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Old August 22nd 11, 09:28 PM posted to rec.bicycles.tech
thirty-six
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Posts: 10,049
Default Tire-making: bead stress, tire width, math, woe........

On Aug 22, 9:20*pm, DougC wrote:
On 8/22/2011 1:30 PM, DirtRoadie wrote:



Just for clarification, when you say "bead strength" or "stress on the
bead," you seem to be referring to the tensile force on the wire or
whatever material provides the reinforcement of the bead. Is that
correct?


Yes that's correct.
What I'd like to be able to predict is, given a tire's width
(cross-section area) and knowing an inflation pressure it should reach,
how much tensile strength do the beads need to have.


None. See my first reply.

* There is also the issue of the security of the interface

between rim and tire at the bead. Essentially, with a secure enough
bead "hook," the rim would serve in place of the tire bead.


Not with any modern tire. The only tires that were retained by a
hook-bead rim were the (cotton) cord-bead tires used previous to 1920 or
so at the latest.

One image, from 1913-http://www.norcom2000.com/users/dcimper/assorted/inanities/recumbent/...

I have not found anything written that indicated that the tiny ridges on
the edges of modern clincher bicycle tires plays any part in keeping
them on the rim.


Works with high pressures and flexible wires. Still has the problem
that upon deflation the tyre folds up.

* By way of

further example, a tubular tire requires nothing but the tire itself
(no extra circumferential reinforcement) to withstand applicable
pressures.


The physics of inflation pressure a tubular tire are considerably
different than a clincher.


Then you're looking at it wrong.

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