubber under
stress cracks and loses its elasticity.

> What is your address?  I have a section of a spoke-hole-abraded-to-
> failure inner-tube I would like to send you (only if you promise to
> send it back - I will pay for the return postage).

> Maybe you could explain how it happened...

You must think I was born yesterday.  I have had the opportunity to
see lots of these over many years.

Jobst Brandt      <>

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