| |
Main
Date: 29 May 2007 13:50:30
From: bfd
Subject: faster casing = faster tires?!@
|
According to Jan Heine, Vintage Bicycle Quarterly (VBQ) publisher and
French Constructeur AND 650B advocate, his testing found:
"that slow casings make tires slow, and fast casings make tires fast.
This is much more important than diameter or width.
Yes, wider tires are faster, but...
- many wide tires use slow casings. If they were narrower, they'd be
even slower!
- any narrow racing tires use fast casings, so they are faster than
the wide tires. If they were wider, they would be even faster!
The Grand Bois tires have shown that you can make wide tires with fast
casings. It's just that few people have known how (or have bothered to
do it) until recently."
It should also be noted that the now discontinued 584x38 Misuboshi
Trimline, the choice tire of 650B advocates, was also suppose to be
build around *fast* casings. In contrast, the often criticized, but
available 684x38 Panaracer Col de Vie is build around "slow" casing
and rides like it.
I ride on Avocet Road 700x25 tires pumped up to around 85-90psi. They
feel *fast* and are very comfortable. So, the question is how do you
tell whether a tire is build around *fast* casing or "slow" casing?
Or, is this just a myth?
|
|
| |
Date: 01 Jun 2007 13:05:55
From: Jeff L
Subject: Re: faster casing = faster tires?!@
|
On Jun 1, 12:14 pm, jobst.bra...@stanfordalumni.org wrote:
<snipped > > I have several questions about tires and rolling
resistance.
> > A clincher has been proven to have a lower rolling resistance than a
> > tubular because of hysteresis. From what I can tell though all the
> > tests have been done with road tubular glue. The difference seems
> > to be about 5-10 watts. How much will track glue lower the
> > difference?
>
> Who has proven this and what was the basis of comparison?
I was quoting the study done at the Continental factory in Germany by
some magazine in, I believe, 2005. I know I have the losses listed
correctly as 5-10 w even though I can't find the link (it's on my home
computer but I'm sure you are aware of the study). I think maybe my
error was not in the #s quoted, but in labelling the cause as
hystersis. I thought that was the term for the losses from the tire
moving on the rim because of the elasticity of the glue.
> in road glue (sticky self adhesive) is where tubulars generate losses.
> For this reason track tires are glued on with hard glue and have bare
> cloth base tape. Such tires have lower RR than any clincher that I
> have seen.
That was my question. I understand that is true when using road glue
but is it true when using true track glues?. The chart at
http://www.analyticcycling.com/ForcesTires_Page.html
shows the lower resistance as being a "high quaility" tubular with
track glue (the bottom blue line).
>
> http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html
>
> > Higher inflation pressures mean a lower rolling resistance but, as I
> > understand it, that is for smooth surfaces like wood tracks, steel
> > drums etc. In real life out on the road the transfer of energy
> > means lower pressures outperform high pressures. Am I correct, and
> > how do you determine the correct pressure for a given situation (eg
> > one tire brand and a given surface).
>
> I think you should review what causes rolling losses. As has been
> mentioned, the two main effects are casing, tube, and tread flex, and
> tread squirm, that motion of a tread feature bulging into adjacent
> voids to the tread feature. The second is the largest loss in knobby
> tires on hard surfaces.
I think I have an ok conception of the forces but obviously didn't
label them correctly.
>
> > PS for Jobst. The graph of rolling resistance values for different
> > tires in your 2004 article hosted on Sheldon Brown doesn't give a
> > good description of the various tires. Is there a link somewhere to
> > the brands so that we can tell where the tubulars ranked?.
>
> It doesn't matter. These tires are mostly out of production but the
> comparative values are as valid as they were then. The tests were
> done by IRC on typical steel drum rolling tests, all with the same
> inflation pressure and all clinchers with the same inner tubes. You
> can draw your own conclusions after understanding what was measured.
I understand the tires are all out of production but in the list it is
impossible to tell which of the 2 lines are for the clinchers and
which ones are the tubulars. IF the tubulars are two of the lines
closer to the top of the chart then how come the AC chart I just
linked to showed the tubular being lower? That's what I don't
understand.
Thanks
>
> Since we are not interested in worst case conditions when selecting a
> road tire, a smooth drum measures that which is most important to a
> slick tread tire for the road. The tires that do not have the same
> characteristic curve as most are ones with patterned read with tread
> squirm. A slick does not have that because rubber is incompressible,
> it cannot squirm from contact pressure as, for instance, a tread knob.
>
> Any losses on a smooth drum only get uniformly worse for all tires, on
> rougher surfaces. I think you can derive that if you think about what
> causes rolling losses
>
> Jobst Brandt- Hide quoted text -
>
> - Show quoted text -
|
| | |
Date: 01 Jun 2007 21:33:04
From:
Subject: Re: faster casing = faster tires?!@
|
Jeff L Watts writes:
>>>> I have several questions about tires and rolling resistance.
>>> A clincher has been proven to have a lower rolling resistance than
>>> a tubular because of hysteresis. From what I can tell though all
>>> the tests have been done with road tubular glue. The difference
>>> seems to be about 5-10 watts. How much will track glue lower the
>>> difference?
>> Who has proven this and what was the basis of comparison?
> I was quoting the study done at the Continental factory in Germany
> by some magazine in, I believe, 2005. I know I have the losses
> listed correctly as 5-10 w even though I can't find the link (it's
> on my home computer but I'm sure you are aware of the study). I
> think maybe my error was not in the #s quoted, but in labeling the
> cause as hysteresis. I thought that was the term for the losses from
> the tire moving on the rim because of the elasticity of the glue.
