Real Rolling Resistance of Tubulars
Ironhanglider
would judder my way around race courses at 130 - 140psi thinking that
I was saving energy.
More recently I have been enlightened to and realise that more is not
necessarily better, particularly on the course roads that I race on
around here. I understand that this is due to the suspension effect
of the tyres and that beyond a certain sweet spot the jarring action
is costing energy. I also understand that the sweet spot is variable
according to tyre construction and width and the weight of the rider.
I now ride with less pressure despite being nearly 30kg heavier than I
was in the 80s.
Similarly I used to accept that the hysterical nature of (road) glue
would cause losses in energy. However tubular tyres are more
compliant and when I first rode them I thought that I had a slow leak
due to the relatively cushy ride at my usual pressures. At the time I
thought beauty, this means I can ride even higher pressures, (and at
the same time saving rotating weight and having a more poseur-worthy
bike).
A recent test that I have seen reported seemed to focus on the rolling
resistance of a clincher tyre at various pressures, which highlighted
that the sweet spot exists and that the resistance changes quite
dramatically with pressure, particularly when it is more than
necessary.
My question is whether the losses caused by the hysteresis of the glue
are somehow cancelled out by the gains from the more compliant ride
and how much so? Are tubulars of similar construction (such as
Vittoria Corsa and Open Corsa tyres) at the same pressures actually
faster than clinchers? Since I reckon that the Tubulars feel like
about 10psi less, does that mean that the sweet spot is actually a
little higher in pressure. If both tubular and clincher are at their
sweet spots what is their relative resistance then?
Jobst Brandt
> I used to believe in the mantra of more pressure = less resistance
> and would judder my way around race courses at 130 - 140psi thinking
> that I was saving energy.
> More recently I have been enlightened to and realise that more is
> not necessarily better, particularly on the course roads that I race
> on around here. I understand that this is due to the suspension
> effect of the tyres and that beyond a certain sweet spot the jarring
> action is costing energy. I also understand that the sweet spot is
> variable according to tyre construction and width and the weight of
> the rider. I now ride with less pressure despite being nearly 30kg
> heavier than I was in the 80s.
This is not a religious exercise, the cause of tire rolling resistance
being a principal that is well researched and understood. RR is
caused by hysteretic losses in elastomers that in tires are in the
inner tube, tire casing and tread rubber. Any flexing in these
components causes hysteretic losses in the elastomers.
> Similarly I used to accept that the hysterical nature of (road) glue
> would cause losses in energy. However tubular tyres are more
> compliant and when I first rode them I thought that I had a slow
> leak due to the relatively cushy ride at my usual pressures. At the
> time I thought beauty, this means I can ride even higher pressures,
> (and at the same time saving rotating weight and having a more
> poseur-worthy bike).
If you observe the wear marks on tubular tire base tapes, the part
between the tire casing and the rim to which it is glued, you will
notice that there is motion and this motion causes the high viscosity
tire adhesive to displace with every loaded rotation. For this reason
hard glue was invented to reduce these losses for tires that do not
require manual quick changes in a road race where there is no reserve
wheel with another well attached tire. Base tapes on road tubular
tires wear through to the tire casing and on long touring use cause
tire failure.
> A recent test that I have seen reported seemed to focus on the rolling
> resistance of a clincher tyre at various pressures, which highlighted
> that the sweet spot exists and that the resistance changes quite
> dramatically with pressure, particularly when it is more than
> necessary.
> My question is whether the losses caused by the hysteresis of the glue
> are somehow canceled out by the gains from the more compliant ride
> and how much so? Are tubulars of similar construction (such as
> Vittoria Corsa and Open Corsa tyres) at the same pressures actually
> faster than clinchers? Since I reckon that the Tubulars feel like
> about 10psi less, does that mean that the sweet spot is actually a
> little higher in pressure. If both tubular and clincher are at their
> sweet spots what is their relative resistance then?
The "sweet spot" is the highest inflation pressure the tire will
safely hold and the rider can accept for the roughness of the course.
I see that you are not looking at scientific evidence in your
analysis. Rolling resistance is not a religious concept.
Jobst Brandt
Frank Krygowski
I think Jobst is defining rolling resistance overly strictly, limiting
the definition to hysteresis losses within the tire.
Fine. If we do that, then the factors that consume rider input power
on level ground are these:
1) Air resistance
2) Mechanical rolling friction in the various bearings, including the
chain
3) Jobst's tire hysteresis, with all the subtle details he loves,
AND:
4) Suspension losses, in which bike+rider mass is lifted and shaken by
imperfections in the road surface.
Like it or not, the tires are the main mechanism for fighting item
#4. And like it or not, tires chosen to reduce item #3 to an absolute
minimum will _increase_ losses from item #4, at least when riding on
any surface rougher than a steel drum or a smooth linoleum floor.
This tells me there is, indeed, a "sweet spot" for tire width and tire
pressure. And it likely varies depending on load and road roughness.
If it were otherwise, we'd dispense with pneumatic tires and ride hard-
tired safeties.
Think about that: Isn't it odd that the most respected tests of tire
rolling resistance would tell us to dispense with Dr. Dunlop's
inventions? Doesn't that prove that some other test is necessary?
- Frank Krygowski
thirty-six
Well said.
Kinky Cowboy
<frkr...@gmail.com> wrote:
>Think about that: Isn't it odd that the most respected tests of tire
>rolling resistance would tell us to dispense with Dr. Dunlop's
>inventions? Doesn't that prove that some other test is necessary?
This isn't so. A solid rubber tyre of any durometer with enough grip
to be useful flexes so much throughout it's body that using high
pressure air to replace bulk rubber makes sense even if the suspension
displacement ends up the same.
One could hypothesise a thin tread band of the same thickness as
currently used on pneumatic tyres applied to an extremely rigid body,
such as a solid steel wheel, and that should indeed provide lower
rolling resistance than pneumatic tyres on a steel drum test, but the
ride and handling would be unacceptable even to track racers, and it
seems that supporting the tread band with the same compliance as is
currently provided by the air chamber would add significantly to the
system mass.
