Tire-making: bead stress, tire width, math, woe........

DougC wrote:
On 8/31/2011 4:21 PM, AMuzi wrote:


If I might make a conjecture, material suitable for a straight side rim
tire bead should be completely suitable to a hook edge rim (if not
overkill).

Yea I see that,,,, but then, if the straight-side bead must be
sustaining the pneumatic load, that thin of a wire bead shouldn't be
strong enough (according to the method of figuring the pneumatic load
that I used).

So then it appears that the rim wall friction plays a role in both
instances.

I had a new tyre blow off the rim that I'm sure was seated properly. I
had just prior washed the bike, and I suspect soapy water got into the
rim cavity, and then when I took the old tyre off, some got onto the
inner surface where the new tyre was seated. BOOM! Remove, clean, dry,
new tube, try again - success.

I've also seen a bloke pop his tyre off the rim twice in one wet ride.
Combination of water and a little too much pressure, IMHO.

I'd say friction plays a part.

--
JS.

James wrote:
DougC wrote:
On 8/31/2011 4:21 PM, AMuzi wrote:


If I might make a conjecture, material suitable for a straight side rim
tire bead should be completely suitable to a hook edge rim (if not
overkill).

Yea I see that,,,, but then, if the straight-side bead must be
sustaining the pneumatic load, that thin of a wire bead shouldn't be
strong enough (according to the method of figuring the pneumatic load
that I used).

So then it appears that the rim wall friction plays a role in both
instances.

I had a new tyre blow off the rim that I'm sure was seated properly. I
had just prior washed the bike, and I suspect soapy water got into the
rim cavity, and then when I took the old tyre off, some got onto the
inner surface where the new tyre was seated. BOOM! Remove, clean, dry,
new tube, try again - success.

I've also seen a bloke pop his tyre off the rim twice in one wet ride.
Combination of water and a little too much pressure, IMHO.

I'd say friction plays a part.


Although I believe you that it happened, the cause is not
water per se.

Car and truck tires are commonly mounted with soapy water or
a similar seating solution, Bicycle tires, especially
straight side steel rims, are commonly mounted with spray
wax or similar. In both cases the idea is to get the entire
bead on the rim bead seat evenly before full pressure. One
difference is that a bicycle tire blowing off a rim may wake
you but a car tire can blind or kill you. 'Problem' rims get
more seating solution, not less. At the other extreme, a
Scirocco wheel with a Michelin Pro doesn't need any help.
Michelins seat promptly with a loud snap on any quality rim.

An improperly seated tire can and eventually probably will
go sailing off a rim. Water cannot possibly penetrate
between the rim and a seated bicycle tire at any reasonable
pressure. All bicycle tires have a molded line which should
be observed, evenly spaced above the brake track, before
full inflation. A brief void, where that line is below the
rim edge, is preface to a blown off tire because some other
part of the bead is not on its seat.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

AMuzi wrote:
James wrote:
DougC wrote:
On 8/31/2011 4:21 PM, AMuzi wrote:


If I might make a conjecture, material suitable for a straight side rim
tire bead should be completely suitable to a hook edge rim (if not
overkill).

Yea I see that,,,, but then, if the straight-side bead must be
sustaining the pneumatic load, that thin of a wire bead shouldn't be
strong enough (according to the method of figuring the pneumatic load
that I used).

So then it appears that the rim wall friction plays a role in both
instances.

I had a new tyre blow off the rim that I'm sure was seated properly.
I had just prior washed the bike, and I suspect soapy water got into
the rim cavity, and then when I took the old tyre off, some got onto
the inner surface where the new tyre was seated. BOOM! Remove,
clean, dry, new tube, try again - success.

I've also seen a bloke pop his tyre off the rim twice in one wet ride.
Combination of water and a little too much pressure, IMHO.

I'd say friction plays a part.


Although I believe you that it happened, the cause is not water per se.

Car and truck tires are commonly mounted with soapy water or a similar
seating solution,

And are generally inflated to less than half the pressure with a much
larger contact area. I would have difficulty pushing a car tyre on with
out tools.

Bicycle tires, especially straight side steel rims,
are commonly mounted with spray wax or similar. In both cases the idea
is to get the entire bead on the rim bead seat evenly before full
pressure.

Which may be why I had one blow off. It is possible too, that one part
was lubed with soapy water while another was not.

One difference is that a bicycle tire blowing off a rim may
wake you but a car tire can blind or kill you. 'Problem' rims get more
seating solution, not less. At the other extreme, a Scirocco wheel with
a Michelin Pro doesn't need any help. Michelins seat promptly with a
loud snap on any quality rim.

Yep, I get that with my quality Ksyrium rims. Must be part of the EH&M ;-)

An improperly seated tire can and eventually probably will go sailing
off a rim. Water cannot possibly penetrate between the rim and a seated
bicycle tire at any reasonable pressure.

Totally agree.

All bicycle tires have a
molded line which should be observed, evenly spaced above the brake
track, before full inflation. A brief void, where that line is below the
rim edge, is preface to a blown off tire because some other part of the
bead is not on its seat.

I suppose it is possible that partial lube may allow a portion to get to
the seat before another, and encourage an imbalance.

--
JS

On Aug 31, 4:04*pm, DougC wrote:
On 8/31/2011 4:21 PM, AMuzi wrote:



If I might make a conjecture, material suitable for a straight side rim
tire bead should be completely suitable to a hook edge rim (if not
overkill).

Yea I see that,,,, but then, if the straight-side bead must be
sustaining the pneumatic load, that thin of a wire bead shouldn't be
strong enough (according to the method of figuring the pneumatic load
that I used).

