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:

http://home.comcast.net/~carlfogel/download/Goathead.jpg

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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