Re: Run Flat tires

"Erik Freitag" wrote: (clip) how do the automotive run-flats work?
^^^^^^^^^^^^^^
I believe they rely on sidewalls that are stiff enough to hold the weight of
the car without collapsing completely. This idea, applied here, would
result in a pretty heavy tire.

Years ago I recall a tire that had a double wall, with a vent between the
inner and outer chambers. If the tire started to deflate, this vent was
supposed to close, allowing the tire to hold air in the inner chamber. The
design did not survive the test of time.

Erik Freitag said:

Lee Lindquist said:

Is there such a thing as run flat tires for bicycles?

Possibly separate topic - how do the automotive run-flats work?

There are two types that I can recall. One uses an ultra-low-profile
tire and wheel assembly with a high-rigidity sidewall which will
permit the tire to continue to function when deflated. The other
relies on an inner structure to support the tread at an intermediate
point of pseudo-inflation. Both have speed restrictions, IIRC.

http://www.tirerack.com/tires/tiretech/runflat/runflat.jsp

Neither tech holds much promise for bike tires in applications where
weight and ride quality are important factors.
--
Typoes are a feature, not a bug.
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Werehatrack said:

Erik Freitag said:

Lee Lindquist said:

Is there such a thing as run flat tires for bicycles?

Possibly separate topic - how do the automotive run-flats work?

There are two types that I can recall. One uses an ultra-low-profile
tire and wheel assembly with a high-rigidity sidewall which will
permit the tire to continue to function when deflated. The other
relies on an inner structure to support the tread at an intermediate
point of pseudo-inflation. Both have speed restrictions, IIRC.

http://www.tirerack.com/tires/tiretech/runflat/runflat.jsp

Neither tech holds much promise for bike tires in applications where
weight and ride quality are important factors.

I'd think the second approach would have some potential for
commuter bikes. I've ridden for up to 6 miles on a totally
flat bike tire and it didn't result in any damage to either
the tire or the rim (even the tube was patchable), but the
ride felt very unstable at any speed over about 12 mph.
Shouldn't take much of an inner hard foam support to improve
the stability enough to make for a reasonable ride at slightly
reduced speed. The main technical issue I see is to allow
for easy mounting and demounting of the tire.

I don't see there being a sufficient demand for such a design
in the US, but possibly for the European and Asian markets.

Try
http://www.greentyre.com/eng/index2.php
Alan Acock

On Mon, 13 Dec 2004 16:37:52 -0800, Peter <[email hidden]>

Quoted message said:

Werehatrack said:

http://www.tirerack.com/tires/tiretech/runflat/runflat.jsp

Neither tech holds much promise for bike tires in applications where
weight and ride quality are important factors.

I'd think the second approach would have some potential for
commuter bikes. I've ridden for up to 6 miles on a totally
flat bike tire and it didn't result in any damage to either
the tire or the rim (even the tube was patchable), but the
ride felt very unstable at any speed over about 12 mph.
Shouldn't take much of an inner hard foam support to improve
the stability enough to make for a reasonable ride at slightly
reduced speed. The main technical issue I see is to allow
for easy mounting and demounting of the tire.

There's a bigger one; the support structure must be firmly attached to
the rim or it will tend to creep around it when running deflated; if
it's internal to the tube, this will shear the valve stem off in short
order. Mark the tire's position on a rim sometime, ride it for a
block or so with it deflated, and then look at the tire's new
position. Now consider what would happen to the tube if it wasn't
free to flop around in there as the tire is squirming.

The solid tires used on cheap hand trucks exhibit the same failing;
they squirm around the rim while rotating. In some cases, the inner
surface wears out before the outer.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
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Alan C. Acock said:

Try
http://www.greentyre.com/eng/index2.php
Alan Acock

That does, indeed, look like the kind that was on the Trek that I got
to ride once. Once was enough. No, thank you, I'll stay with what I
have.

I note that in their FAQ, they state that the tires are made of
microcellular polyurethane; to me, that's one more fatal flaw, as
there is a fungus that is becoming increasingly common which eats
polyurethane. I've had a number of dead-blow hammers, squeegee blades
and urethane screwdriver grips fall to bits after being attacked by
that organism, some as early as 18 months after purchase.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Werehatrack said:

On Mon, 13 Dec 2004 16:37:52 -0800, Peter <[email hidden]>

Quoted message said:

Werehatrack said:

http://www.tirerack.com/tires/tiretech/runflat/runflat.jsp

Neither tech holds much promise for bike tires in applications where
weight and ride quality are important factors.

I'd think the second approach would have some potential for
commuter bikes. I've ridden for up to 6 miles on a totally
flat bike tire and it didn't result in any damage to either
the tire or the rim (even the tube was patchable), but the
ride felt very unstable at any speed over about 12 mph.
Shouldn't take much of an inner hard foam support to improve
the stability enough to make for a reasonable ride at slightly
reduced speed. The main technical issue I see is to allow
for easy mounting and demounting of the tire.

There's a bigger one; the support structure must be firmly attached to
the rim or it will tend to creep around it when running deflated

Sure, but that was already part of the design in the automotive
system you cited earlier: "when the tire loses pressure, it rests on a
support ring *attached* to the wheel."
The difference with a bicycle wheel is that I'd require the tire
to be easily replaceable with hand tire levers rather than
needing power tools and it would be nice if the modified rim
and support structure would work with conventional tires.