That doesn't hold much water if they didn't say how that came to pass.
Tubular racing tires are essentially bare-wall and have no rubber on
the inside. Because the losses in tires are from elastomeric
hysteresis and tubulars have far less of inter-ply binders, and those
they have are latex rubber, the least lossy of rubber compounds, this
does not make sense. However, as I mentioned, rim glue is the culprit
and the ancients knew this. That is why tack tires are glues on with
hard glue.
I think they swept rim glue under the carpet and called tubulars more
lossy without explaining where they got that.
>> in road glue (sticky self adhesive) is where tubulars generate
>> losses. For this reason track tires are glued on with hard glue
>> and have bare cloth base tape. Such tires have lower RR than any
>> clincher that I have seen.
> That was my question. I understand that is true when using road glue
> but is it true when using true track glues?. The chart at
http://www.analyticcycling.com/ForcesTires_Page.html
> shows the lower resistance as being a "high quality" tubular with
> track glue (the bottom blue line).
That's up to you as to what glue you use. There are some pressure
sensitive glues that are not readily useful for mounting a spare if
the installed tire goes flat. Some of these have practically no
effect on RR, certainly better than a similar sized clincher.
http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html
>>> Higher inflation pressures mean a lower rolling resistance but, as
>>> I understand it, that is for smooth surfaces like wood tracks,
>>> steel drums etc. In real life out on the road the transfer of
>>> energy means lower pressures outperform high pressures. Am I
>>> correct, and how do you determine the correct pressure for a given
>>> situation (eg one tire brand and a given surface).
>> I think you should review what causes rolling losses. As has been
>> mentioned, the two main effects are casing, tube, and tread flex,
>> and tread squirm, that motion of a tread feature bulging into
>> adjacent voids to the tread feature. The second is the largest
>> loss in knobby tires on hard surfaces.
> I think I have an OK conception of the forces but obviously didn't
> label them correctly.
>>> PS for Jobst. The graph of rolling resistance values for
>>> different tires in your 2004 article hosted on Sheldon Brown
>>> doesn't give a good description of the various tires. Is there a
>>> link somewhere to the brands so that we can tell where the
>>> tubulars ranked?.
>> It doesn't matter. These tires are mostly out of production but
>> the comparative values are as valid as they were then. The tests
>> were done by IRC on typical steel drum rolling tests, all with the
>> same inflation pressure and all clinchers with the same inner
>> tubes. You can draw your own conclusions after understanding what
>> was measured.
> I understand the tires are all out of production but in the list it
> is impossible to tell which of the 2 lines are for the clinchers and
> which ones are the tubulars. IF the tubulars are two of the lines
> closer to the top of the chart then how come the AC chart I just
> linked to showed the tubular being lower? That's what I don't
> understand.
On the above graph, each tire and its symbol is listed. The tubulars
are the fat black and blue lines that do not conform to the trend,
mainly because they have a constant offset upward, caused by glue
losses. If you look carefully, you can see how large that loss is by
visually placing the two curves at the bottom of the graph, these
being a family of identical curves with a multiplier. The differences
in one or two of these is their tread squirm that is not proportional
to inflation pressure.
It was when I saw these curves, that the reason for track
glue became obvious, no one having that answer for me over the years
of observing the hard glue ritual that was practiced like tying and
soldering spokes, with no understanding of what and why.
> Thanks
>> Since we are not interested in worst case conditions when selecting
>> a road tire, a smooth drum measures that which is most important to
>> a slick tread tire for the road. The tires that do not have the
>> same characteristic curve as most are ones with patterned read with
>> tread squirm. A slick does not have that because rubber is
>> incompressible, it cannot squirm from contact pressure as, for
>> instance, a tread knob.
>> Any losses on a smooth drum only get uniformly worse for all tires,
>> on rougher surfaces. I think you can derive that if you think
>> about what causes rolling losses
Jobst Brandt
|
| |
Date: 31 May 2007 18:58:42
From:
Subject: Re: faster casing = faster tires?!@
|
On May 30, 5:29 pm, jobst.bra...@stanfordalumni.org wrote:
> Tim McNamara writes:
> >> To follow up on some of Tim's comments (though not related to the
> >> casing issue), I'm pretty sure a tires rolling resistance drops as
> >> the tread wears off.
> > That would make sense. Heine also thought there is a "break-in"
> > period in which the casing "loosens up," but I have never seen that
> > mentioned anywhere else.
>
> You'll need to explain what you mean by "loosen up". If you mean
> delamination, that doesn't lower internal losses in a tire because it
> adds sliding friction to elastomeric losses. Rolling resistance of
> tires in good condition is almost entirely hysteretic losses in
> elastomers, tread, tube, sidewall rubber and inter-ply binders.
>
> I have not seen a tire develop separated cords even when worn through
> the tread exposing these cords.
>
> Jobst Brandt
I have several questions about tires and rolling resistance.
A clincher has been proven to have a lower rolling resistance than a
tubular because of hystersis. From what I can tell though all the
tests have been done with road tubular glue. The difference seems to
be about 5-10 watts. How much will track glue lower the difference?
Higher inflation pressures mean a lower rolling resistance but, as I
understand it, that is for smooth surfaces like wood tracks, steel
drums etc. In real life out on the road the transfer of energy means
lower pressures outperform high pressures. Am I correct, and how do
you determine the correct pressure for a given situation (eg one tire
brand and a given surface).
