Filling a tube with water

Joe Riel wrote:
I resorted to
filling the tube with water, using my frame pump (remove plunger, fill
with water, pump into tube). I learned of this technique on this
newsgroup, probably from Jobst Brandt; this was the first time I had
to put it practice. It worked very well, the tire stayed hard and
showed no signs of leaking.

I never would have guessed this but the more I think about it, the
more it makes sense. I expect it probably was leaking while you
were riding but only very slowly; which was apparently good enough.
I suppose it would have something to do with how big the hole is.
A pin prick hole is not going to let water out quickly. A bigger
hole might be more of a problem.

Good to know.

"Larry Schuldt" wrote: (clip) Water isn't under pressure; the tire is hard
because water simply doesn't compress.
^^^^^^^^^^^^^^^
Then again, maybe it is under pressure when the tire is under load. The
pressure on the contact patch, between the tire and the road x the area of
the contact patch has to equal the load on the tire, whether it is full of
air or water. Since the tire walls have nearly zero stiffness, the pressure
inside the tire must equal the pressure on the outside bottom.

My guess is, however, that the tire is not as full and distended when it is
"filled" with water, so the contact patch is probably larger, and the
pressure is lower. Wat you tink, Jobst?

On Fri, 20 Aug 2004 00:57:44 GMT, "Leo Lichtman"
wrote:


"Larry Schuldt" wrote: (clip) Water isn't under pressure; the tire is hard
because water simply doesn't compress.
^^^^^^^^^^^^^^^
Then again, maybe it is under pressure when the tire is under load. The
pressure on the contact patch, between the tire and the road x the area of
the contact patch has to equal the load on the tire, whether it is full of
air or water. Since the tire walls have nearly zero stiffness, the pressure
inside the tire must equal the pressure on the outside bottom.

My guess is, however, that the tire is not as full and distended when it is
"filled" with water, so the contact patch is probably larger, and the
pressure is lower. Wat you tink, Jobst?


Dear Leo.

I propose freezing the water-filled tire.

The slight expansion should improve the pressure, and ice
won't leak out a pinhole.

Some might complain about the harshness of the ride, but
progress has its price.

I'm curious about how a water-filled tire like this behaves
when it hits a nasty bump.

Carl Fogel

wrote: (clip) I'm curious about how a water-filled
tire like this behaves when it hits a nasty bump.
^^^^^^^^^^^^^^^
Better than and ice-filled tire, I'll wager.

Leo Lichtman writes:

Water isn't under pressure; the tire is hard because water simply
doesn't compress.
^^^^^^^^^^^^^^^^

Then again, maybe it is under pressure when the tire is under load.
The pressure on the contact patch, between the tire and the road x
the area of the contact patch has to equal the load on the tire,
whether it is full of air or water. Since the tire walls have
nearly zero stiffness, the pressure inside the tire must equal the
pressure on the outside bottom.

I agree. The incompressibility of water in comparison to air means
that tire deformation, that causes minimal volume change with respect
to air inflation, is enough to pressurize water.

My guess is, however, that the tire is not as full and distended
when it is "filled" with water, so the contact patch is probably
larger, and the pressure is lower. Wat you tink, Jobst?

In both instances in which I filled a tire with water, I made a good
effort to make sure there was no air and that the pump would add no
more water before I screwed the valve shut. As I said, I did not make
a print of the contact patch but from the riding position, I could see
not difference in the (front) tire. My nephews water filled rear
tubular tire, likewise, looked no different and he rode it for a week.

Jobst Brandt

Carl Fogel writes:

I'm curious about how a water-filled tire like this behaves
when it hits a nasty bump.

I think we need an experimenter. I never gave that a thought because
from my first attempt, we rode on rough roads and plenty of miles with
fast descents. When I did the shimmy test with the water filled front
wheel, I didn't notice any change in performance and didn't do any
particular tests. Afterwards, I let out the water in stages by
draining and inflating with air until no water came out (with the
valve at the bottom and the tire flat on the floor).

If that tire hasn't had a flat since, then there is probably a wet
tube in it.

Jobst Brandt

wrote in message
...
Carl Fogel writes:

I'm curious about how a water-filled tire like this behaves
when it hits a nasty bump.

I think we need an experimenter. I never gave that a thought because
from my first attempt, we rode on rough roads and plenty of miles with
fast descents. When I did the shimmy test with the water filled front
wheel, I didn't notice any change in performance and didn't do any
particular tests. Afterwards, I let out the water in stages by
draining and inflating with air until no water came out (with the
valve at the bottom and the tire flat on the floor).

If that tire hasn't had a flat since, then there is probably a wet
tube in it.

Jobst Brandt


I would have imagined that a tube filled with water from a pump (i.e. to
50psi) would behave much like a solid rubber tyre (as in children's
bicycles/some industrial bikes. As my experience with such tyres has been a
horrible ride, why does a water filled tyre behave differently - unless the
tyre casing has a considerable amount of stretch - but perhaps it does?

Hugh Fenton

Hugh Fenton wrote:

I would have imagined that a tube filled with water from a pump (i.e. to
50psi) would behave much like a solid rubber tyre (as in children's
bicycles/some industrial bikes. As my experience with such tyres has been a
horrible ride, why does a water filled tyre behave differently - unless the
tyre casing has a considerable amount of stretch - but perhaps it does?

Rubber is viscoelastic and consumes energy as it flexes. Water is
not viscoelastic and thus consumes almost no energy as the tire
flexes.
--
terry morse Palo Alto, CA http://bike.terrymorse.com/

On Fri, 20 Aug 2004 08:26:53 -0700, Terry Morse
wrote:

Hugh Fenton wrote:

I would have imagined that a tube filled with water from a pump (i.e. to
50psi) would behave much like a solid rubber tyre (as in children's
bicycles/some industrial bikes. As my experience with such tyres has been a
horrible ride, why does a water filled tyre behave differently - unless the
tyre casing has a considerable amount of stretch - but perhaps it does?

Rubber is viscoelastic and consumes energy as it flexes. Water is
not viscoelastic and thus consumes almost no energy as the tire
flexes.

It is also possible that despite best efforts to squeeze out all the
air a pocket of air remained. As the water was pressurized bt hitting
bumps, this pocket of air could compress like a shock absorber. Just a
theory.

Hugh Fenton writes:

I'm curious about how a water-filled tire like this behaves
when it hits a nasty bump.

I think we need an experimenter. I never gave that a thought
because from my first attempt, we rode on rough roads and plenty of
miles with fast descents. When I did the shimmy test with the
water filled front wheel, I didn't notice any change in performance
and didn't do any particular tests. Afterwards, I let out the
water in stages by draining and inflating with air until no water
came out (with the valve at the bottom and the tire flat on the
floor).

If that tire hasn't had a flat since, then there is probably a wet
tube in it.

I would have imagined that a tube filled with water from a pump
(i.e. to 50psi) would behave much like a solid rubber tyre (as in
children's bicycles/some industrial bikes. As my experience with
such tyres has been a horrible ride, why does a water filled tyre
behave differently - unless the tyre casing has a considerable
amount of stretch - but perhaps it does?

When the tire is full the last stroke stops hard and even if there were
pressure in it, the slow leak it was hiding would let that pressure
out. Even if there were a bit of residual air in the tube, it was
mighty small and therefore a spring with little pressure to offer.

Jobst Brandt