Kinky Cowboy*
*Batteries not included
May contain traces of nuts
Your milage may vary
carl...@comcast.net
wrote:
Dear Kinky,
Useful solid rubber tires were noticeably slower than the first crude
pneumatics.
Racing times improved dramatically when our great-grandfathers
switched from riding safeties with solid rubber tires to Dr. Dunlop's
pneumatic tires.
Handicaps of 100 yards for pneumatics in a mile race were common
before solid tires vanished from the racing scene.
Even highwheelers tried the pneumatics for speed.
Cheers,
Carl Fogel
dusto...@mac.com
Lots of different sweet spots, I'd guess, if you include width and
pressure (and construction incl. weight, sidewall/tread thickness,
tread pattern, whatever.
Old data (from The Sewup Age) I've seen showed a curve representing
"advantage of increasing pressure" flattening out at about 110-115
psi. Which intersects another "curve" of sorts, seeing people over-
inflate tubular tires, back in the day, and not get to the end of
their 40k ITT without flatting.
I'm sure this tendency has continued into The Age of Clinchers.
("Well, why does the pump gauge go to 180 then???")
Note, Jobst's oft-stated method of gluing on sewups, which is to put
cement on the rim only, deliberately in service of easier removal for
flat changing, does not produce the bond (sometimes or often <g>)
achieved by gluing both tire and rim before tire mounting, where
(often, especially after use) a tire might be bonded so tightly to the
rim as to be difficult-to-impossible to remove without tools, and/or
ripping the base tape off the tire.
That's a trade-off user choice IMHO.
However, this added necessary parting force is plain evidence of a
much tighter bond than one that allows a tubular to be easily removed
for service, which might affect the amount of "squirm", influencing
rolling resistance and indeed, base tape wear.
--D-y
thirty-six
What's base tape wear? ;-)
Jobst Brandt
> Note, Jobst's oft-stated method of gluing on sew-ups, which is to
> put cement on the rim only, deliberately in service of easier
> removal for flat changing, does not produce the bond (sometimes or
> often <g>) achieved by gluing both tire and rim before tire
> mounting, where (often, especially after use) a tire might be bonded
> so tightly to the rim as to be difficult-to-impossible to remove
> without tools, and/or ripping the base tape off the tire.
That's a bold faced lie! I have never suggested such a tubular gluing
method. Unless shellac (hard glue for track) is used, road glues are
made for manually changing tires when needed. From this I see the
writer did not ride tubulars in the days when all riders on good
bicycles used them, there being no (reliable) light weight clinchers.
> That's a trade-off user choice IMHO.
> However, this added necessary parting force is plain evidence of a
> much tighter bond than one that allows a tubular to be easily
> removed for service, which might affect the amount of "squirm",
> influencing rolling resistance and indeed, base tape wear. --D-y
Anonymous must have written this from hearsay and imagination.
Jobst Brandt
Michael Press
<ed514b32-8d30-4ffc...@u26g2000yqu.googlegroups.com>,
"dusto...@mac.com" <dusto...@mac.com> wrote:
More glue will not reduce flow in the glue induced
by the cyclic load in use. That is to say: gluing
both rim and tire will not reduce tire squirm on
the rim. The glue remains a viscous fluid no matter
how much you apply.
--
Michael Press
thirty-six
> In article
> <ed514b32-8d30-4ffc-b777-a0bd96ee3...@u26g2000yqu.googlegroups.com>,
The optimum is that which stays adhered to both surfaces and provides
cohesion, but no more. Tubasti seems ideal to me, because despite an
uneven surface, with a little extra middle glue, and high installation
pressure, the cement oozes to form a bead, with the minimum cement
between rim and tyre. Not enough will probably encourage wear and
slippage, too much may encourage slipping due to reduced shear
strength with increased thickness. The bead formation may indeed b
the reason for mi=nimal wear of my rims/tapes. The glue gets a little
grey at the edge after many thousands of miles.
dusto...@mac.com
> In article
> <ed514b32-8d30-4ffc-b777-a0bd96ee3...@u26g2000yqu.googlegroups.com>,
>
>
>
>
>
Well, lots more glue, besides flying all over the place incl. rim
sidewalls, not good for smooth braking, would seem to increase squirm,
depending on just how close to "solid" the glue cures out to.
I did say "might"; based on how easy it is to remove a, let's call it
"lightly glued" tire vs. one glued to stay on. Makes sense to me that
a tire that rips right off would squirm more than one that requires a
lot of force to peel off, whatever the actual thickness of cement.
--D-y
dusto...@mac.com
> anonymous wrote:
> > Note, Jobst's oft-stated method of gluing on sew-ups, which is to
> > put cement on the rim only, deliberately in service of easier
> > removal for flat changing, does not produce the bond (sometimes or
> > often <g>) achieved by gluing both tire and rim before tire
> > mounting, where (often, especially after use) a tire might be bonded
> > so tightly to the rim as to be difficult-to-impossible to remove
> > without tools, and/or ripping the base tape off the tire.
>
> That's a bold faced lie!
No, it's not.
> I have never suggested such a tubular gluing
> method.
Which one? Glue on both tire and rim (choice A); or glue on rim only
(choice B)?
> Unless shellac (hard glue for track) is used, road glues are
> made for manually changing tires when needed.
That sounds right. Track riders might want/need better adhesion; plus
they might more easily get a spare wheel than someone "on the road"
especially who isn't racing (meaning, no tech support with spare
wheels along for the ride). Trackies certainly wouldn't be happy with
riding a wheel with a spare tire mounted, unless a cement could be
found that allowed spares to stick 100% and immediately to a rim.
> From this I see the
> writer did not ride tubulars in the days when all riders on good
> bicycles used them, there being no (reliable) light weight clinchers.
Oh yes I did too ride tubulars in the bad old days-- starting in 1972,
July, when I got my first bike with slotted-sidewall Nisi rims and
cheapo cotton sewups-- one of which was branded "Cody", IMS.
> Anonymous must have written this from hearsay and imagination.