Thanks
PS for Jobst. The graph of rolling resistance values for different
tires in your 2004 article hosted on Sheldon Brown doesn't give a good
description of the various tires. Is there a link somewhere to the
brands so that we can tell where the tubulars ranked?.
|
| | |
Date: 01 Jun 2007 16:14:02
From:
Subject: Re: faster casing = faster tires?!@
|
someone writes:
>>>> To follow up on some of Tim's comments (though not related to the
>>>> casing issue), I'm pretty sure a tires rolling resistance drops
>>>> as the tread wears off.
>>> That would make sense. Heine also thought there is a "break-in"
>>> period in which the casing "loosens up," but I have never seen
>>> that mentioned anywhere else.
>> You'll need to explain what you mean by "loosen up". If you mean
>> delamination, that doesn't lower internal losses in a tire because
>> it adds sliding friction to elastomeric losses. Rolling resistance
>> of tires in good condition is almost entirely hysteretic losses in
>> elastomers, tread, tube, sidewall rubber and inter-ply binders.
>> I have not seen a tire develop separated cords even when worn
>> through the tread exposing these cords.
> I have several questions about tires and rolling resistance.
> A clincher has been proven to have a lower rolling resistance than a
> tubular because of hysteresis. From what I can tell though all the
> tests have been done with road tubular glue. The difference seems
> to be about 5-10 watts. How much will track glue lower the
> difference?
Who has proven this and what was the basis of comparison? The losses
in road glue (sticky self adhesive) is where tubulars generate losses.
For this reason track tires are glued on with hard glue and have bare
cloth base tape. Such tires have lower RR than any clincher that I
have seen.
http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html
> Higher inflation pressures mean a lower rolling resistance but, as I
> understand it, that is for smooth surfaces like wood tracks, steel
> drums etc. In real life out on the road the transfer of energy
> means lower pressures outperform high pressures. Am I correct, and
> how do you determine the correct pressure for a given situation (eg
> one tire brand and a given surface).
I think you should review what causes rolling losses. As has been
mentioned, the two main effects are casing, tube, and tread flex, and
tread squirm, that motion of a tread feature bulging into adjacent
voids to the tread feature. The second is the largest loss in knobby
tires on hard surfaces.
> PS for Jobst. The graph of rolling resistance values for different
> tires in your 2004 article hosted on Sheldon Brown doesn't give a
> good description of the various tires. Is there a link somewhere to
> the brands so that we can tell where the tubulars ranked?.
It doesn't matter. These tires are mostly out of production but the
comparative values are as valid as they were then. The tests were
done by IRC on typical steel drum rolling tests, all with the same
inflation pressure and all clinchers with the same inner tubes. You
can draw your own conclusions after understanding what was measured.
Since we are not interested in worst case conditions when selecting a
road tire, a smooth drum measures that which is most important to a
slick tread tire for the road. The tires that do not have the same
characteristic curve as most are ones with patterned read with tread
squirm. A slick does not have that because rubber is incompressible,
it cannot squirm from contact pressure as, for instance, a tread knob.
Any losses on a smooth drum only get uniformly worse for all tires, on
rougher surfaces. I think you can derive that if you think about what
causes rolling losses.
Jobst Brandt
|
| | |
Date: 01 Jun 2007 09:34:41
From: Tim McNamara
Subject: Re: faster casing = faster tires?!@
|
In article <1180663122.217899.51130@k79g2000hse.googlegroups.com >,
WattsUpDok@gmail.com wrote:
> On May 30, 5:29 pm, jobst.bra...@stanfordalumni.org wrote:
> > Tim McNamara writes:
> > >> To follow up on some of Tim's comments (though not related to
> > >> the casing issue), I'm pretty sure a tires rolling resistance
> > >> drops as the tread wears off.
> > > That would make sense. Heine also thought there is a "break-in"
> > > period in which the casing "loosens up," but I have never seen
> > > that mentioned anywhere else.
> >
> > You'll need to explain what you mean by "loosen up". If you mean
> > delamination, that doesn't lower internal losses in a tire because
> > it adds sliding friction to elastomeric losses. Rolling resistance
> > of tires in good condition is almost entirely hysteretic losses in
> > elastomers, tread, tube, sidewall rubber and inter-ply binders.
> >
> > I have not seen a tire develop separated cords even when worn
> > through the tread exposing these cords.
> >
> > Jobst Brandt
>
> I have several questions about tires and rolling resistance.
>
> A clincher has been proven to have a lower rolling resistance than a
> tubular because of hystersis. From what I can tell though all the
> tests have been done with road tubular glue. The difference seems to
> be about 5-10 watts. How much will track glue lower the difference?
You can see the curves here:
http://bike.terrymorse.com/rolres.html
and some discussion that might answer some of your questions including
the losses due to tubulars squirming on the glue, here:
http://bike.terrymorse.com/rrdiscuss.html
> Higher inflation pressures mean a lower rolling resistance but, as I
> understand it, that is for smooth surfaces like wood tracks, steel
> drums etc. In real life out on the road the transfer of energy means
> lower pressures outperform high pressures. Am I correct, and how do
> you determine the correct pressure for a given situation (eg one tire
> brand and a given surface).
There has been an argument to this effect, which I first read here in
r.b.t. at least a decade ago by Jim Papadopolous. His contention was
that at as inflation pressure goes up, the tire begins to bounce over
surface irregularities rather than absorbing them and that this slows
down the rider. We've all ridden over new roads with smooth asphalt and
old roads with rough asphalt and noticed that it takes a bit more effort
to ride over the latter.
