Tire puzzle

In article
,
Chalo wrote:

Michael Press wrote:

*Art Harris wrote:

Leo Lichtman wrote:

Your information is incorrect. *A wider tire will have *increased* rolling
resistance. *

Is that true? I always thought that everything else being equal
(including pressure), a wider tire would have less rolling resistance.

Rolling resistance arises from flexing of the casing and tread.
Thinner casing means less rolling resistance.
Thinner tread and less tread pattern means less rolling resistance.

Larger width tire means the rubber and casing distort less (change
less in curvature and therefore in strain) to establish a contact
patch, even at proportionally lower pressure. It is not just the
amount of tread material being strained, but also the degree to which
it is strained that determines how much energy is lost to heat.

Yes. What is the relationship between
membrane thickness and energy required to flex it?


As the tire gets wider the physics of pressure vessels demands
that the tire casing be stronger in tension. This means that
wider tires must be made with thicker, less flexible, more
power consuming casings than thinner tires.

And they distort less at the contact patch. And when they are lower
in pressure and more compliant, they make the bike and rider rise and
fall through shorter displacements and more gradually, reducing
hysteresis losses in the rider.

How much less does a wide tire deflect?
The contact patch is larger,
so the perimeter of the contact patch is longer,
so the area of greatest curvature is larger.

In all the discussions here I have never heard a persuasive
argument detailing the factors that work in the direction
wider tire - reduced rolling resistance.

I have ridden on city streets on a bare steel rim, which has much less
rolling resistance than any rubber tire. In spite of this, I can
assure you that it is slower than using a tire.

http://www.morrispost.com/rimridep.htm

--
Michael Press

Michael Press wrote:

*Chalo wrote:

Michael Press wrote:

As the tire gets wider the physics of pressure vessels demands
that the tire casing be stronger in tension. This means that
wider tires must be made with thicker, less flexible, more
power consuming casings than thinner tires.

And they distort less at the contact patch. *And when they are lower
in pressure and more compliant, they make the bike and rider rise and
fall through shorter displacements and more gradually, reducing
hysteresis losses in the rider.

How much less does a wide tire deflect?
The contact patch is larger,
so the perimeter of the contact patch is longer,
so the area of greatest curvature is larger.

A wider tire has a flatter angle of incidence at the contact patch,
hence less strain in the tread and casing there. Deflecting a large
casing at e.g. a 20 degree angle from the tangent, as in a balloon
tire, takes less work than deflecting a narrow casing at e.g. a 90
degree angle from the tangent, as in a narrow racing tire supporting
the same load (given directly comparable construction).

Why? Hysteresis loss in rubber is characterized as proportional to
the square of the strain. The perimeter length of the contact patch
is proportional to the _square root_ of the contact patch's area.
Make a tire narrower, and its rubber strain at the contact patch
increases disproportionately, while the perimeter length of its
contact patch changes by only a relatively small amount.

If the tires are of identical tread and similar casing strength _with
respect to their properly inflated casing hoop stress_, then the one
that contacts the ground more tangentially will have less internal
loss under load, at the same load.

It's not the nature of wide tires to have higher internal losses.
Rather it's the nature of the market for wide tires to favor
durability and puncture resistance, and these tend to add rolling
resistance.

Chalo

On Mar 11, 6:47 pm, Chalo wrote:
Michael Press wrote:

Chalo wrote:

Michael Press wrote:

As the tire gets wider the physics of pressure vessels demands
that the tire casing be stronger in tension. This means that
wider tires must be made with thicker, less flexible, more
power consuming casings than thinner tires.

And they distort less at the contact patch. And when they are lower
in pressure and more compliant, they make the bike and rider rise and
fall through shorter displacements and more gradually, reducing
hysteresis losses in the rider.

How much less does a wide tire deflect?
The contact patch is larger,
so the perimeter of the contact patch is longer,
so the area of greatest curvature is larger.

A wider tire has a flatter angle of incidence at the contact patch,
hence less strain in the tread and casing there. Deflecting a large
casing at e.g. a 20 degree angle from the tangent, as in a balloon
tire, takes less work than deflecting a narrow casing at e.g. a 90
degree angle from the tangent, as in a narrow racing tire supporting
the same load (given directly comparable construction).

Why? Hysteresis loss in rubber is characterized as proportional to
the square of the strain. The perimeter length of the contact patch
is proportional to the _square root_ of the contact patch's area.
Make a tire narrower, and its rubber strain at the contact patch
increases disproportionately, while the perimeter length of its
contact patch changes by only a relatively small amount.

If the tires are of identical tread and similar casing strength _with
respect to their properly inflated casing hoop stress_, then the one
that contacts the ground more tangentially will have less internal
loss under load, at the same load.

It's not the nature of wide tires to have higher internal losses.
Rather it's the nature of the market for wide tires to favor
durability and puncture resistance, and these tend to add rolling
resistance.