Suggest you get past your problem with "anonymous" and stop writing
from knee-jerk reaction, because what I said was true. IMS, the words
were-- after I suggested roughing up a base tape to get the cement to
stick to base tape, and not to a latex coating on the base tape, in
order to glue base tape securely to the rim bed-- "just put it (the
tire) on there". Impatient with those who don't agree. And gosh, this
last time here I was nice as apple pie even though I strongly disagree
with doing anything that might interfere with getting the best bond
possible between tire and rim.
So, does "just put it on there" ring a bell?
--D-y
Jobst Brandt
Tim McNamara
<5a5461e2-830f-4f1c...@k39g2000yqb.googlegroups.com>,
Ironhanglider <cameron...@mac.com> wrote:
Tubular hysteria aside, the answer is maybe. In some cases. Not in
others. This was plotted out years ago using the tires available at the
time. It would be nifty to have it replicated with current tires and
glues, although maybe it has been and I am unaware.
http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html
--
That'll put marzipan in your pie plate, Bingo.
Jobst Brandt
>> glue are somehow canceled out by the gains from the more compliant
>> ride and how much so? Are tubulars of similar construction (such
>> as Vittoria Corsa and Open Corsa tyres) at the same pressures
>> actually faster than clinchers? Since I reckon that the Tubulars
>> feel like about 10psi less, does that mean that the sweet spot is
>> actually a little higher in pressure. If both tubular and clincher
>> are at their sweet spots what is their relative resistance then?
> Tubular hysteria aside, the answer is maybe. In some cases. Not in
> others. This was plotted out years ago using the tires available at
> the time. It would be nifty to have it replicated with current
> tires and glues, although maybe it has been and I am unaware.
http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html
So why does it take eons for this information to sink in? This stuff
has been on wreck.bike often, especially back then when many riders
were still on these tubulars and Avocet tried to show comparisons with
IRC tire tests. I drew up the original cross sections and defined the
slick tire for Avocet (IRC) tires at the time, knowing that tread
squirm was a large part of many poor RR tires.
Headway was made then, but other Mfg's back slid and put pseudo
patterned tread on their tires, like Continental with its little
dimples on the sidewalls and failure to put a chafing strip on the
tire bead.
Jobst Brandt
Jay Beattie
With all due respect to the chart, the Vittoria CX was a faster tire
than the Avocet 30 28mm. I owned both and generally raced on CXs and
CGs. Could have been a weight issue, including rim weight. The
Clement Seta was never my favorite because (apart from price) it
always felt too squishy, which is a technical term for too squishy. I
know this is terribly non-scientific myth and lore, so you can let me
have it -- but I'm sticking to my story. -- Jay Beattie.
thirty-six
As I recall, he was partial to applying the tyre onto wet cement,
still loaded with solvent. This is bound to squirm under load and be
affected by heat, the solvent is there to enable easy application only
and must evaporate before assembly of the joint. Only shellac differs
in this respect where some solvent must remain, leaving the surface
slightly tacky. All other cements are contact adhesives and as such,
need to be assembled dry for greatest cohesion.
> That's a trade-off user choice IMHO.
> However, this added necessary parting force is plain evidence of a
> much tighter bond than one that allows a tubular to be easily removed
> for service, which might affect the amount of "squirm", influencing
> rolling resistance and indeed, base tape wear.
I think it be a poor choice. Carrying a tyre lever(or three) is
something generally done by high pressure users, so it is no further
inconvenience to carry a single one with well glued on tubular tyres.
I do so, combined with a 15mm spanner for my wheel nuts. I am unable
to explain JB's reasonings on tyres other than they being simply
irrational or for commercial reasons.
James
> In article
> <5a5461e2-830f-4f1c-a73d-3808a3ba9...@k39g2000yqb.googlegroups.com>,
Anyone know how the test was performed?
JS.
thirty-six
The test was designed to show the superiority of one tyre in a straigh
tline on a smooth steel drum. There is no indication of load.
Note "This effect can be measured in various ways, the most obvious of
which is to measure drag directly with a scale, a method that is
difficult." I have never found using a spring balance difficult. If
you want to know how tyres compare on a road, measure them on a road
with something simple, such as a spring balance drawing a loaded
trailer with the tyre under test.
Stephen Bauman
[snip]
>
>Base tapes on road tubular tires
> wear through to the tire casing and on long touring use cause tire
> failure.
>
[snip]
Huh?????
I rode tubulars exclusively until 25 years ago, commuting, training, club
rides, touring, etc. I averaged around 5000 miles per year. I never
experienced noticeable noticeable base tape wear due to friction. I did
experience base tape deterioation due to old age, when tire and base tape
dried out after about 5 years. There were some tubulars that I stored,
forgot about and rediscovered many years later. Rim friction was not a
factor because these tubulars had never been ridden.
I used Clement cold pressed (hand made) tubulars, usually Del Mundo's,
Corsa Speciale's, Paris-Roubaix's and Criterium's. I also used Clement
Extra Mastice Gutta Strada in the red, white and green tube. The red glue
that stained your pinky for the entire season.
I once got more than 2000 miles out of a tubular without a flat, just so
we are clear about what constitutes "long" touring. No base tape damage,
just a very worn tread and the casing hole from the nail that finally
killed it.
There is some reference to base tape damage caused by glues that were not
designed for tubular use.
http://www.worldclasscycles.com/dupont_fasttack.htm
The problem was that the glue solvent also dissolved the contact cement
that held the base tape to the tire. One can certainly appreciate that
chafing between a loose base strip and the tire carcass would eventually
cause tire failure.
Look at the price list for my reason for not riding tubulars today
http://www.worldclasscycles.com/tubular_tires_only.htm
I dropped out when prices hit $37.50 per tire.
Stephen Bauman
Tim McNamara
<5e876ce4-db22-4b14...@a6g2000pro.googlegroups.com>,
James <james.e...@gmail.com> wrote:
This is a repeat of a very old discussion, the last iteration probably
having happened before you started reading the newsgroup. Hopefully
this link will provide most of the information:
http://www.terrymorse.com/bike/rolres.html
My recollection is that the tests were done by IRC, the manufacturer,
using the standard methodology: a large spinning drum and the wheel in
a fixture pressing the tire onto the drum at a specified load.
thirty-six
> Look at the price list for my reason for not riding tubulars today
In so doing it is hard for me not to notice the wide range of widths
available for road tyres. It would probably be in order to have eight
different sprint rims to cover the range appropriately so as to give
a good bond with a matched tyre bed profile. Except I would be
unlikely to use anything smaller than 23mm myself, that would mean 4
different tyre bed profiles. Take it that you can add tape, so taking
a one size smaller tyre, that is actually only two different rims(not
that bad after all). Cheap tyres with raised seams need a recess
along the centre of the tyre bed as well as the normal requirement of
the tyre bed matching the tyre radius.