More recently this issue was taken up by Jan Heine and published in
Bicycle Quarterly. The outcome of that testing generated much
controversy, which can be read in the Google archives of the newsgroup
if you missed it at the time.
I suppose that rolling resistance tests on a steel drum can never
perfectly model rolling on the road. However I would expect that the
ordinal ranking would be similar even if the absolute measurement of
rolling resistance would be different. And there are other issues that
are important, such as puncture resistance, tread durability, ease of
installation and removal, etc.
> PS for Jobst. The graph of rolling resistance values for different
> tires in your 2004 article hosted on Sheldon Brown doesn't give a
> good description of the various tires. Is there a link somewhere to
> the brands so that we can tell where the tubulars ranked?.
You can see where the tubulars ranked just by looking at the curves. As
far as the various tires go, I don't think any of them are still in
production any more. Those that are still in production under the same
names have been changed in various ways.
|
| |
Date: 30 May 2007 10:48:22
From: Matt O'Toole
Subject: Re: faster casing = faster tires?!@
|
On Tue, 29 May 2007 13:50:30 -0700, bfd wrote:
> So, the question is how do you
> tell whether a tire is build around *fast* casing or "slow" casing?
> Or, is this just a myth?
Put it on a test rig and test it for rolling resistance.
Matt O.
|
| | |
Date: 30 May 2007 20:23:01
From:
Subject: Re: faster casing = faster tires?!@
|
Matt O'Toole writes:
>> So, the question is how do you tell whether a tire is build around
>> *fast* casing or "slow" casing? Or, is this just a myth?
> Put it on a test rig and test it for rolling resistance.
Well, what do you call a "fast casing"? The classic definition of low
RR tires has often been based on (actual) TPI (threads per inch) of
the casing. TPI tells approximately thickness of a casing ply of which
a bicycle tire has two. This can be determined by actual count or by
measuring the thickness of the sidewall for comparison with a tire of
known low RR.
Wall thickness is a measure of how much elastomer surrounds casing
fibers and resultant casing bending stiffness, that being the cause of
flexural losses in a tire. Beyond that, tread thickness plays a major
role. Generally tires with high TPI have relatively thinner treads,
not wanting to throw away in tread losses what was gained in a more
expensive casing. Kevlar and other anti puncture plies generally
place tires in the high RR category so they need not be considered in
this respect.
The thump-with-the-finger ring test isn't bad, because it measures
damping (losses) in the tire at a given inflation pressure. This is a
good comparison. In the days of yore, it was a pleasure to thump Tipo
00 Clement track tires and listen to them ring
Jobst Brandt
|
| |
Date: 29 May 2007 15:50:27
From: bfd
Subject: Re: faster casing = faster tires?!@
|
On May 29, 3:42 pm, Chalo <chalo.col...@gmail.com > wrote:
> bfd wrote:
>
> > So, the question is how do you
> > tell whether a tire is build around *fast* casing or "slow" casing?
> > Or, is this just a myth?
>
> The "speed" of a tire is a function of the tire's ability to
> elastically restore the mechanical energy stored in the process of
> distorting it. Any energy that is dissipated into the tire's casing
> or tread as heat can't be returned to sustain the forward motion of
> the bike.
>
> In the same way as a normal rubber band gets warm if it's repeatedly
> stretched and released, the rubber and other resins in a tire sink
> energy when they are worked. Tread and casing thickness is usually
> singled out as the main culprit in hysteresis loss, but casing
> construction that causes a large amount of shearing action between its
> layers (as all bias-ply tires do to some extent) can be lossier than
> its physical thickness would otherwise indicate. Radial tires for
> bicycles (which should by their nature display much less hysteresis
> loss than bias-ply) have been brought to market, but their handling
> qualities and subjective feel have made them unpopular and
> unsuccessful in the marketplace.
>
> The wider or larger in diameter a tire is, the less its tread and
> casing are distorted under a given load and pressure, and the less its
> hysteresis losses will be (all else equal).
>
> The other form of kinetic energy loss that is inseparable from other
> tire losses is the tendency of a hard tire to transmit energy as jolts
> to the rider's body. This latter type of loss can easily make a
> "fast", low hysteresis tire draggier overall than a "slow", softer
> tire. Larger wheels and wider tires help in ths regard as well.
>
> Avocet Fas-Grip tires seem to have all the right stuff from an
> efficiency standpoint-- relatively thin, smooth treads with tapered
> edges; thin, high thread count casings; time-proven lampblack tread
> rubber; and modestly wide sizes available. I have yet to find a tire
> that feels more efficient in any given size than Avocet slicks. My
> favorite has been the 26 x 1.9" size, which unfortunately is no longer
> manufactured.
>
That's interesting, Avocet still list a Fasgrip City and Fasgrip City
K in 26x1.9, both with 66 tpi too!
http://avocet.com/tirepages/carbon12_specs.html
The main problem with Avocet has always been their screwed up,
antiquated distribution system (or lack thereof). Supposedly, any LBS
should be able to order tires directly from Avocet. Good Luck with
that!
|
| | |
Date: 30 May 2007 11:00:54
From: Matt O'Toole
Subject: Re: faster casing = faster tires?!@
|
On Tue, 29 May 2007 15:50:27 -0700, bfd wrote:
> On May 29, 3:42 pm, Chalo <chalo.col...@gmail.com> wrote:
>> bfd wrote:
>>
>> > So, the question is how do you
>> > tell whether a tire is build around *fast* casing or "slow" casing?
