Puncture proofing

On Wed, 05 May 2004 09:34:14 +0200, Dieter Britz <[email hidden]>

Quoted message said:

I note that I can buy a couple of kinds of plastic strip to
put in under the tyres, guaranteed to prevent punctures.
One type is called "Slime" (it's sort of greenish), the
other "Nix Panne" (meaning no punctures). They look like
plastic, but I wonder what (supposedly) makes them so
strong. Anyone know what material they are made of? Where I
live, there is a fair amount of flint chips on the road,
and these needle shaped bits even get through Kevlar, so
how come... ?

Dear Dieter,

Whatever specific tough plastic is used in pliable tire
liners, they work in two ways.

First, the solid liners often stop broader sharp-edged
debris from cutting through--the tire is gashed, but the
plastic liner protects the inner tube. The liner edges
typically feather out, so there's less protection at the
edges, but the centers of some brands of liners are tough
enough to stop sharp-edged fragments of rock, glass, and
metal. They're even tough enough to stop some modest thorns.

Second, the liners work just like integrated kevlar belts
by making the tire thicker. Yes, thorns can go through
kevlar threads like needles through steel wool. And yes,
hard thorns can sometimes drive through plastic liners
(solid material, not threads). But the extra thickness may
still stop the thorns short of puncturing the inner tube--
many thorns just aren't long enough to reach through alll
that material.

Such liners are quite popular in hot, dry areas of the U.S.,
where the goathead thorn is widespread. Here's a picture of
a goathead on a 13mm wide dime that shows how short its
wicked thorn tips are:

home.comcast.netGoathead.jpgOpen ↗

They're long enough to lance through a tire and inner tube,
but the extra layer of a plastic liner can stop the thorn,
deflect it, or simply prove too thick.

Unfortunately, the tire liners add weight, increase rolling
resistance, and complicate mounting tires.

Carl Fogel

Dieter Britz <[email hidden]> wrote: [Tyre liners]

Quoted message said:

Where I live, there is a fair amount of flint chips on the
road, and these needle shaped bits even get through Kevlar,
so how come... ?

Kevlar is a woven fabric, and so is easily penetrated by
long thin objects. A tyre liner is solid. However, I suspect
much of their effectiveness simply comes from increased
thickness; an object that isn't long enough to be driven all
through the tyre and liner will stay stuck in the tyre, but
not reach the tube...
--
David Damerell <[email hidden]>
Distortion Field!

David Damerell <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Dieter Britz <[email hidden]> wrote: [Tyre liners]

Quoted message said:

Where I live, there is a fair amount of flint chips on
the road, and these needle shaped bits even get through
Kevlar, so how come... ?

Kevlar is a woven fabric, and so is easily penetrated by
long thin objects. A tyre liner is solid. However, I
suspect much of their effectiveness simply comes from
increased thickness; an object that isn't long enough to
be driven all through the tyre and liner will stay stuck
in the tyre, but not reach the tube...

While touring across Nevada, I had a small spine go
right through a
mr. toughy. I don't use them anymore. I just accept my flats
and fix them. They probably do help for some situations.
But they are heavy and increase rolling resistance. I
didn't care about the weight when touring, but I was
never clear on if the higher rolling resistance was
"worth it."

gwhite said:

David Damerell said:

Kevlar is a woven fabric, and so is easily penetrated by
long thin objects. A tyre liner is solid. However, I
suspect much of their effectiveness simply comes from
increased thickness;

While touring across Nevada, I had a small spine go right
through a
mr. toughy. I don't use them anymore.

I never have used them. These days I flat about once every
1,000 miles, which I ride at an average of about 15mph (most
of my riding is my commute, which I do quickly because that
means more time in bed in the morning...); so I spend 67
hours riding between each flat. Fixing a flat takes me 15
minutes for a rear wheel with an elusive penetrator (I don't
count the tube-fixing time because I can do that at home
while watching TV or something), but sometimes I miss a half-
hourly train or something, so the actual loss in time is
probably more like 20 minutes. Hence if a puncture-proofing
system was 100% effective (which they're not) I would still
lose time if it slowed me down by 0.5%.
--
David Damerell <[email hidden]> flcl?

On Wed, 05 May 2004 09:34:14 +0200, Dieter Britz <[email hidden]>

may have said:

I note that I can buy a couple of kinds of plastic strip to
put in under the tyres, guaranteed to prevent punctures.
One type is called "Slime" (it's sort of greenish), the
other "Nix Panne" (meaning no punctures). They look like
plastic, but I wonder what (supposedly) makes them so
strong. Anyone know what material they are made of? Where I
live, there is a fair amount of flint chips on the road,
and these needle shaped bits even get through Kevlar, so
how come... ?

As others have said, one of their ways of reducing punctures
is by simply putting more material in the path of the
object, so that more damage must be done before the tube is
actually reached. Some of the liners I've seen are made from
a plastic that's both stretchy and clingy; it seems to
engulf and grab the puncturing object rather than allowing
itself to be cut; sort of a variaion on the Zen "bend with
the wind" theory. All liners add weight and increase the
complexity of tire installation. I've used just one pair,
and I can't really say that they did much, as I don't get a
lot of flats in any event. An acquaintance used to swear by
them until he took a trip to California and encountered the
infamous goathead weeds. He quickly concluded that the best
defense in that case was avoidance coupled with a setup that
permitted the speediest possible patch-and-pump process,
which made the liners somewhat less productive. He also
learned that in goathead country, one needs shoes with
thick, wide, hard-to-puncture soles; while patching a tube,
two goatheads speared his foot right through the shoe next
to the edge of the sole.

--
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