tire punctures and tire pressure- relation?

This is so hard to do science on 'cause the real differences show up when size goes up and
pressure, down. Problem is larger tires have thicker tread-skewed results. Anecdotally, when I
worry about flats, but want more speed than the ruffy tuffies provide, the 25mm (actual26) mich pro
race wins. Tom

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

Quoted message said:

I got my first flat in almost a year today. I had just put 80 PSI in
tires I usually run at 60-70 PSI. This made me wonder if there is
any correlation between the air pressure in a tire and its
susceptibility to puncture flats (not that this would explain my flat-
a triangular metal shard driven straight into the rubber that most
likely would have punctured at almost any PSI).

But it got me thinking- do higher pressures in tires make them more
susceptible to punctures? Is there anything about the 'stiffer' tire
at higher pressures that makes it less flexible *and* allows objects
to puncture? Do lower PSIs make a tire's contact patch more flexible
and able to roll over objects rather than have them puncture? Does
pressure have no effect on some type of puncture objects and some
effect on other puncture objects? Just curious.

On Thu, 15 Jan 2004 23:28:02 -0800, Dan Daniel

may have said:

But it got me thinking- do higher pressures in tires make them more susceptible to punctures? Is
there anything about the 'stiffer' tire at higher pressures that makes it less flexible *and*
allows objects to puncture? Do lower PSIs make a tire's contact patch more flexible and able to
roll over objects rather than have them puncture? Does pressure have no effect on some type of
puncture objects and some effect on other puncture objects? Just curious.

I know of only one direct relation between pressure and puncture resistance; the lower the tire
pressure, the greater the risk of "snakebite" flats caused by the tube getting pinched when the
tire's pressure was insufficient.

Beyond that, I'm not sure there's any quantifiable general connection.

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Dan Daniel said:

I got my first flat in almost a year today. I had just put 80 PSI in tires I usually run at 60-70
PSI. This made me wonder if there is any correlation between the air pressure in a tire and its
susceptibility to puncture flats (not that this would explain my flat- a triangular metal shard
driven straight into the rubber that most likely would have punctured at almost any PSI).

But it got me thinking- do higher pressures in tires make them more susceptible to punctures? Is
there anything about the 'stiffer' tire at higher pressures that makes it less flexible *and*
allows objects to puncture? Do lower PSIs make a tire's contact patch more flexible and able to
roll over objects rather than have them puncture? Does pressure have no effect on some type of
puncture objects and some effect on other puncture objects? Just curious.

Tends to be the other way round, and I think you were just unlucky. Higher pressures mean fewer
punctures as potential puncture-causing objects are more likely to be crushed or ejected. Two big
factors contributing to punctures (apart from the number of thorns on the road) are insufficient
pressure and wet weather. It's not just Sod's Law that dictates you will more often puncture when
it's raining. The sharp objects can penetrate rubber more easily when they're lubricated by water.

Experienced cyclists also get *far* fewer punctures than new cyclists. They pick better lines on
dirty roads and avoid the gutter on main streets.

Dan Daniel <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

I got my first flat in almost a year today. I had just put 80 PSI in tires I usually run at 60-70
PSI. This made me wonder if there is any correlation between the air pressure in a tire and its
susceptibility to puncture flats (not that this would explain my flat- a triangular metal shard
driven straight into the rubber that most likely would have punctured at almost any PSI).

But it got me thinking- do higher pressures in tires make them more susceptible to punctures? Is
there anything about the 'stiffer' tire at higher pressures that makes it less flexible *and*
allows objects to puncture? Do lower PSIs make a tire's contact patch more flexible and able to
roll over objects rather than have them puncture? Does pressure have no effect on some type of
puncture objects and some effect on other puncture objects? Just curious.

Dear Dan,

I'm curious, too.

Could this be what you have in mind?

Roll a tire across a knife-blade object, something wide and sharp. Given the same load, at lower
speeds and with lower tire pressures, the tire may deform, "tenting" over the blade. But if we
increase the speed or the tire pressure or both, then the blade cuts into the tire.

The same kind of "tenting" might occur when we roll over a spike.

But at normal speeds, loads, and tire pressures, I suspect that most things like thorns,
Michelin wires, sharp-edged glass slivers, fish-hooks, tacks, and similar debris will just
pierce the tire and tube.