>> > Or, is this just a myth?
>>
>> The "speed" of a tire is a function of the tire's ability to
>> elastically restore the mechanical energy stored in the process of
>> distorting it. Any energy that is dissipated into the tire's casing
>> or tread as heat can't be returned to sustain the forward motion of
>> the bike.
>>
>> In the same way as a normal rubber band gets warm if it's repeatedly
>> stretched and released, the rubber and other resins in a tire sink
>> energy when they are worked. Tread and casing thickness is usually
>> singled out as the main culprit in hysteresis loss, but casing
>> construction that causes a large amount of shearing action between its
>> layers (as all bias-ply tires do to some extent) can be lossier than
>> its physical thickness would otherwise indicate. Radial tires for
>> bicycles (which should by their nature display much less hysteresis
>> loss than bias-ply) have been brought to market, but their handling
>> qualities and subjective feel have made them unpopular and
>> unsuccessful in the marketplace.
>>
>> The wider or larger in diameter a tire is, the less its tread and
>> casing are distorted under a given load and pressure, and the less its
>> hysteresis losses will be (all else equal).
>>
>> The other form of kinetic energy loss that is inseparable from other
>> tire losses is the tendency of a hard tire to transmit energy as jolts
>> to the rider's body. This latter type of loss can easily make a
>> "fast", low hysteresis tire draggier overall than a "slow", softer
>> tire. Larger wheels and wider tires help in ths regard as well.
>>
>> Avocet Fas-Grip tires seem to have all the right stuff from an
>> efficiency standpoint-- relatively thin, smooth treads with tapered
>> edges; thin, high thread count casings; time-proven lampblack tread
>> rubber; and modestly wide sizes available. I have yet to find a tire
>> that feels more efficient in any given size than Avocet slicks. My
>> favorite has been the 26 x 1.9" size, which unfortunately is no longer
>> manufactured.
>>
> That's interesting, Avocet still list a Fasgrip City and Fasgrip City
> K in 26x1.9, both with 66 tpi too!
>
> http://avocet.com/tirepages/carbon12_specs.html
>
> The main problem with Avocet has always been their screwed up,
> antiquated distribution system (or lack thereof). Supposedly, any LBS
> should be able to order tires directly from Avocet. Good Luck with
> that!
Why bother when you can get Performance/Nashbar slicks that are 95% as
good, for $9.99, and get 'em in a couple of days -- instead of waiting
weeks for the privilege of paying $30/tire.
Matt O.
|
| | |
Date: 29 May 2007 20:45:40
From: Tim McNamara
Subject: Re: faster casing = faster tires?!@
|
In article <1180479027.562380.12220@g4g2000hsf.googlegroups.com >,
bfd <bfd853@yahoo.com > wrote:
> The main problem with Avocet has always been their screwed up,
> antiquated distribution system (or lack thereof). Supposedly, any LBS
> should be able to order tires directly from Avocet. Good Luck with
> that!
In the past there has been a high minimum order- too high- that had
discouraged bike shops from buying their tires. I don't know if that is
still the case.
|
| | | |
Date: 29 May 2007 22:12:34
From: A Muzi
Subject: Re: faster casing = faster tires?!@
|
> In article <1180479027.562380.12220@g4g2000hsf.googlegroups.com>,
> bfd <bfd853@yahoo.com> wrote:
>> The main problem with Avocet has always been their screwed up,
>> antiquated distribution system (or lack thereof). Supposedly, any LBS
>> should be able to order tires directly from Avocet. Good Luck with
>> that!
Tim McNamara wrote:
> In the past there has been a high minimum order- too high- that had
> discouraged bike shops from buying their tires. I don't know if that is
> still the case.
I don't recall that as an issue. It may well be.
Our tire vendors ship to arrive the next morning on 4pm orders. Avocet
is not at all convenient in that regard.
Our tire vendors ship tires mixed with daily shipments of other goods -
from Tourney changers to frames to Record Ergos - which are shipping
anyway.
There are other business level factors. With today's huge inventory
levels over relatively static volume I can no longer justify the
commitment. YMMV.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
|
| |
Date: 29 May 2007 15:42:08
From: Chalo
Subject: Re: faster casing = faster tires?!@
|
bfd wrote:
>
> So, the question is how do you
> tell whether a tire is build around *fast* casing or "slow" casing?
> Or, is this just a myth?
The "speed" of a tire is a function of the tire's ability to
elastically restore the mechanical energy stored in the process of
distorting it. Any energy that is dissipated into the tire's casing
or tread as heat can't be returned to sustain the forward motion of
the bike.
In the same way as a normal rubber band gets warm if it's repeatedly
stretched and released, the rubber and other resins in a tire sink
energy when they are worked. Tread and casing thickness is usually
singled out as the main culprit in hysteresis loss, but casing
construction that causes a large amount of shearing action between its
layers (as all bias-ply tires do to some extent) can be lossier than
its physical thickness would otherwise indicate. Radial tires for
bicycles (which should by their nature display much less hysteresis
loss than bias-ply) have been brought to market, but their handling
qualities and subjective feel have made them unpopular and
unsuccessful in the marketplace.
The wider or larger in diameter a tire is, the less its tread and
casing are distorted under a given load and pressure, and the less its
hysteresis losses will be (all else equal).
