Re: Exploding tires II

Quoted message said:

Dear Jobst,

So what's an appropriate temperature?

I see numbers for grade, distance, speed, and tire pressure,
but nothing about what temperature you think would be
"appropriate."

If you're going to dismiss other posts for using an
"inappropriately low temperature," why not tell us what
temperature you have in mind?

I'd certainly be curious!

--
Frank Krygowski [To reply, remove rodent and vegetable dot com.
Substitute cc dot ysu dot
edu]

Quoted message said:

Carl Fogel said:

Elsewhere in this thread, someone suggested attaching some kind of
temperature-sensitive strips to the rim to show how hot they get. I
suppose that I'll have to pin my hopes on that approach.

I've done that and all the temperature spots turned from silver to
black, indicating that the strips don't go high enough and their
sensitivity to crude.

This was a red tape with silver spots calibrated in degrees. They
turn black when their temperature is reached. I did this long ago and
do not recall the name of the product or how high a temperature they
could read, only that they did not go high enough. Not much was
learned from this experiment.

Jobst Brandt
[email hidden]

Dear Jobst,

These modern temperature strips might be suitable, depending
on their length and width:

http://www.adamsintertech.com/MACH/PARTS/temp_strips.htm

They come in three ranges, from 250-320F, 290-360F, and
370-450F. Possibly they can be cut up and placed, piece by
piece, between spokes on a rim.

Regrettably, my daily ride offers no alpine descent to
justify buying a $22 40-strip pack. Maximum braking
yesterday was on flat pavement from about 20 mph to stop and
remove a box turtle from the path.

Carl Fogel

Mike Jacoubowsky said:

Quoted message said:

Did you try riding that wheel with the tire at 150psi? I suspect that
riding it on flatland, with no braking, that it would come off. I am
not convinced by a static test. Would you test ride that?

Not yet. What are the forces that would, without any braking action, cause
it to come off the rim while being ridden (but not otherwise)? We've
already been through threads explaining that there are virtually no "g
forces" exerted on tires (and thank goodness, since I wouldn't want to be
testing one for blowing off a rim while doing a slalom!).

But maybe I'm looking at the wrong thing. I keep thinking about what would
change in a tire or tube at higher temps that would cause one to blow off a
rim, but maybe it's not the tire that has trouble at (what I consider)
mildly-elevated pressures, but the rim? As pressure on the sides of the rim
increases (due to increasing tire pressure), the sides will bulge out
slightly. Perhaps enough to loosen their grip on the tire bead? And if
higher temperatures turn out to make the sidewall material more slippery?

FWIW, I just remembered a (possibly) related incident.

One summer day a few years ago, I had to drive to work, but I planned to
ride with a friend immediately after work. I had Avocet slicks on the bike.

The car was parked in the sun (don't recall the outside temperature).
When I finished work and drove to the friend's house, I pulled out a
bike with a blown back tire. Obviously, that tire'd blown off the rim
while the car was parked.

Air pressure would have been between 100 psi and 105 psi that morning.
Of course, I don't know the eventual air temperature inside the car. As
a guess, I'd assume the rear tire was partly in the sun as it came
through the rear window. I don't know if it was that part of the tire
that slipped off the rim, though.

What strikes me about this is: there was certainly a rise in
temperature, but I'm sure the rim didn't get anywhere near the boiling
point of water, let alone 500+ degrees. And there was no braking force
which might tend to cause any further shifting, creeping, etc. of the
tire on the rim. All that could have done it would be the (as we've
seen) moderate rise in air pressure, and the possible effects of
temperature on the rubber and other materials.

Unfortunately, it's a one-off "experiment." There is, I suppose, the
chance there was a unique problem with that tire, or its mounting
(although it had plenty of miles on it with no trouble).

If anyone wants to get experimental, they might take a wheel with a
well-mounted tire and pop it in the oven for a few hours!

And for a totally unrelated incident: I once blew a hole right in the
center of the tread of an expensive Clement Campianato Del Mundo Seta
(sp?) tubular, by leaving it parked in the Georgia summer sun. And it
wasn't even noon yet!

--
Frank Krygowski [To reply, remove rodent and vegetable dot com.
Substitute cc dot ysu dot
edu]

Alfred Ryder said:

Years ago, I had a Michelin tire that was too fat. It must have been
miss-labeled. I put it on the rear even though I knew it was
dangerously fat.