>
> http://www.worldclasscycles.com/tubular_tires_only.htm
>
> I dropped out when prices hit $37.50 per tire.
Did you not repair your tyres?
Sir Ridesalot
Hi there.
Yellow Jersey sells tubs at 3 for $50.00 which appears to be a great
deal. Or do you people think hat those tires are too inexpensive to be
any good?
Part of the sales blurb on the site:
We've sold hundreds of our Thai-made d'Alessandro tubular tires over
the past few years, bringing affordable, dependable tubulars back to
the American rider. Unfortunately, the d'Alessandro label is no
more. So, we researched all the available tires and, after testing,
committed to the late-90s Clement TT tubular.
"Nice, round Thai casing of fine-weave cotton but with a smoother,
more modern tread, premium long-staple cotton wound to a high 127tpi
thread count and a trendy black sidewall. They are a true 300g with a
nice hefty butyl tube so you'll find they hold air for weeks. (That
makes a difference for us commuters!) Same 21.5mm tire casing, same
brass removable core valves, same factory, new label"
Cheers from Peter
Stephen Bauman
>
> Did you not repair your tyres?
I needed something to do on those long winter nights :=) I even got a
sewing awl to duplicate the chain stitch.
I'd repair the tubulars during the off season. That meant I'd need a
reserve of about 10 tires for the season. I'd start each season with 5
new tires. The latex tubes would shatter rather than puncture when they
became brittle after a couple of seasons. There was always a need to
replenish between 5 and 10 tires per season.
Stephen Bauman
thirty-six
> On Fri, 02 Jul 2010 08:54:04 -0700, thirty-six wrote:
>
> > Did you not repair your tyres?
>
> I needed something to do on those long winter nights :=) I even got a
> sewing awl to duplicate the chain stitch.
>
> I'd repair the tubulars during the off season. That meant I'd need a
> reserve of about 10 tires for the season. I'd start each season with 5
> new tires. The latex tubes would shatter rather than puncture when they
> became brittle after a couple of seasons.
Surprised. Seems like you didn't get your wear out of them. What do
you think made the tubes brittle? I've used latex tubes with covers
and the tubes seemed good for three or four years when I used them and
still seemed good about ten years later. One I found eighteen years
after purchase (and used) had deteriorated and broke when stretched.
This had been in a polythene tub with other narrow butyl tubes from
the time. The butyl tubes seem fine except for one valve stem which
separated.
James
> In article
> <5e876ce4-db22-4b14-816d-d4bf86eaf...@a6g2000pro.googlegroups.com>,
Mmm. I thought as much. All I see is a test performed on a smooth
steel drum, not a drum coated with various grades of "road". How can
anyone extrapolate that road surface can be discounted from the
overall picture? Seems very inconclusive to me. The gauntlet is
thrown down.
Even if the road surface has nothing to do with actual rolling
resistance, it certainly has something to do with rider perceived
effort. Friends of mine who have ridden/raced in Europe, where the
roads are all far smoother than here, claim they can easily achieve
1-2kph faster than back home.
I realise this has been discussed before, like helmets and tubular
glue, but maybe it's time the advocates of RR being losses in rubber
alone and scientific tests, step up to the plate and prove the rest of
us wrong, or at least explain the perceived difference felt by so many
riders.
Regards,
James.
Stephen Bauman
>
>
> Surprised. Seems like you didn't get your wear out of them. What do
> you think made the tubes brittle? I've used latex tubes with covers
> and the tubes seemed good for three or four years when I used them and
> still seemed good about ten years later. One I found eighteen years
> after purchase (and used) had deteriorated and broke when stretched.
> This had been in a polythene tub with other narrow butyl tubes from the
> time. The butyl tubes seem fine except for one valve stem which
> separated.
I also went through 3 or 4 rims per year. I didn't baby the equipment.
Now that I've become fat and slow, I have enough time to see road hazards
and avoid them.
I also did more than my share of rain and night riding. Also, this was
before there was a mandatory deposit on glass bottles. The tubulars would
get cuts without flatting. I wasn't as diligent as I should have been in
trying to close the cuts, nor in making sure the sidewall latex coating
was fresh. The result was that contamination reached the tubes and
prematurely aged them. You could tell from the color, where the tubes had
been exposed, aged and became brittle.
Stephen Bauman
Mark Cleary
Don't underestimate the religious aspect of the tire exercises. I had a
flat once and pull out my trusty tube to change it thinking I will be
done in minutes. Well sure enough my value stem was too short for my
30mm rims and no way to patch the puppy. I might add I did not have my
cell phone either. I thought " Oh Lord I sure could use some help."
Within not 2 minutes a fellow pulls up in a truck who happened to be a
member of the parish. He says, "Deacon you need any help?" I sure could,
"Tom can you give a lift home I am about 7 miles out?" We get the bike
in the truck and I am home in a few minutes. I am not making this up is
happened.
Moral of the story is to make sure you get the proper valve stem length,
carry a cell phone, and when in trouble pray. Don't think this had much
to do with the original question but seem to bring out the religious
aspect of tires and bikes. I must say though that the rolling resistance
of a flat tire on skinny road bike rims is pretty high. The amount of
gray matter in this particular deacon's head probably is not too high so
had to have a warning. Now I have the correct tube but maybe the next
time my co2 inflater will go bad. Also there is zero rolling resistance
on the tire in the back of a truck riding home.
I am on roll.................
Jobst Brandt wrote:
> Cameron Ermert wrote:
>
>> I used to believe in the mantra of more pressure = less resistance
>> and would judder my way around race courses at 130 - 140psi thinking
>> that I was saving energy.