Carl Fogel

[email hidden] (Carl Fogel) wrote in message news:<[email hidden]>...

Quoted message said:

Dan Daniel <[email hidden]> wrote in message
news:<[email hidden]>...

Quoted message said:

I got my first flat in almost a year today. I had just put 80 PSI in tires I usually run at 60-
70 PSI. This made me wonder if there is any correlation between the air pressure in a tire and
its susceptibility to puncture flats (not that this would explain my flat- a triangular metal
shard driven straight into the rubber that most likely would have punctured at almost any PSI).

But it got me thinking- do higher pressures in tires make them more susceptible to punctures? Is
there anything about the 'stiffer' tire at higher pressures that makes it less flexible *and*
allows objects to puncture? Do lower PSIs make a tire's contact patch more flexible and able to
roll over objects rather than have them puncture? Does pressure have no effect on some type of
puncture objects and some effect on other puncture objects? Just curious.

Dear Dan,

I'm curious, too.

Could this be what you have in mind?

Roll a tire across a knife-blade object, something wide and sharp. Given the same load, at lower
speeds and with lower tire pressures, the tire may deform, "tenting" over the blade. But if we
increase the speed or the tire pressure or both, then the blade cuts into the tire.

The same kind of "tenting" might occur when we roll over a spike.

But at normal speeds, loads, and tire pressures, I suspect that most things like thorns, Michelin
wires, sharp-edged glass slivers, fish-hooks, tacks, and similar debris will just pierce the tire
and tube.

Carl Fogel

Sure what happens is the rubber is under tension the tension will pull the tire apart allowing the
object to cut deeper. I get about 300 miles from a 27x1 1/4 tire on the rear or about 500 miles from
a 26x1.5 or about 2500 miles from a 26x1.5 kevlar tire with 165 lbs on the rear wheel they all fail
from glass cuts.

On 16 Jan 2004 11:37:33 -0800, [email hidden] (Carl Fogel)

Quoted message said:

Dan Daniel <[email hidden]> wrote in message
news:<[email hidden]>...

Quoted message said:

I got my first flat in almost a year today. I had just put 80 PSI in tires I usually run at 60-70
PSI. This made me wonder if there is any correlation between the air pressure in a tire and its
susceptibility to puncture flats (not that this would explain my flat- a triangular metal shard
driven straight into the rubber that most likely would have punctured at almost any PSI).

But it got me thinking- do higher pressures in tires make them more susceptible to punctures? Is
there anything about the 'stiffer' tire at higher pressures that makes it less flexible *and*
allows objects to puncture? Do lower PSIs make a tire's contact patch more flexible and able to
roll over objects rather than have them puncture? Does pressure have no effect on some type of
puncture objects and some effect on other puncture objects? Just curious.

Dear Dan,

I'm curious, too.

Could this be what you have in mind?

Roll a tire across a knife-blade object, something wide and sharp. Given the same load, at lower
speeds and with lower tire pressures, the tire may deform, "tenting" over the blade. But if we
increase the speed or the tire pressure or both, then the blade cuts into the tire.

The same kind of "tenting" might occur when we roll over a spike.

Yeah, these are the basic ideas I am curious about.

Quoted message said:

But at normal speeds, loads, and tire pressures, I suspect that most things like thorns, Michelin
wires, sharp-edged glass slivers, fish-hooks, tacks, and similar debris will just pierce the tire
and tube.

Carl Fogel

I am heading this way myself. For the 'tenting' that you speak of to occur, the tire might need to
be at such a significantly lower pressure that pinch flats and ruined tires from riding on the rim
would result.

Oh well, just one of those random thoughts and random ideas on my part. No real facts from me here.
I raised my tire pressure and got a flat which got me thinking, but coincidence is not the same as
correlation.

Werehatrack said:

Dan Daniel may have said:

But it got me thinking- do higher pressures in tires make them more susceptible to punctures? Is
there anything about the 'stiffer' tire at higher pressures that makes it less flexible *and*
allows objects to puncture? Do lower PSIs make a tire's contact patch more flexible and able to
roll over objects rather than have them puncture? Does pressure have no effect on some type of
puncture objects and some effect on other puncture objects? Just curious.