"Dangerously fat?" What is a "dangerously fat" bicycle tire? Bicycle
tires come in ranges from 3/4" to 3" in width. At what point is a
tire "dangerously fat?"

Quoted message said:

It gave no problem even when it got hot as long as I was moving at a
reasonable speed. But then, while it was hot, I stopped and sat at a
stoplight. And after a few seconds, it blew. I thought the world had
come to an end there for a half second or so.

How hot did your tire get? Was it smoking? And what got it so hot?

Quoted message said:

Is it possible that the bead got slippery with the heat and slid
out? Perhaps the weight I had on it while stopped pushed the bead
at the bottom of the wheel up so that it disengaged somewhere
else. Or perhaps my weight pushed the sidewall out where the tire
was in contact with the road enough so that the slippery bead slid
out from the hook of the rim. I don't remember where on the wheel
the tube was blown.

If the blowout somehow results from the bead getting soft and
slippery, blowouts from hot tires would occur when the rider was
either stopped or moving slowly enough for the bead to slide out of
the rim hook at the road contact area.

I'm sorry but this is just a goofy theory. The usual culprit in such
cases in that the inner tube was trapped between the bead and the rim.
Massive overheating, such as heavy braking on long twisty descents
such as Alpine mountain roads, can also cause blowouts from increased
air pressure in the tube- not slippery beads from getting hot.

"Tim McNamara" <[email hidden]> wrote in message
news:[email hidden]

Quoted message said:

Alfred Ryder said:

Years ago, I had a Michelin tire that was too fat. It must have been
miss-labeled. I put it on the rear even though I knew it was
dangerously fat.

"Dangerously fat?" What is a "dangerously fat" bicycle tire? Bicycle
tires come in ranges from 3/4" to 3" in width. At what point is a
tire "dangerously fat?"

http://www.sheldonbrown.com/tire-sizing.html#width

--

A: Top-posters.
Q: What is the most annoying thing on Usenet?

"Trevor" <[email hidden]> wrote in message
news:[email hidden]

Quoted message said:

[email hidden] wrote in message ...

Quoted message said:

Mike Jacoubowsky said:

That it happens isn't questionable. Why it happens is. A tire
ought to be able to handle a pretty significant amount of pressure
over what it's rated for. A typical tire will easily handle 150psi
before blowing off a rim (easily proven in the shop). But I'm not
seeing the physics (yet) that show a high-enough temperature
differential to accomplish this. That's why I'm thinking there's
more to it than just an increase in pressure.

Did you try riding that wheel with the tire at 150psi? I suspect
that riding it on flatland, with no braking, that it would come off.
I am not convinced by a static test. Would you test ride that?

So what pressure does a track cyclist use with 20mm high pressures?
I think it would be near 150psi in most cases.

FWIW, when Anna Meares was interviewed the other night at one point she said
she was running at 220psi, but obviously she was using tubulars.

--

A: Top-posters.
Q: What is the most annoying thing on Usenet?

[email hidden] wrote in message ...

Quoted message said:

dianne_1234567890? said:

Quoted message said:

>> I have seen a far greater number of tubes exhibiting
>> snake-bite-type damage (as you'd see on a compression cut) on
>> "blowouts" on steep descents, making me wonder if the material
>> properties of the rubber itself change (for the worse) as
>> temperatures rise.

Quoted message said:

Quoted message said:

> I wonder if the tube gets the snakebite cut after the blowout,
> before the rider comes to a stop?

Quoted message said:

Quoted message said:

That's a red herring! If the tire got a flat first, then what made
it blow off the rim and go BANG! This makes no sense.

Quoted message said:

Sorry, let me try to describe it differently: Maybe the tube gets
the snakebite cut *after* the blowout, while the rider rides on the
flat tire, the rim bumping along on the tire and tube, while slowing
to a stop?

Maybe, maybe the moon is made of green cheese... If the tire blows
off, you know about it. There is no doubt and the tube will have a
long slash. Why do you care if there are also snake bite holes? The
tube is dead. You've got to come up with a better scenario if you
want your original quarry to fly.

Which has nowt todo with the price of fish.

Trevor

Trevor said:

My suggestion is that the tyre creeps due to the braking force is valid, use
low pressure within the front tyre and brake down a 1 in 5 the tyre creeps
around the rim evident from the valve resting at a skew angle.