>
>> More recently I have been enlightened to and realise that more is
>> not necessarily better, particularly on the course roads that I race
>> on around here. I understand that this is due to the suspension
>> effect of the tyres and that beyond a certain sweet spot the jarring
>> action is costing energy. I also understand that the sweet spot is
>> variable according to tyre construction and width and the weight of
>> the rider. I now ride with less pressure despite being nearly 30kg
>> heavier than I was in the 80s.
>
> This is not a religious exercise, the cause of tire rolling resistance
> being a principal that is well researched and understood. RR is
> caused by hysteretic losses in elastomers that in tires are in the
> inner tube, tire casing and tread rubber. Any flexing in these
> components causes hysteretic losses in the elastomers.
>
>> Similarly I used to accept that the hysterical nature of (road) glue
>> would cause losses in energy. However tubular tyres are more
>> compliant and when I first rode them I thought that I had a slow
>> leak due to the relatively cushy ride at my usual pressures. At the
>> time I thought beauty, this means I can ride even higher pressures,
>> (and at the same time saving rotating weight and having a more
>> poseur-worthy bike).
>
> If you observe the wear marks on tubular tire base tapes, the part
> between the tire casing and the rim to which it is glued, you will
> notice that there is motion and this motion causes the high viscosity
> tire adhesive to displace with every loaded rotation. For this reason
> hard glue was invented to reduce these losses for tires that do not
> require manual quick changes in a road race where there is no reserve
> wheel with another well attached tire. Base tapes on road tubular
> tires wear through to the tire casing and on long touring use cause
> tire failure.
>
>> A recent test that I have seen reported seemed to focus on the rolling
>> resistance of a clincher tyre at various pressures, which highlighted
>> that the sweet spot exists and that the resistance changes quite
>> dramatically with pressure, particularly when it is more than
>> necessary.
>
>> My question is whether the losses caused by the hysteresis of the glue
>> are somehow canceled out by the gains from the more compliant ride
>> and how much so? Are tubulars of similar construction (such as
>> Vittoria Corsa and Open Corsa tyres) at the same pressures actually
>> faster than clinchers? Since I reckon that the Tubulars feel like
>> about 10psi less, does that mean that the sweet spot is actually a
>> little higher in pressure. If both tubular and clincher are at their
>> sweet spots what is their relative resistance then?
>
> The "sweet spot" is the highest inflation pressure the tire will
> safely hold and the rider can accept for the roughness of the course.
> I see that you are not looking at scientific evidence in your
> analysis. Rolling resistance is not a religious concept.
>
> Jobst Brandt
--
Deacon Mark Cleary
Epiphany Roman Catholic Church
dusto...@mac.com
I had some del Mondo silks that I rode sparingly, and put away
carefully, back in days of no money.
About the third season, I started to get them ready for a Spring ride,
and they were rotted.
What a waste. Lesson learned.
--D-y
Frank Krygowski
>
> I had some del Mondo silks that I rode sparingly, and put away
> carefully, back in days of no money.
> About the third season, I started to get them ready for a Spring ride,
> and they were rotted.
> What a waste. Lesson learned.
I was lent a pair of those same tires (on matching wheels) by a friend
trying to convince me that, despite my days of no money, they were
worth the price.
I tested them on a ride on a foggy Saturday morning, and thought "Yes,
they feel nice, but I don't think the improvement is worth the
price." I parked the bike outside as I went inside to cool off and
refresh my thirst.
Then the hot Georgia sun came out. And I heard a tremendous BANG.
The Clement silk tire had blown out right on the top, right through
the tread.
What a waste. Lesson learned. Continue riding clinchers.
- Frank Krygowski
thirty-six
I do remember now seeing brown areas on my latex tubes where the tyre
tread had been cut and not closed. Also some minor deterioration over
the rim holes, possibly a minor reason for corking HP rims.
Sir Ridesalot
>
> - Show quoted text -
Hi there.
About fifteen kilometres from where I live there is a section of road
that has a really weird section of asphalt on it. It looks normal but
when you first turn onto this section of road you think you have a
slow leak or have flatted because the increase in rolling resistance
is so high.
I have seen many cyclists stop shortly after geting onto this stretch
of road because they thought thy had flatted. It's really wird because
the road surface *LOOKS* normal.
Cheers from Peter
Peter Cole
> Jobst,
>
> Don't underestimate the religious aspect of the tire exercises. I had a
> flat once and pull out my trusty tube to change it thinking I will be
> done in minutes. Well sure enough my value stem was too short for my
> 30mm rims and no way to patch the puppy. I might add I did not have my
> cell phone either. I thought " Oh Lord I sure could use some help."
> Within not 2 minutes a fellow pulls up in a truck who happened to be a
> member of the parish. He says, "Deacon you need any help?" I sure could,
> "Tom can you give a lift home I am about 7 miles out?" We get the bike
> in the truck and I am home in a few minutes. I am not making this up is
> happened.
>
> Moral of the story is to make sure you get the proper valve stem length,
> carry a cell phone, and when in trouble pray. Don't think this had much
> to do with the original question but seem to bring out the religious
> aspect of tires and bikes. I must say though that the rolling resistance
> of a flat tire on skinny road bike rims is pretty high. The amount of
> gray matter in this particular deacon's head probably is not too high so
> had to have a warning. Now I have the correct tube but maybe the next
> time my co2 inflater will go bad. Also there is zero rolling resistance
> on the tire in the back of a truck riding home.
>
> I am on roll.................
Personally, I'd rather not rely on divine assistance. Those who have
done any touring or brevet riding realize (sometimes the hard way) that
planning and preparation are necessary, particularly for predictable
things like flats. 7 miles from home is hardly terra incognita, try 70
miles and make it 3 AM, and raining, make the rain cold, make the road
empty and put 0 bars on the cell phone.
thirty-six
That's a case (without proper resources) to ride the rim.
dusto...@mac.com
Unfortunately, that seems to have been a common experience with
Clement cotton sewups, back in the day. The silks were supposed to be
much stronger (also more supple and generally more magical, too). By
the mid-80's the Vittoria CG/CX's were available (in my world) and
definitely the choice tire(s) for some uses, better than the clinchers
I remember in those years, definitely not known to blow like that even
here in the Texas (Austin) sun (30° 16' 0" N / 97° 44' 34" W). But
yeah, still more expensive and more fragile (maybe! <g>) than
available clinchers.