The other form of kinetic energy loss that is inseparable from other
tire losses is the tendency of a hard tire to transmit energy as jolts
to the rider's body. This latter type of loss can easily make a
"fast", low hysteresis tire draggier overall than a "slow", softer
tire. Larger wheels and wider tires help in ths regard as well.
Avocet Fas-Grip tires seem to have all the right stuff from an
efficiency standpoint-- relatively thin, smooth treads with tapered
edges; thin, high thread count casings; time-proven lampblack tread
rubber; and modestly wide sizes available. I have yet to find a tire
that feels more efficient in any given size than Avocet slicks. My
favorite has been the 26 x 1.9" size, which unfortunately is no longer
manufactured.
Chalo
|
| |
Date: 29 May 2007 15:17:46
From: bfd
Subject: Re: faster casing = faster tires?!@
|
On May 29, 3:12 pm, Tim McNamara <tim...@bitstream.net > wrote:
> In article <1180471830.566154.158...@h2g2000hsg.googlegroups.com>,
>
>
>
>
>
> bfd <bfd...@yahoo.com> wrote:
> > According to Jan Heine, Vintage Bicycle Quarterly (VBQ) publisher and
> > French Constructeur AND 650B advocate, his testing found:
>
> > "that slow casings make tires slow, and fast casings make tires fast.
> > This is much more important than diameter or width.
>
> > Yes, wider tires are faster, but...
>
> > - many wide tires use slow casings. If they were narrower, they'd be
> > even slower!
>
> > - any narrow racing tires use fast casings, so they are faster than
> > the wide tires. If they were wider, they would be even faster!
>
> > The Grand Bois tires have shown that you can make wide tires with
> > fast casings. It's just that few people have known how (or have
> > bothered to do it) until recently."
>
> > It should also be noted that the now discontinued 584x38 Misuboshi
> > Trimline, the choice tire of 650B advocates, was also suppose to be
> > build around *fast* casings. In contrast, the often criticized, but
> > available 684x38 Panaracer Col de Vie is build around "slow" casing
> > and rides like it.
>
> > I ride on Avocet Road 700x25 tires pumped up to around 85-90psi. They
> > feel *fast* and are very comfortable. So, the question is how do you
> > tell whether a tire is build around *fast* casing or "slow" casing?
> > Or, is this just a myth?
>
> Well, Jan's article raised a lot of discussion, mainly about the quality
> of the data, but there were some things that I think are well-agreed
> upon. First is that rolling resistance is due to hysteresis - the
> energy lost in the flexing of the tire as it rolls through the contact
> patch. The less energy this flexing absorbs, the lower the rolling
> resistance.
>
> All other things being equal, more supple casing and more flexible
> rubber are two ways to lower rolling resistance. Using finer gauge
> threads in the casing (127 threads per inch versus 66, for example)
> should result in a more supple casing with less rolling resistance. A
> thinner rubber tread and thinner rubber on the sidewalls results in less
> energy being absorbed in flexing. Different rubber compounds can also
> affect this, such as rubber with carbon black or silica. The inner tube
> is also an issue. Tread patterns also increase rolling resistance.
>
> Think about the days of high performance silk tubulars such as the
> Criterium Seta- a very thin latex tube, a very thin and supple casing,
> and a very thin rubber tread with a slight decorative pattern that wore
> off in a few miles.
>
> Basically at this time, the consumer is presented with a choice between
> skinny high performance tires with supple casings and thin treads, or
> wider "utility" tires with thick casings and thick rubber treads for
> puncture resistance. If you can find the Schwalbe display in a bike
> shop with sections of about 12 different tire models, you can see this
> quite clearly. Jan wants wide tires with thin supple casings and thin
> rubber treads.
>
> There's a "break point" at which the tire is too wide to use a thin
> casing made with fine gauge thread due to casing tension. IIRC that is
> about 25-28 mm. Tires wider than that need a heavier casing such as a
> 66 tpi fabric.
>
> So there's more than just casing affecting the rolling resistance of
> tires.- Hide quoted text -
>
Thanks. I wonder how much fabric, i.e., tpi, the *fast* Gran Bois or
discontinued Mitsuboshi Trimline have in them?
|
| | |
Date: 29 May 2007 20:49:06
From: Tim McNamara
Subject: Re: faster casing = faster tires?!@
|
In article <1180477066.688161.179460@m36g2000hse.googlegroups.com >,
bfd <bfd853@yahoo.com > wrote:
> I wonder how much fabric, i.e., tpi, the *fast* Gran Bois or
> discontinued Mitsuboshi Trimline have in them?
No idea.
|
| |
Date: 29 May 2007 17:12:15
From: Tim McNamara
Subject: Re: faster casing = faster tires?!@
|
In article <1180471830.566154.158900@h2g2000hsg.googlegroups.com >,
bfd <bfd853@yahoo.com > wrote:
> According to Jan Heine, Vintage Bicycle Quarterly (VBQ) publisher and
> French Constructeur AND 650B advocate, his testing found:
>
> "that slow casings make tires slow, and fast casings make tires fast.
> This is much more important than diameter or width.
>
> Yes, wider tires are faster, but...
>
> - many wide tires use slow casings. If they were narrower, they'd be
> even slower!
>
> - any narrow racing tires use fast casings, so they are faster than
> the wide tires. If they were wider, they would be even faster!
>
> The Grand Bois tires have shown that you can make wide tires with
> fast casings. It's just that few people have known how (or have
> bothered to do it) until recently."