But the blow-offs being discussed have happened with pretty high
pressures in the tire. My experience with such a blow-off after
braking hard following a fast descent was that the valve stem
was still in the normal vertical orientation in the rim hole
and showed no signs of having been pulled around the rim.

I'd still be interested in what temperatures anyone has
measured using the color indicator dots.

Trevor said:

[email hidden] wrote in message ...

Quoted message said:

Mike Jacoubowsky said:

That it happens isn't questionable. Why it happens is. A tire
ought to be able to handle a pretty significant amount of pressure
over what it's rated for. A typical tire will easily handle 150psi
before blowing off a rim (easily proven in the shop). But I'm not
seeing the physics (yet) that show a high-enough temperature
differential to accomplish this. That's why I'm thinking there's
more to it than just an increase in pressure.

Did you try riding that wheel with the tire at 150psi? I suspect that
riding it on flatland, with no braking, that it would come off. I am
not convinced by a static test. Would you test ride that?

So what pressure does a track cyclist use with 20mm high pressures?
I think it would be near 150psi in most cases.

Trevor

Dear Trevor,

Few riders touring the Alps inflate their tires to 150 psi.

Carl Fogel

Quoted message said:

Mike Jacoubowsky said:

Quoted message said:

>Are you suspecting that the air temp in the tube actually exceeds
>100C? In the 0-100C example, the pressure differential didn't
>appear to be enough to blow a (properly mounted) tire off of a rim
>(from 100psi to 136psi).

Quoted message said:

Quoted message said:

That depends on how long the tube is exposed to how high a
temperature. What is proven is that you can blow a tire off the
rim with brake heating.

Quoted message said:

That it happens isn't questionable. Why it happens is. A tire
ought to be able to handle a pretty significant amount of pressure
over what it's rated for. A typical tire will easily handle 150psi
before blowing off a rim (easily proven in the shop). But I'm not
seeing the physics (yet) that show a high-enough temperature
differential to accomplish this. That's why I'm thinking there's
more to it than just an increase in pressure.

Did you try riding that wheel with the tire at 150psi? I suspect that
riding it on flatland, with no braking, that it would come off. I am
not convinced by a static test. Would you test ride that?

I have, and the tire didn't come off. I have a set of
Vredestein Fortezza Pista tires, which are spec.'ed with a
maximum pressure of 145 psi. When competing in time trials
of up to 40 km, I have been known to inflate them to maximum
pressure, or maybe a smidgen more. I also compete in roller
races where I inflate these tires to 160 psi. They are
mounted on a set of Campagnolo Shamal wheels. They have
never even given a hit of coming off.

Mark McMaster
[email hidden]

Frank Krygowski said:

Quoted message said:

Quoted message said:

Elsewhere in this thread, someone suggested attaching some kind of
temperature-sensitive strips to the rim to show how hot they
get. I suppose that I'll have to pin my hopes on that approach.

Quoted message said:

Quoted message said:

I've done that and all the temperature spots turned from silver to
black, indicating that the strips don't go high enough and their
sensitivity to crude.

Quoted message said:

Quoted message said:

This was a red tape with silver spots calibrated in degrees. They
turn black when their temperature is reached. I did this long ago
and do not recall the name of the product or how high a temperature
they could read, only that they did not go high enough. Not much
was learned from this experiment.

Quoted message said:

Maybe it's time for a rerun.

Quoted message said:

One brand of these is Tempilabel, and at least some of them read up
to 500 deg. F. That ought to cover things. See:

http://www.tempil.com/pdf/Tempilabel.pdf

Quoted message said:

or see Omega's offerings at:

http://www.omega.com/ppt/pptsc.asp?ref=TL-10

Quoted message said:

As an alternative, an infrared thermometer could be used.

http://www.omega.com/toc_asp/section.asp?book=temperature&section=j

If you've got one, make some measurements,

Quoted message said:

These are non-contact, and might even be rigged to get readings
while riding the bike. These things can measure up to the melting
temperature of aluminum, which is probably enough range.

How else do you measure infrared radiation it not optically.

Jobst Brandt
[email hidden]

Quoted message said:

Carl Fogel writes:

I've done that and all the temperature spots turned from silver to
black, indicating that the strips don't go high enough and their
sensitivity to crude.

This was a red tape with silver spots calibrated in degrees. They
turn black when their temperature is reached. I did this long ago and
do not recall the name of the product or how high a temperature they
could read, only that they did not go high enough. Not much was
learned from this experiment.