--D-y
Stephen Bauman
The fact that the tire blew through the tread is indicative that the
carcass had become damaged. If it was simply a question of too much
pressure (due to baking in the Georgia sun), then the expected weak link
would have been near the stitching.
Clinchers are not immune to blowouts. I learned that lesson on my first
club ride with clinchers. It was the Montauk Century and rain was
forecast. The ride hugged the coast. Beach sand would blow onto the road;
the sand would be picked up by the tire and lodge on the outer side edge
between tire and rim. This sand would work a hole into the bare sidewall
over the course of the 115 mile ride. Such holes were extremely difficult
to boot because they were close to the stitching. I figured why wreck a
good tubular and decided to make my clincher debut.
My trouble-free experience with clinchers lasted 90 miles - them boom. I
carried spare tubes but this was before foldable tires. I was very lucky.
I had just passed the only bike shop that was open in those Sunday Blue
Law days. I walked back the 1/2 mile and got a new tire and tube. It was
also when 700C's were a rarity, with 27" tires being the vogue. The only
700C that shop had was a narrow Wolber that rode like garden hose. It was
a very bumpy last 25 miles. I've always carried a foldable spare after
they became available.
Lesson learned? It would have been a simple 5 minute tire change had I
been riding tubulars. Instead, I got to walk back the 1/2 mile to the
shop in my cycling shoes with slotted metal cleats. I also got to do a
wind sprint to catch up to the group with which I'd been cycling after
the repair.
Stephen Bauman
thirty-six
> On Jul 2, 10:08 pm, Frank Krygowski <frkry...@gmail.com> wrote:
>
>
>
> > On Jul 2, 9:31 pm, "dustoyev...@mac.com" <dustoyev...@mac.com> wrote:
>
> > > I had some del Mondo silks that I rode sparingly, and put away
> > > carefully, back in days of no money.
> > > About the third season, I started to get them ready for a Spring ride,
> > > and they were rotted.
> > > What a waste. Lesson learned.
>
> > I was lent a pair of those same tires (on matching wheels) by a friend
> > trying to convince me that, despite my days of no money, they were
> > worth the price.
>
> > I tested them on a ride on a foggy Saturday morning, and thought "Yes,
> > they feel nice, but I don't think the improvement is worth the
> > price." I parked the bike outside as I went inside to cool off and
> > refresh my thirst.
>
> > Then the hot Georgia sun came out. And I heard a tremendous BANG.
> > The Clement silk tire had blown out right on the top, right through
> > the tread.
>
> > What a waste. Lesson learned. Continue riding clinchers.
>
> Unfortunately, that seems to have been a common experience with
> Clement cotton sewups, back in the day.
Probably due to the misconception that tubulars can hold higher
pressures, so should be used as high as you get them to minimise
rolling resistance. I remember when eventually switching to
(training) tubulars being laughed at because I intended to run them at
110psi and more. I was seriously advised against using such
ludicrously high pressures because of tearing when crossing gratings
and the like. The advice was correct, when crossing gratings through
a corner, the lower pressure(90psi or less) enables the wheel to
continue to track a stable curve. Taking the tyre up to 130psi meant
it would skip in the corners where there are gratings.
Secondarily, silks have lower carcass resistance due to the finer
threads made from a smooth staple. Silk threads slide. Reputedly to
be poor wet weather performers because of the tendency to split when
wet. I don't know, I suspect it was a matter of poor maintenance of
the latex sidewalls. Perhaps (covered) velodrome specific(thin
tread, no sidewall protection) tyres were used outdoors. I can
imagine this being tempting for time trial record chasers, and deemed
acceptable for the rich lunatic racers
Tom Sherman °_°
> Jobst,
>[...]
A. Top Posting.
Q. What is the greatest sin on Usenet?
--
Tom Sherman - 42.435731,-83.985007
thirty-six
wrote:
> On 7/2/2010 8:31 PM, Mark Cleary wrote:
>
> > Jobst,
> >[...]
>
> A. Top Posting.
>
> Q. What is the greatest sin on Usenet?
nitpicking
Jobst Brandt
> A. Top Posting.
> Q. What is the greatest sin on Usenet?
Too bad. Most top posters have no idea about logical sequence for Q&A
even in email writing. Their messages are hard to follow but they
have most likely unscrambled such thinking in the muddle of their
brain. Unfortunately much of it makes no sense. It's rude to expect
others to think similarly.
Jobst Brandt
thirty-six
windows and left handed threads?" and "Does a Spanish omelette have to
include potatoes?"
Tim McNamara
<14ad3245-10b4-460e...@n19g2000prf.googlegroups.com>,
James <james.e...@gmail.com> wrote:
Not so much. This is also an old conversation. See below.
> Even if the road surface has nothing to do with actual rolling
> resistance, it certainly has something to do with rider perceived
> effort. Friends of mine who have ridden/raced in Europe, where the
> roads are all far smoother than here, claim they can easily achieve
> 1-2kph faster than back home.
>
> I realise this has been discussed before, like helmets and tubular
> glue, but maybe it's time the advocates of RR being losses in rubber
> alone and scientific tests, step up to the plate and prove the rest
> of us wrong, or at least explain the perceived difference felt by so
> many riders.
Rolling resistance is a property of the tire. The smooth drum test is
the best tool we have for isolating and quantifying that property.
Rolling resistance as a property of the tire won't change significantly
from one surface to the next.
The losses on smoother versus rougher surfaces are suspension losses;
these are much harder to quantify. The occasionally maligned Jan Heine
has made some efforts in this direction using a Tune Power Tap hub and
has published those in his magazine, Bicycle Quarterly.
Frank Krygowski
>
>
> Rolling resistance is a property of the tire. The smooth drum test is
> the best tool we have for isolating and quantifying that property.
> Rolling resistance as a property of the tire won't change significantly
> from one surface to the next.