>
> It should also be noted that the now discontinued 584x38 Misuboshi
> Trimline, the choice tire of 650B advocates, was also suppose to be
> build around *fast* casings. In contrast, the often criticized, but
> available 684x38 Panaracer Col de Vie is build around "slow" casing
> and rides like it.
>
>
> I ride on Avocet Road 700x25 tires pumped up to around 85-90psi. They
> feel *fast* and are very comfortable. So, the question is how do you
> tell whether a tire is build around *fast* casing or "slow" casing?
> Or, is this just a myth?
Well, Jan's article raised a lot of discussion, mainly about the quality
of the data, but there were some things that I think are well-agreed
upon. First is that rolling resistance is due to hysteresis - the
energy lost in the flexing of the tire as it rolls through the contact
patch. The less energy this flexing absorbs, the lower the rolling
resistance.
All other things being equal, more supple casing and more flexible
rubber are two ways to lower rolling resistance. Using finer gauge
threads in the casing (127 threads per inch versus 66, for example)
should result in a more supple casing with less rolling resistance. A
thinner rubber tread and thinner rubber on the sidewalls results in less
energy being absorbed in flexing. Different rubber compounds can also
affect this, such as rubber with carbon black or silica. The inner tube
is also an issue. Tread patterns also increase rolling resistance.
Think about the days of high performance silk tubulars such as the
Criterium Seta- a very thin latex tube, a very thin and supple casing,
and a very thin rubber tread with a slight decorative pattern that wore
off in a few miles.
Basically at this time, the consumer is presented with a choice between
skinny high performance tires with supple casings and thin treads, or
wider "utility" tires with thick casings and thick rubber treads for
puncture resistance. If you can find the Schwalbe display in a bike
shop with sections of about 12 different tire models, you can see this
quite clearly. Jan wants wide tires with thin supple casings and thin
rubber treads.
There's a "break point" at which the tire is too wide to use a thin
casing made with fine gauge thread due to casing tension. IIRC that is
about 25-28 mm. Tires wider than that need a heavier casing such as a
66 tpi fabric.
So there's more than just casing affecting the rolling resistance of
tires.
|
| | |
Date: 30 May 2007 10:56:02
From: Matt O'Toole
Subject: Re: faster casing = faster tires?!@
|
On Tue, 29 May 2007 17:12:15 -0500, Tim McNamara wrote:
> There's a "break point" at which the tire is too wide to use a thin
> casing made with fine gauge thread due to casing tension. IIRC that is
> about 25-28 mm. Tires wider than that need a heavier casing such as a
> 66 tpi fabric.
There may be a technical limitation, but I suspect the "break
point" is determined by the market. Most people who want
fast tires want 23mm ones, whether they should or not. Riders or product
managers who want >25mm tires want durable, cheaper ones.
Also, sizes are only nominal. A 28mm Conti is narrower than a 25mm
Michelin.
Matt O.
|
| | | |
Date: 30 May 2007 15:57:33
From: Tim McNamara
Subject: Re: faster casing = faster tires?!@
|
In article <pan.2007.05.30.14.56.01.384057@letterboxes.org >,
Matt O'Toole <mattotoole@letterboxes.org > wrote:
> On Tue, 29 May 2007 17:12:15 -0500, Tim McNamara wrote:
>
> > There's a "break point" at which the tire is too wide to use a thin
> > casing made with fine gauge thread due to casing tension. IIRC
> > that is about 25-28 mm. Tires wider than that need a heavier
> > casing such as a 66 tpi fabric.
>
> There may be a technical limitation, but I suspect the "break point"
> is determined by the market.
From previous discussions there is an issue with casing tension- as the
casing gets larger in minor diameter, the tension on the casing at the
same inflation pressure increases significantly. At some point, it is
necessary to use a heavier casing. IIRC that point is in the 25-28 mm
range.
> Most people who want fast tires want 23mm ones, whether they should
> or not. Riders or product managers who want >25mm tires want
> durable, cheaper ones.
The latter, I think- products offered to the public are the products
that product managers and the like imagine the public wants. The idea
that the public might actually want a 28 mm wide high performance tire
tends to elude them. There is a tendency to assume 28 mm tires are used
by commuters and tourists.
> Also, sizes are only nominal. A 28mm Conti is narrower than a 25mm
> Michelin.
I've measured both at 26 mm using a calipers. Same as the Panaracer
Pasela 700 x 25. ISTR that the Avocet Road 700 x 28 measured an actual
25-26 mm (and is now marked as such).
|
| | |
Date: 29 May 2007 19:29:47
From: John Forrest Tomlinson
Subject: Re: faster casing = faster tires?!@
|
To follow up on some of Tim's comments (though not related to the
casing issue), I'm pretty sure a tires rolling resistance drops as the
tread wears off.
--
JT
****************************
Remove "remove" to reply
Visit http://www.jt10000.com
****************************
|
| | | |
Date: 29 May 2007 20:47:58
From: Tim McNamara
Subject: Re: faster casing = faster tires?!@
|
In article <4qdp53porrpln6luqr9h2n49nar1k50a28@4ax.com >,
John Forrest Tomlinson <usenetremove@jt10000.com > wrote:
> To follow up on some of Tim's comments (though not related to the
> casing issue), I'm pretty sure a tires rolling resistance drops as
> the tread wears off.