Chalo

Bravo;

Best-written post (in English) on the topic in years.

Harry Travis

On Mar 11, 11:54*pm, incredulous 2 wrote:
On Mar 11, 6:47 pm, Chalo wrote:





Michael Press wrote:

*Chalo wrote:

Michael Press wrote:

As the tire gets wider the physics of pressure vessels demands
that the tire casing be stronger in tension. This means that
wider tires must be made with thicker, less flexible, more
power consuming casings than thinner tires.

And they distort less at the contact patch. *And when they are lower
in pressure and more compliant, they make the bike and rider rise and
fall through shorter displacements and more gradually, reducing
hysteresis losses in the rider.

How much less does a wide tire deflect?
The contact patch is larger,
so the perimeter of the contact patch is longer,
so the area of greatest curvature is larger.

A wider tire has a flatter angle of incidence at the contact patch,
hence less strain in the tread and casing there. *Deflecting a large
casing at e.g. a 20 degree angle from the tangent, as in a balloon
tire, takes less work than deflecting a narrow casing at e.g. a 90
degree angle from the tangent, as in a narrow racing tire supporting
the same load (given directly comparable construction).

Why? *Hysteresis loss in rubber is characterized as proportional to
the square of the strain. *The perimeter length of the contact patch
is proportional to the _square root_ of the contact patch's area.
Make a tire narrower, and its rubber strain at the contact patch
increases disproportionately, while the perimeter length of its
contact patch changes by only a relatively small amount.

If the tires are of identical tread and similar casing strength _with
respect to their properly inflated casing hoop stress_, then the one
that contacts the ground more tangentially will have less internal
loss under load, at the same load.

It's not the nature of wide tires to have higher internal losses.
Rather it's the nature of the market for wide tires to favor
durability and puncture resistance, and these tend to add rolling
resistance.

Chalo

Bravo;

Best-written post (in English) on the topic in years.

Harry Travis- Hide quoted text -

- Show quoted text -

thanks ! we respect the literate.
not much
but feel free posting

In article ,
Michael Press wrote:

In article
,
Art Harris wrote:

Leo Lichtman wrote:
Your information is incorrect. *A wider tire will have
*increased* rolling resistance. *


Is that true? I always thought that everything else being equal
(including pressure), a wider tire would have less rolling
resistance.

Rolling resistance arises from flexing of the casing and tread.
Thinner casing means less rolling resistance. Thinner tread and less
tread pattern means less rolling resistance. As the tire gets wider
the physics of pressure vessels demands that the tire casing be
stronger in tension. This means that wider tires must be made with
thicker, less flexible, more power consuming casings than thinner
tires.

In all the discussions here I have never heard a persuasive argument
detailing the factors that work in the direction wider tire -
reduced rolling resistance.

There have been comparative measurements of the phenomenon published in
Tour Magazine, among other places. Since there are some tires of
varying width with otherwise identical construction (e.g., Michelin Pro
Race), the phenomenon has been measured and confirmed. The differences
are not huge, however.

The problem, of course, is that it's hard to compare apples and apples.
Wider tires often have thicker rubber and more pronounced tread
patterns. I think you mentioned this in another post.

In threads a few years back in connection with the IRC tire tests of
yore, Jobst commented on the issue you bring up about casing thickness.
IIRC he said that the break point between being able to use lighter 127
tpi fabric and heavier 66 tpi fabric was around 25-26 mm; tires fatter
than this require the heavier casing due to higher casing tension.
IMNRC.

There have recently been some tires brought to market that are markedly
wider (e.g., 30 mm) under the Grand Bois label; these are supposed to
have very light casings and thin tread (to lower rolling resistance) and
as a result have a lower maximum inflation pressure than we have come to
think of as normal. I have seen no independent measurements of these
tires, though, and have no idea if the theory bears fruit at larger
sizes or if the thicker casing trumps whatever benefit the wider tire
might have. Jan Heine found the old fat Clement Campionato del Mundos
to be among the fastest tires they tested in their roll-down tests; the
fastest was a 24 mm clincher (Deda Tre- something or other).

On 12 Mar, 03:54, incredulous 2 wrote:
On Mar 11, 6:47 pm, Chalo wrote:



Michael Press wrote:

*Chalo wrote:

Michael Press wrote:

As the tire gets wider the physics of pressure vessels demands
that the tire casing be stronger in tension. This means that
wider tires must be made with thicker, less flexible, more
power consuming casings than thinner tires.

And they distort less at the contact patch. *And when they are lower
in pressure and more compliant, they make the bike and rider rise and
fall through shorter displacements and more gradually, reducing
hysteresis losses in the rider.

How much less does a wide tire deflect?
The contact patch is larger,
so the perimeter of the contact patch is longer,
so the area of greatest curvature is larger.