>
> The losses on smoother versus rougher surfaces are suspension losses;
> these are much harder to quantify. The occasionally maligned Jan Heine
> has made some efforts in this direction using a Tune Power Tap hub and
> has published those in his magazine, Bicycle Quarterly.
Yes, for bicycles, rolling resistance is usually defined as a property
of the tire - i.e., most people seem to limit the definition to the
resistance due to tire hysteresis.
But most people who define rolling resistance that way seem to give no
mention to suspension losses. Yet suspension losses are often larger
than hysteresis losses, and are greatly influenced by tire
characteristics.
Again, if this thinking were extended just a little, it would lead one
to abandon pneumatic tires. That indicates it's mistaken. Suspension
losses ought to be accounted for somewhere. A "rolling resistance"
test seems like the logical place to do so, even if it calls for some
redefinition.
- Frank Krygowski
James
> In article
> <77c1db81-fac0-4c98-becf-0c791dd0a...@k39g2000yqd.googlegroups.com>,
> Frank Krygowski <frkry...@gmail.com> wrote:
>
>
>
> > On Jul 5, 1:42 am, Tim McNamara <tim...@bitstream.net> wrote:
>
> > > Rolling resistance is a property of the tire. The smooth drum test
> > > is the best tool we have for isolating and quantifying that
> > > property. Rolling resistance as a property of the tire won't
> > > change significantly from one surface to the next.
>
> > > The losses on smoother versus rougher surfaces are suspension
> > > losses; these are much harder to quantify. The occasionally
> > > maligned Jan Heine has made some efforts in this direction using a
> > > Tune Power Tap hub and has published those in his magazine, Bicycle
> > > Quarterly.
>
> > Yes, for bicycles, rolling resistance is usually defined as a
> > property of the tire - i.e., most people seem to limit the definition
> > to the resistance due to tire hysteresis.
>
>
> > But most people who define rolling resistance that way seem to give
> > no mention to suspension losses. Yet suspension losses are often
> > larger than hysteresis losses, and are greatly influenced by tire
> > characteristics.
>
> > Again, if this thinking were extended just a little, it would lead
> > one to abandon pneumatic tires. That indicates it's mistaken.
> > Suspension losses ought to be accounted for somewhere. A "rolling
> > resistance" test seems like the logical place to do so, even if it
> > calls for some redefinition.
>
> introduce other problems. For example, redefining "rolling resistance"
> to be "hysteresis losses + suspension losses," which is I think what JS
> and some others try to get at when discussing the "real world"
> application of rolling resistance.
>
> That the road surface makes a difference is evident on most bike rides.
> Riding on wood versus smooth concrete versus fine-grained asphalt versus
> coarse asphalt, etc., are noticeably different in the amount of power
> input to the pedals is required to maintain speed.
>
> --
> That'll put marzipan in your pie plate, Bingo.
Precisely. What's the point of a RR measurement if we can't relate it
to the real world?
I see some brave folks are working on the issue, so I'll wait
patiently.
Regards,
James.
Michael Press
Tim McNamara <tim...@bitstream.net> wrote:
> In article
> <77c1db81-fac0-4c98...@k39g2000yqd.googlegroups.com>,
> Frank Krygowski <frkr...@gmail.com> wrote:
>
> > On Jul 5, 1:42 am, Tim McNamara <tim...@bitstream.net> wrote:
> > >
> > >
> > > Rolling resistance is a property of the tire. The smooth drum test
> > > is the best tool we have for isolating and quantifying that
> > > property. Rolling resistance as a property of the tire won't
> > > change significantly from one surface to the next.
> > >
> > > The losses on smoother versus rougher surfaces are suspension
> > > losses; these are much harder to quantify. The occasionally
> > > maligned Jan Heine has made some efforts in this direction using a
> > > Tune Power Tap hub and has published those in his magazine, Bicycle
> > > Quarterly.
> >
> > Yes, for bicycles, rolling resistance is usually defined as a
> > property of the tire - i.e., most people seem to limit the definition
> > to the resistance due to tire hysteresis.
>
> Yes, the coefficient of rolling resistance, Crr.
>
> > But most people who define rolling resistance that way seem to give
> > no mention to suspension losses. Yet suspension losses are often
> > larger than hysteresis losses, and are greatly influenced by tire
> > characteristics.
> >
> > Again, if this thinking were extended just a little, it would lead
> > one to abandon pneumatic tires. That indicates it's mistaken.
> > Suspension losses ought to be accounted for somewhere. A "rolling
> > resistance" test seems like the logical place to do so, even if it
> > calls for some redefinition.
>
> Easily done although perhaps a nonstandard use of terminology, which can
> introduce other problems. For example, redefining "rolling resistance"
> to be "hysteresis losses + suspension losses," which is I think what JS
> and some others try to get at when discussing the "real world"
> application of rolling resistance.
>
> That the road surface makes a difference is evident on most bike rides.
> Riding on wood versus smooth concrete versus fine-grained asphalt versus
> coarse asphalt, etc., are noticeably different in the amount of power
> input to the pedals is required to maintain speed.
I disagree.
Leave rolling resistance as the power dissipated in the tire.
Define other power losses and measure them.
--
Michael Press
Jobst Brandt
> Precisely. What's the point of a RR measurement if we can't relate
> it to the real world?
The rolling resistance of interest is the internal energy used by the
tire when rolling under load. That energy is lost in the flex of the
casing, tread, and inner tube (or internal pneumatic barrier) of a
tire under a test load and inflation pressure. You have seen that
information in the IRC bicycle tire tests, performed on smooth steel
drums.
http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html
What you seem to be calling "the real world" is known in the tire
industry as tread squirm from surface roughness. That effect is
uniform for most rubber tires unless they have large tread patterns
with voids into which rubber would deform in coarse paving. That is
not the intent of measuring rolling resistance. The less road
contact, the greater the tread squirm.
> I see some brave folks are working on the issue, so I'll wait
> patiently.
Don't go to sleep. I can't imagine what tire manufacturer is "working
on it" and why.