That would make sense. Heine also thought there is a "break-in" period
in which the casing "loosens up," but I have never seen that mentioned
anywhere else.
|
| | | | |
Date: 30 May 2007 21:29:06
From:
Subject: Re: faster casing = faster tires?!@
|
Tim McNamara writes:
>> To follow up on some of Tim's comments (though not related to the
>> casing issue), I'm pretty sure a tires rolling resistance drops as
>> the tread wears off.
> That would make sense. Heine also thought there is a "break-in"
> period in which the casing "loosens up," but I have never seen that
> mentioned anywhere else.
You'll need to explain what you mean by "loosen up". If you mean
delamination, that doesn't lower internal losses in a tire because it
adds sliding friction to elastomeric losses. Rolling resistance of
tires in good condition is almost entirely hysteretic losses in
elastomers, tread, tube, sidewall rubber and inter-ply binders.
I have not seen a tire develop separated cords even when worn through
the tread exposing these cords.
Jobst Brandt
|
| | | | |
Date: 30 May 2007 20:02:24
From:
Subject: Re: faster casing = faster tires?!@
|
Tim McNamara writes:
>> To follow up on some of Tim's comments (though not related to the
>> casing issue), I'm pretty sure a tires rolling resistance drops as
>> the tread wears off.
> That would make sense. Heine also thought there is a "break-in"
> period in which the casing "loosens up," but I have never seen that
> mentioned anywhere else.
You'll need to explain what you mean by "loosen up". If you mean
delamination, that doesn't lower internal losses in a tire because it
adds sliding friction to elastomeric losses. Rolling resistance of
tires in god condition is almost entirely hysteretic losses in
elastomers, tread, tube, sidewall rubber and inter-ply binders.
I have not seen a tire develop separated cords even when worn through
the tread exposing these cords.
Jobst Brandt
|
| | | | | |
Date: 30 May 2007 16:15:52
From: Tim McNamara
Subject: Re: faster casing = faster tires?!@
|
In article <465dd850$0$14123$742ec2ed@news.sonic.net >,
jobst.brandt@stanfordalumni.org wrote:
> Tim McNamara writes:
>
> >> To follow up on some of Tim's comments (though not related to the
> >> casing issue), I'm pretty sure a tires rolling resistance drops as
> >> the tread wears off.
>
> > That would make sense. Heine also thought there is a "break-in"
> > period in which the casing "loosens up," but I have never seen that
> > mentioned anywhere else.
>
> You'll need to explain what you mean by "loosen up".
He didn't define it. From context it seemed that he thought that the
casing becomes more supple over the first 200 km or so as the tire
"breaks in." I've not seen this mentioned anywhere else and I'm not
sure what mechanism Jan had in mind.
What I have seen mentioned is that when tires are first mounted and
inflated, they stretch a bit. I've measured this with calipers, pumping
my new tires up to the identified pressure in the evening and
remeasuring the next evening, finding that the tire is 1-2 mm wider and
the pressure has dropped a few psi. The latter might just be due to
osmosis, although if the casing does stretch a bit overnight then the
volume would increase and the pressure would drop a bit.
It seems to me that the casing new tires feels stiffer than used tires,
but then with used tires the tread is worn down and thinner so it's not
an apples to apples comparison.
> If you mean delamination, that doesn't lower internal losses in a
> tire because it adds sliding friction to elastomeric losses. Rolling
> resistance of tires in god condition is almost entirely hysteretic
> losses in elastomers, tread, tube, sidewall rubber and inter-ply
> binders.
That makes sense.
> I have not seen a tire develop separated cords even when worn through
> the tread exposing these cords.
I've had several tires suffer cord separation, always along the bias
angle between adjacent cords. Two Ritchey Tom Slicks in 700 x 25, two
or three Tom Slicks in 26 x 1.0. One end of the separation always went
to or started from the pronounced sipe along the side of the tires, and
the cords would separate enough to allow the inner tube to poke through.
(I no longer use Tom Slicks). On a 65 miler on Sunday with a couple of
friends, I had a similar failure with a Panaracer Pasela 26 x 1.25 but
the cord separation was located in the center of the tread, about 5 mm
long and again oriented along the bias angle and between adjacent cords.
The edges wore through the inner tube causing a flat. That was how I
discovered the casing failure. I booted it and was able to ride home
with no further problems.
I've not had other people tell me of similar failures, so I wonder if it
is something specific to me. I inflate the tires to the maximum marked
on the sidewall using a Silca Super Pista pump which, as far as I know,
has an accurate gauge within a few PSI (at least when compared to
another Presta valve gauge I have). The failures have been in tires
used on the front as well as the rear wheel. There has always been at
least half of the tread left on the tire. There has been no visible
external damage such as a cut.
|
| |
Date: 29 May 2007 22:31:06
From: Kinky Cowboy
Subject: Re: faster casing = faster tires?!@
|
On 29 May 2007 13:50:30 -0700, bfd <bfd853@yahoo.com > wrote:
> So, the question is how do you
>tell whether a tire is build around *fast* casing or "slow" casing?
>Or, is this just a myth?
Casing thread count, casing material, number of plies on sidewall and
under tread, and the presence and thickness of a rubber layer on the
sidewall are all relevant.
Compare this fast tyre
http://www.veloflex.it/products_tyres_details.htm
with this slow one
http://www.conti-online.com/generator/www/de/en/continental/bicycle/themes/tires/race/grand_prix_4_season/grand_prix_4_season_en.html
As you can see, the Conti has many extra directory layers in the
URI... :-)
Kinky Cowboy*
*Batteries not included
May contain traces of nuts
Your milage may vary
|
|