To avoid the crud, how about putting them inside the tire, under
the rim strip. It's a pain, but might work better.

Joe

Frank Krygowski said:

The car was parked in the sun (don't recall the outside temperature).
When I finished work and drove to the friend's house, I pulled out a
bike with a blown back tire. Obviously, that tire'd blown off the rim
while the car was parked.

Air pressure would have been between 100 psi and 105 psi that morning.
Of course, I don't know the eventual air temperature inside the car. As
a guess, I'd assume the rear tire was partly in the sun as it came
through the rear window. I don't know if it was that part of the tire
that slipped off the rim, though.

What strikes me about this is: there was certainly a rise in
temperature, but I'm sure the rim didn't get anywhere near the boiling
point of water, let alone 500+ degrees.

I left a candy thermometer in my car one sunny day. It reached just
over 200 degrees F.

I bought this thermometer at the grocery store. It wasn't expensive;
anyone who wants to know the temperature in their car should be able
to get one. They start at about $4.

http://froogle.google.com/froogle?q=candy%20thermometer&hl=en&lr=&ie=UTF-8&c2coff=1&safe=off&sa=N&tab=wf

or

http://tinyurl.com/5fvmf

Joe Riel said:

Quoted message said:

I've done that and all the temperature spots turned from silver to
black, indicating that the strips don't go high enough and their
sensitivity to crude.

Quoted message said:

Quoted message said:

This was a red tape with silver spots calibrated in degrees. They
turn black when their temperature is reached. I did this long ago and
do not recall the name of the product or how high a temperature they
could read, only that they did not go high enough. Not much was
learned from this experiment.

Quoted message said:

To avoid the crud, how about putting them inside the tire, under the
rim strip. It's a pain, but might work better.

Huh? What problem does this solve? What crud are you talking about?
And finally, "work better" than what?

Jobst Brandt
[email hidden]

Quoted message said:

Frank Krygowski said:

One brand of these is Tempilabel, and at least some of them read up
to 500 deg. F. That ought to cover things. See:

http://www.tempil.com/pdf/Tempilabel.pdf

Quoted message said:

or see Omega's offerings at:

http://www.omega.com/ppt/pptsc.asp?ref=TL-10

Quoted message said:

As an alternative, an infrared thermometer could be used.

http://www.omega.com/toc_asp/section.asp?book=temperature&section=j

If you've got one, make some measurements,

I've got access to one. What I lack is the mountain.

Quoted message said:

Quoted message said:

These are non-contact, and might even be rigged to get readings
while riding the bike. These things can measure up to the melting
temperature of aluminum, which is probably enough range.

How else do you measure infrared radiation it not optically.

??

--
--------------------+
Frank Krygowski [To reply, remove rodent and vegetable dot com,
replace with cc.ysu dot edu]

Trevor said:

[email hidden] wrote in message ...

Quoted message said:

Quoted message said:

Dear Trevor,

Since the tire's braking is confined to a small contact
patch, it seems unlikely that there is enough traction to
spin a normally inflated tire on its rim by braking.

There's about 160 linear inches of tire striping the insides
of the rim, perhaps a quarter of an inch wide, all under the
same pressure per square inch as the contact patch. That's
roughly 40 square inches versus one to two square inches of
contact patch.

The tire would skid under braking long before it began to
creep around the rim, barring impressive greasing. And on
dry pavement, you'd flip a normal bicycle before the front
tire began to skid.

My suggestion is that the tyre creeps due to the braking force is valid, use
low pressure within the front tyre and brake down a 1 in 5 the tyre creeps
around the rim evident from the valve resting at a skew angle. High
pressure makes tyres grip rim with a greater tenacity whether hp tyres or
tubulars. Certain rim/tyre combinations do not grip so well, and higher
pressure will lift the tyre so causing a blow-out. A good tyre/rim combo
with elevated pressure reduces this creep even with softening glue under
tubulars.

Trevor

Dear Trevor,

Where do you descend 20% grades?

How does the steepness of the grade increase the leverage of
the braking for causing the rim to creep inside the tire?

How low a tire pressure do you use? And why do you use it?

Is the tire in question a tubular? If so, is it creeping
because the glue is melting?