I know of only one direct relation between pressure and puncture resistance; the lower the tire
pressure, the greater the risk of "snakebite" flats caused by the tube getting pinched when the
tire's pressure was insufficient.

I used 'puncture' to try to separate it from pinch flats. I don't think of pinch flats as puncture
flats, but then again I don't know what word would work for them.

Quoted message said:

Beyond that, I'm not sure there's any quantifiable general connection.

Yeah, I'm heading that way. I am wondering if the effect I am thinking of would happen only at
extreme underinflation- so maybe minimal punctures because the tire is so soft, but then you'd ruin
the tube, tire and maybe even rim by riding on an almost empty tube.

On Fri, 16 Jan 2004 18:37:03 +0000, Zog The Undeniable <[email hidden]>

Quoted message said:

Dan Daniel said:

But it got me thinking- do higher pressures in tires make them more susceptible to punctures? Is
there anything about the 'stiffer' tire at higher pressures that makes it less flexible *and*
allows objects to puncture? Do lower PSIs make a tire's contact patch more flexible and able to
roll over objects rather than have them puncture? Does pressure have no effect on some type of
puncture objects and some effect on other puncture objects? Just curious.

Tends to be the other way round, and I think you were just unlucky. Higher pressures mean fewer
punctures as potential puncture-causing objects are more likely to be crushed or ejected.

? I don't understand what you mean here.

Quoted message said:

Two big factors contributing to punctures (apart from the number of thorns on the road) are
insufficient pressure and wet weather. It's not just Sod's Law that dictates you will more often
puncture when it's raining. The sharp objects can penetrate rubber more easily when they're
lubricated by water.

Then again, many people lower their tire pressure in the rain. I do. Maybe some strange idea on my
part that a softer tire will not puncture as easily?

Quoted message said:

Experienced cyclists also get *far* fewer punctures than new cyclists. They pick better lines on
dirty roads and avoid the gutter on main streets.

This is also why that flat yesterday stuck with me. I get them so rarely, I wind up thinking about
them far too much. Well, the flat and a couple of other recent riding events on my commutes and
trips around the city might be mainly a wake-up call for to stop daydreaming on the bike.

Dan Daniel said:

Zog The Undeniable said:

Dan Daniel said:

But it got me thinking- do higher pressures in tires make them more susceptible to punctures? Is
there anything about the 'stiffer' tire at higher pressures that makes it less flexible *and*
allows objects to puncture? Do lower PSIs make a tire's contact patch more flexible and able to
roll over objects rather than have them puncture? Does pressure have no effect on some type of
puncture objects and some effect on other puncture objects? Just curious.

Tends to be the other way round, and I think you were just unlucky. Higher pressures mean fewer
punctures as potential puncture-causing objects are more likely to be crushed or ejected.

? I don't understand what you mean here.

Quoted message said:

Two big factors contributing to punctures (apart from the number of thorns on the road) are
insufficient pressure and wet weather. It's not just Sod's Law that dictates you will more often
puncture when it's raining. The sharp objects can penetrate rubber more easily when they're
lubricated by water.

Then again, many people lower their tire pressure in the rain. I do. Maybe some strange idea on my
part that a softer tire will not puncture as easily?

Quoted message said:

Experienced cyclists also get *far* fewer punctures than new cyclists. They pick better lines on
dirty roads and avoid the gutter on main streets.

This is also why that flat yesterday stuck with me. I get them so rarely, I wind up thinking about
them far too much. Well, the flat and a couple of other recent riding events on my commutes and
trips around the city might be mainly a wake-up call for to stop daydreaming on the bike.

The pressure between the tyre and ground is obviously the same as the pressure in the tyre.
Something at 100psi stands more chance of crushing a thorn [1] than something at 50psi. The contact
patch being smaller also means you're less likely to hit any given object in the first place.

[1] the usual cause of punctures round here, especially just after the hedge-trimmers have been out.

Dan Daniel said:

... Oh well, just one of those random thoughts and random ideas on my part. No real facts from me
here. I raised my tire pressure and got a flat which got me thinking, but coincidence is not the
same as correlation.

And correlation is not the same as causal relationship.

Tom Sherman - Quad Cities