So then it appears that the rim wall friction plays a role in both
instances.



The inverse is not always true, as Aramid bead tires on ancient straight
side rims show.

I'm not arguing with your observations, but I said why that would be
wrong. An aramid twine of a given diameter is very close in strength to
what a similar-size piece of steel cable would be,,, only maybe 3% less
strong than the steel.

It don't make no sense?!?!?

For a given diameter, aramid is, as you say, nearly equivalent in
tensile strength to steel. Hence it will BREAK under roughly the same
force.
BUT prior to breaking, it will stretch roughly twice as much as steel
under any given load.

DR

On 8/22/2011 8:37 PM, john B. wrote:
[...]
Errr... there is no "beam" involved in tire strength.
[...]

Yes, he left the newsgroup about a year ago.

--
Tºm Shermªn - 42.435731°N, 83.985007°W
I am a vehicular cyclist.

On 8/23/2011 9:31 AM, thirty-six wrote:
[...]
In time I gained the knowledge that tubulars were lighter, offered
less rolling resistance, more speed, greater cornering forces and were
also foldable and didn't need space age technology to support a
misconstrued construction method encouraged by patent chasing. They
were already pretty much at their zenith, only the funding was short
to obtain the best.[...]

Plus the opportunity to sniff the glue, eh?

--
Tºm Shermªn - 42.435731°N, 83.985007°W
I am a vehicular cyclist.

On Sep 9, 4:05*am, "T°m Sherm@n" ""twshermanREMOVE\"@THI
$southslope.net" wrote:
On 8/23/2011 9:31 AM, thirty-six wrote:
* [...]

In time I gained the knowledge that tubulars were lighter, offered
less rolling resistance, more speed, greater cornering forces and were
also foldable and didn't need space age technology to support a
misconstrued construction method encouraged by patent chasing. *They
were already pretty much at their zenith, only the funding was short
to obtain the best.[...]

Plus the opportunity to sniff the glue, eh?

--
Tºm Shermªn - 42.435731°N, 83.985007°W
I am a vehicular cyclist.

Isn't it past your bed-time?

On Aug 22, 5:47*pm, DougC wrote:
I'm wondering if it is possible that a rough estimate of necessary bead
strength could be determined for a given size tire. There is info online
about figuring wall strength of hoses and cylinders containing pressure,
but they don't deal with the situation of a tire--where the wall is
interrupted.

I've cut up a couple cheap cruiser tires and seen that for them (about
2.1" wide, with a max pressure of 40 PSI) that each of the beads is a
piece of cable with a total breaking strength of about 300 lbs. I could
just match that (even cheap tire beads very rarely fail at their rated
pressures) but it would be nice to know a rule of thumb when making
different-size tires.

*From what I have seen of tires I have on hand, the tire's overall
diameter has very little if anything to do with bead loads. I have a
pair of 1.5" wide Kenda Kwest 100 psi tires in 406mm and 559mm, and both
have the same width casings, and both beads measure right about the same
thickness (.118").

{-I am just measuring on the outside of the tire bead, rubber and all,
but anyway}

I also have a 2.3" 559 Big Apple (60 psi), and it is about 6.5" across
the casing, and the beads of it measure right about .150". The BA beads
feel quite stiffer than the Kwests as well.

So then-

1) assuming they have the same cross-section, a larger-diameter tire
(26") does not seen to need a thicker bead than a smaller-diameter tire
(20")

2) the overall tire pressure does necessitate a stronger bead as the
tire pressure increases, but-

3) the stress on the bead increases with the tire's cross-section more
than it does for the pressure (the BA's pressure is only 60% of the
Kwests, but the BA bead is still considerably thicker)

4) I am also wondering now what difference in rim width would make, as
you can get road 26" rims that are ~25mm wide, as well as cruiser 26"
rims that are 80mm wide. On the 80mm rim, not only does the tire's
internal volume increase, but the portion borne by the beads increases
as well.

Is this a problem that can even be estimated roughly, or would it
require 3-d modeling to figure out? It would seem to be fairly simple,
as the tire casing always expands into a circle (the cross-section of
the tire, that is...).

* ----------

Also when I went looking for such info online, I ran across a lot of
reports of people trying to use non-tubeless tires on tubeless rims.

It's pretty surprising (to me) how common it is for people to say that
the tubeless setups ride much better, but also how common the problem is
of a tire blowing off a tubeless rim and the bead being permanently
damaged from it (ruining the tire). Usually this seems to be with tires
that are not intended for tubeless use; I've already read that a lot of
tires not specified as tubeless are not warrantied for this purpose.

I've never seen these IRL as the first one came out right as I got rid
of the last MTB I had. I've already read a lot of accounts of it, but if
there's any websites that have a lot of pictures and explanations of the
different rims it'd be interesting to see.


Both whitewall and white treads under $30 . Are you sure you want to
continue?
http://store.electrabike.com/eSource...V2.aspx?store=

On 9/10/2011 9:59 PM, thirty-six wrote:
....


Both whitewall and white treads under $30 . Are you sure you want to
continue?
http://store.electrabike.com/eSource...V2.aspx?store=

Neither of those tires is a vintage style at all.

The white-rubber tire is not a period tread, and even the whitewall
coloring is done wrong--even if you ignore the non-period tread.

Other than slicks, the earliest treads available on bicycle tires now
date from the 1930's. That would be ones like the Cheng Shin C241--which
incidentally, the Electra Strat-O-Balloon tires use,,, but there was
pneumatic tires for 30 years before that.

Plus, as I said--there are other possibilities, aside from just using
pretty colors and old tread styles.