From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.racing
Subject: Re: Sew-ups---old ones, gravel and aging?
Date: 26 Aug 1999 16:52:07 GMT

Carl Sundquist writes:

>> Could be.  Webster's Dictionary- Dry rot: a decay of seasoned
>> timber caused by fungi that consume cellulose of wood leaving a
>> soft skeleton which is readily reduced to powder.

> I checked, you're right about the dictionary definition. However,
> also in common usage, dry rot is frequently the description for
> cracking rubber tread or sidewalls on tires. I'll try to get someone
> from Goodyear or Michelin to support that statement, though.

The point is that you shouldn't keep a raft of tires around, aging to
uselessness.  Use new tires and be done with it.  Aged tires are only
as good as how little they age, so why age them?  As I have said, the
tire aging concept was developed by bike shops that had too much
inventory in winter and needed a way to get tires off their shelves.

>>> As for your comments about freezing the tires to preserve them,
>>> I'll trust your suggestion is an effective and correct one.
>>> However, doesn't the act of lowering the temperature below
>>> freezing also cause the rubber to become brittle, or is the
>>> temperature of the standard home freezer sufficiently warm to not
>>> cause this?

>> That depends on how cold you make it and whether you intend to ride
>> the tires in the freezer.

> You must have an awfully large freezer. Does Rocky punch sides of
> beef in there?

>> I have ridden on tubulars in weather colder than most home freezers
>> reach and they worked well.

> What temperature would you consider too cold to store tires?

You mean "too cold to ride" I suppose.  Just try it out.  Toss an old
piece of tubular in your freezer and see how flexible it is when cold.
I doubt that you'll notice any difference unless you have a cryogenic
freezer.

>>> I doubt many of us are in the position to have freezers large
>>> enough to store tubulars mounted on rims, so which way is likely
>>> to cause less damage: storage in a cool (room temperature), dry
>>> place on rims, or in the wife's freezer, folded up in a garbage
>>> bag where the kids might knock them around as they dig for
>>> popsicles and ice cream?

>> What your children do to the tires is your problem and has little
>> to do with ways of preserving relics.

> Most people do not have freezers dedicated to storing tubulars.
> Thus, any tires stored in the household freezer are likely be
> jostled around, however inadvertently.  Since the tires would have
> to be folded to fit in the freezer, I was wondering about the
> effects of a cold (from a frozen H20 standpoint) tire being unfolded
> and refolded as it is moved around or in and out of the freezer.

You make that sound like an unruly hoard.  I'd rather not get into a
discussion on how you get along with family members.

>> Why should tubulars be stored on rims?

> How about for keeping the rubber in the shape it was originally
> formed in and designed to be used in?  Have you ever had a tubular
> folded where you folded it back on itself so the tread is concave as
> opposed to convex, the way it was designed, and left it that way for
> a year or longer?  When you finally unfolded it, chances are it had
> cracks in the bend where it was folded in the opposite direction it
> was shaped.

Those are signs of aging accelerated by stress.  Stressed materials
oxidizes and out-gas more rapidly than relaxed materials.  However, at
low temperature, these effects are retarded, the colder the slower
they progress.

> Did you know that several tubular manufacturers box their highest
> quality tubulars in flat, square boxes so they will be shipped in
> the round shape in which they will be mounted on rims and used,
> rather than in a long rectangular box like they stuff the cheap
> tires into.

That seems to be symptomatic of the slow turnover these tires have.
Age cracks at the ends of a laid flat tubular was always an indication
of old stock.  Clement was one company that dated their tires so this
assessment was born out by the markings.  Stop buying those tires in
oversized pizza boxes.

> Since relatively few consumers will see the boxes the high-end tires
> come in from the manufacturer, it isn't a marketing ploy like you
> refer to with shops saying steel frames wear out, so why would the
> tire manufacturers bother with different, less space efficient boxes
> if it was OK to ship them the same way as the cheap tires?

It's either a ploy or they have inventory problems.  I've seen, used
and repaired more tubulars than most riders will ever see again.  It
isn't a new art.

>> From my experience, the difficulty of mounting an old tubular arose
>> from Continental whose tubulars had a non-biased base tape, one
>> that also shrunk with age.  I know only of a few people locally who
>> rode on these and without much success.  Just the same, we seem to
>> have inherited Continental tubulars' need to be perpetually
>> stretched.

> No more stretched than when mounted and glued on a rim, so what is
> the difference?

The difference is that you can stretch the tire when you are ready to
mount it.  You don't have to store it that way unless it has a base
tape that won't stretch and inconveniently shrinks while it ages.

>> I haven't ridden a tubular since Clement closed their Italian
>> (Milano) production, a production line that I had the pleasure of
>> visiting in the late 1950's when they made the best tubulars in the
>> world.

> What year did they close the factory?  Is that when they moved the
> factory to Thailand?

I don't know but it was years ago in the early 1970's.

> There are supposed to be some old French guys who still hand make
> tubulars at home or in their bike shops, but, if true, are probably
> very limited and tres expensive.

Cupertino Bike shop started by making tubulars in the 1950's when
supply from Europe was still poor.  The process is simple but tedious.
Imagine a cylinder about 2m long 20cm in diameter with a narrow 45
degree helical slot in it from end to end.  Take a spool of thread and
lay down a single layer of strands on this rotating drum, side by side
until the drum is covered.  Paint the outer surface with latex
solution and slit this unwoven cloth on the bias of the slot with a
razor.

You now have a 20cm wide band (a long trapezoid) of material with
cords laying diagonal at 45 degrees, held together only by the latex
coating.  This band if folded in half lengthwise so that the partially
cured latex sticks to itself to make a two ply band 10cm wide.  A
shear is used to trim both edges to the width necessary for the tire
size.  The ends of the band have an exposed single layer part that
exactly match each other when closed in a loop and, if carefully
overlayed, make a seamless two ply circular band, the tire casing.

An 8mm wide selvedge, through which the tire seam will be stitched, is
sewn along both sides of the casing into which latex tube is laid as
it is formed into a channel.  A 20mm wide band of soft cloth is sewn
inside the edges of the channel shaped casing as a stitch protector to
prevent chafing the thin latex tube.  The casing is then sewn shut,
painted with a coating of latex for a base tape and inflated on a rim
like fixture.  The tire is painted with a coating of latex to which
the tread that has also been primed with latex is applied.  The tire
is complete.

Jobst Brandt      <jbrandt@hpl.hp.com>