Curiously,

Carl Fogel

Frank Krygowski said:

...
The car was parked in the sun (don't recall the outside temperature).
When I finished work and drove to the friend's house, I pulled out a
bike with a blown back tire. Obviously, that tire'd blown off the rim
while the car was parked.

Air pressure would have been between 100 psi and 105 psi that morning.
Of course, I don't know the eventual air temperature inside the car. As
a guess, I'd assume the rear tire was partly in the sun as it came
through the rear window. I don't know if it was that part of the tire
that slipped off the rim, though.

What strikes me about this is: there was certainly a rise in
temperature, but I'm sure the rim didn't get anywhere near the boiling
point of water, let alone 500+ degrees. And there was no braking force
which might tend to cause any further shifting, creeping, etc. of the
tire on the rim. All that could have done it would be the (as we've
seen) moderate rise in air pressure, and the possible effects of
temperature on the rubber and other materials.

Further memory on that event: I just remembered that the tire was
ruined. As I recall, the bead wire was ripped away from the sidewall
for a few inches of circumference.

I know that typical blowoffs don't rip the tire this way. Still, I
wonder if this gives further evidence that the problem is related to the
effect of temperature on the materials. I think most of us agree it's
not simply high pressure doing the damage.

--
--------------------+
Frank Krygowski [To reply, remove rodent and vegetable dot com,
replace with cc.ysu dot edu]

Frank Krygowski said:

Quoted message said:

Frank Krygowski said:

One brand of these is Tempilabel, and at least some of them read up
to 500 deg. F. That ought to cover things. See:

http://www.tempil.com/pdf/Tempilabel.pdf

Quoted message said:

or see Omega's offerings at:

http://www.omega.com/ppt/pptsc.asp?ref=TL-10

Quoted message said:

As an alternative, an infrared thermometer could be used.

http://www.omega.com/toc_asp/section.asp?book=temperature&section=j
If you've got one, make some measurements,

I've got access to one. What I lack is the mountain.

Quoted message said:

Quoted message said:

These are non-contact, and might even be rigged to get readings
while riding the bike. These things can measure up to the melting
temperature of aluminum, which is probably enough range.

How else do you measure infrared radiation it not optically.

I just ran accross this:

http://www.bicyclesource.com/bike/choosing/brakes-paper.shtml

The page mentions that "oven tests" for rim brakes were being proposed
by the CPSC in the 70s. Anyone know anything about this?

Quoted message said:

Probably an easy way to generate a colored puff would be with colored
chalk dust in the inner tube--no water needed. You might need a fair
amount to make sure the cloud is visible.

Umm... the idea was to produce the dramatic effect... safely. The chalk
dust in the inner tube doesn't show up until you've reached, ahem, terminal
velocity, and life is passing by a whole lot faster than you'd like.

The steaming rim effect occurs simply when things get hot, not when they
fail.

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com

"B.B." <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

In article <[email hidden]>,
"Mike Jacoubowsky/Chain Reaction Bicycles" <[email hidden]>

Quoted message said:

I knew that Skywriting planes trail smoke, but figured there must be
something that could be added to water that would evaporate and leave a
colored trail of some kind. But of course, if there was, you would just
use
that and not water, right? So the question becomes what boils at a
relevant
temperature and trails darkly-colored smoke.

Probably an easy way to generate a colored puff would be with colored
chalk dust in the inner tube--no water needed. You might need a fair
amount to make sure the cloud is visible.

--
B.B. --I am not a goat! thegoat4 at airmail.net

DRS said:

"Tim McNamara" <[email hidden]> wrote in message
news:[email hidden]

Quoted message said:

Alfred Ryder said:

Years ago, I had a Michelin tire that was too fat. It must have
been miss-labeled. I put it on the rear even though I knew it was
dangerously fat.

"Dangerously fat?" What is a "dangerously fat" bicycle tire?
Bicycle tires come in ranges from 3/4" to 3" in width. At what
point is a tire "dangerously fat?"

http://www.sheldonbrown.com/tire-sizing.html#width

Hmmm. I see no "dangerously fat" on that page. A reference to sloppy
handling and one odd claim that fat tires may cause rim failure. Not
sure what the mechanics of that are supposed to be, although Sheldon
is normally very very reliable in his information. The risk of
chafing the sidewall when using a fat tire and narrow rim has been
long known, although I've never seen it happen even using 32 mm tires
on 19 mm rims. Perhaps this is only an issue with low prssure tires.