A wider tire has a flatter angle of incidence at the contact patch,
hence less strain in the tread and casing there. *Deflecting a large
casing at e.g. a 20 degree angle from the tangent, as in a balloon
tire, takes less work than deflecting a narrow casing at e.g. a 90
degree angle from the tangent, as in a narrow racing tire supporting
the same load (given directly comparable construction).

Why? *Hysteresis loss in rubber is characterized as proportional to
the square of the strain. *The perimeter length of the contact patch
is proportional to the _square root_ of the contact patch's area.
Make a tire narrower, and its rubber strain at the contact patch
increases disproportionately, while the perimeter length of its
contact patch changes by only a relatively small amount.

If the tires are of identical tread and similar casing strength _with
respect to their properly inflated casing hoop stress_, then the one
that contacts the ground more tangentially will have less internal
loss under load, at the same load.

It's not the nature of wide tires to have higher internal losses.
Rather it's the nature of the market for wide tires to favor
durability and puncture resistance, and these tend to add rolling
resistance.

Chalo

Bravo;

Best-written post (in English) on the topic in years.

Harry Travis

I liked it.
TJ

In article
,
Chalo wrote:

Michael Press wrote:

*Chalo wrote:

Michael Press wrote:

As the tire gets wider the physics of pressure vessels demands
that the tire casing be stronger in tension. This means that
wider tires must be made with thicker, less flexible, more
power consuming casings than thinner tires.

And they distort less at the contact patch. *And when they are lower
in pressure and more compliant, they make the bike and rider rise and
fall through shorter displacements and more gradually, reducing
hysteresis losses in the rider.

How much less does a wide tire deflect?
The contact patch is larger,
so the perimeter of the contact patch is longer,
so the area of greatest curvature is larger.

A wider tire has a flatter angle of incidence at the contact patch,
hence less strain in the tread and casing there. Deflecting a large
casing at e.g. a 20 degree angle from the tangent, as in a balloon
tire, takes less work than deflecting a narrow casing at e.g. a 90
degree angle from the tangent, as in a narrow racing tire supporting
the same load (given directly comparable construction).

Why? Hysteresis loss in rubber is characterized as proportional to
the square of the strain. The perimeter length of the contact patch
is proportional to the _square root_ of the contact patch's area.
Make a tire narrower, and its rubber strain at the contact patch
increases disproportionately, while the perimeter length of its
contact patch changes by only a relatively small amount.

If the tires are of identical tread and similar casing strength _with
respect to their properly inflated casing hoop stress_, then the one
that contacts the ground more tangentially will have less internal
loss under load, at the same load.

Not all the flex is at the contact patch. Tires flex in the
sidewall. Wide tires are bigger and more material flexes.
We have a number of interconnected phenomena acting in
different ways.

It's not the nature of wide tires to have higher internal losses.
Rather it's the nature of the market for wide tires to favor
durability and puncture resistance, and these tend to add rolling
resistance.

Then fast tires should be made wide. They could dispense
with the heavy tread, use thin casings and reap all the
benefits of wide tires.

--
Michael Press

On Mar 12, 8:56*pm, Michael Press wrote:
Then fast tires should be made wide. They could dispense
with the heavy tread, use thin casings and reap all the
benefits of wide tires.

They are. You just to know what you are looking for. Schwalbe makes
the Marathon Supreme (690 grams) up to 50-622 in folding. Granted,
they are not Ultremo 'R' HS 380's, but they are at least comparable to
narrower versions of the same tyre in 32-622, 37-622, and 42-622
sizes. They make the Big Apple in folding versions too, but the size
range is more limited.

Chris

On 13 Mar 2009 08:41:46 GMT, wrote:

Too bad the good old days of 180g tubular tires are gone or you would
have seen that the fastest track tires were 120TPI (0.2mm silk thread)
in each of the two plies and had latex rubber as inter-ply bonding
with a 1mm thick smooth latex tread glued to the 25mm diameter casing
of bare white silk (seta) side walls (0.4mm thick) with latex. Their
base tape was thin without rubber coating and was glued to the rim
with shellac.

These tires were ridden on tracks with 130-170psi inflation pressure
[some material snipped]
The ancients knew where the losses were and knew how to beat them.
There are no such tires today.

Yeah, no such tires today. Not silk. Five grams heavier:
http://www.conti-online.com/generato...lympic_en.html

John Forrest Tomlinson wrote:
On 13 Mar 2009 08:41:46 GMT, wrote:
[...]
The ancients knew where the losses were and knew how to beat them.
There are no such tires today.

Yeah, no such tires today. Not silk. Five grams heavier:
http://www.conti-online.com/generato...lympic_en.html

"Our ASC silica compound provides reliable grip on wood and cement tracks."

WTH is s "cement" track?

--
Tom Sherman - 42.435731,-83.985007
LOCAL CACTUS EATS CYCLIST - datakoll