Jobst Brandt
James
> In article <timmcn-DD508C.14080805072...@news-1.mpls.iphouse.net>,> > <77c1db81-fac0-4c98-becf-0c791dd0a...@k39g2000yqd.googlegroups.com>,
Alert - wild uncensored thought approaching...
What if as you ride over a bump, the momentary increase in air
pressure inside the tire causes some heat to be generated in the air
(work done to compress the air), and the process isn't adiabatic? I
guess the same heat energy is gained as the fluid expands again, so
maybe the net result is zip, or has some of that energy gone into
slowing the bicycle?
Could it be that the rider experiences impulses of force in reverse as
tire hits an imperfection in the road surface going forward?
When the bicycle wheel hits a lump, it translates some forward motion
into vertical motion. A change in velocity. There is no net gain in
altitude as the bicycle falls back to earth. With all spring and no
(little) damping, the wheel can't track the other side of the lump, so
it doesn't receive a relative push forward going down the other side
of the lump. Where did the energy go? Absorbed by the riders body?
(I did warn you that it was a wild thought ;-)
BTW, I agree. The concept of RR should be kept separate. It seems
well defined and tested.
JS.
Frank Krygowski
> James Steward wrote:
> > Precisely. What's the point of a RR measurement if we can't relate
> > it to the real world?
>
> The rolling resistance of interest is the internal energy used by the
> tire when rolling under load.
I think for most cyclists, the resistance of interest is the total
resistance to their forward progress. Our current semantic problem is
whether the term "rolling resistance" should be defined to include
_only_ that energy loss within the tire.
Personally, I think that strict definition has caused some confusion.
Still, I'd be willing to accept it provided suspension losses are
given suitable emphasis. And it seems to me that emphasis on
suspension losses should be greater than that given to the internal
losses measured on a smooth steel drum.
> That energy is lost in the flex of the
> casing, tread, and inner tube (or internal pneumatic barrier) of a
> tire under a test load and inflation pressure. You have seen that
> information in the IRC bicycle tire tests, performed on smooth steel
> drums.
>
> http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html
But we don't do much of our riding on smooth steel drums.
> What you seem to be calling "the real world" is known in the tire
> industry as tread squirm from surface roughness.
That's not what I'm referring to. I'm talking about suspension
losses, the energy consumed by tossing the bike+rider up and down as
they pass over rough surfaces.
We use pneumatic tires primarily to reduce those losses. Yet steel
drum tests don't measure that reduction capacity. It seems to be a
case of using the easiest test, even though it doesn't measure what's
most important.
- Frank Krygowski
James
> James Steward wrote:
> > Precisely. What's the point of a RR measurement if we can't relate
> > it to the real world?
>
> The rolling resistance of interest is the internal energy used by the
> tire when rolling under load. That energy is lost in the flex of the
> casing, tread, and inner tube (or internal pneumatic barrier) of a
> tire under a test load and inflation pressure. You have seen that
> information in the IRC bicycle tire tests, performed on smooth steel
> drums.
>
> http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html
Yes, I've read the article. Thanks. I'm not disputing the test
results. What I am interested in is how we can apply them alone to
the real world, when the real world is not a smooth steel surface, and
it's not a dead weight sitting on the tire either.
Maybe it is all rider perception, I don't know, but cyclists generally
agree than a nice smooth surface (like on a wood or concrete
velodrome) _feels_ faster than sharp pointed 1/2" aggregate (or what
some here call crocodile bite #2).
> What you seem to be calling "the real world" is known in the tire
> industry as tread squirm from surface roughness. That effect is
> uniform for most rubber tires unless they have large tread patterns
> with voids into which rubber would deform in coarse paving. That is
> not the intent of measuring rolling resistance. The less road
> contact, the greater the tread squirm.
Real world briefly described above. As most bicycle tires I'm
interested in are devoid of tread pattern, can we ignore squirm?
BTW, the tire must do an awful lot of squirming over some of the
country roads I've toured on around here ;-)
> > I see some brave folks are working on the issue, so I'll wait
> > patiently.
>
> Don't go to sleep. I can't imagine what tire manufacturer is "working
> on it" and why.
Bicycle Quarterly I believe was doing some investigation. Don't know
if it continuing.
Regards,
James.
Jobst Brandt
> Alert - wild uncensored thought approaching...
> What if as you ride over a bump, the momentary increase in air
> pressure inside the tire causes some heat to be generated in the air
> (work done to compress the air), and the process isn't adiabatic? I
> guess the same heat energy is gained as the fluid expands again, so
> maybe the net result is zip, or has some of that energy gone into
> slowing the bicycle?
You are revealing that you don't understand how pneumatic tires work.
Hitting a bump does not increase tire inflation pressure, the internal
volume remaining essentially unchanged. If you doubt it, put a tire
gauge on a soft tire and jump on the bicycle to observe pressure.
> Could it be that the rider experiences impulses of force in reverse
> as tire hits an imperfection in the road surface going forward?
Stop the vague conjecture, you don't understand how pneumatic tires
work and your model is fictitious.
> When the bicycle wheel hits a lump, it translates some forward
> motion into vertical motion. A change in velocity.
> There is no net gain in altitude as the bicycle falls back to earth.
> With all spring and no (little) damping, the wheel can't track the
> other side of the lump, so it doesn't receive a relative push
> forward going down the other side of the lump. Where did the energy
> go? Absorbed by the riders body?
You'd better describe the model you perceive to support that claim.
Any speed loss arises from climbing a small hill and if you ride much
you will recall that small smooth rises in the road cause no loss of
speed or demand energy. You need to investigate "the ramp and the
ball" mechanisms.
Two identical balls roll down a ramp to a flat plane side-by-side
except that one travels across an area with a smooth, rounded,
V-shaped dip in it. The question is "Which one gets to the finish
line first?" Just look at their average speed and you'll see the one
that goes through the dip is slightly faster. This experiment can be
reversed with a bump in one lane. The final speed for both balls is
the same in both forms.
> (I did warn you that it was a wild thought ;-)
Excuses, excuses!
> BTW, I agree. The concept of RR should be kept separate. It seems
> well defined and tested.
Jobst Brandt
Jobst Brandt
>>> Precisely. What's the point of a RR measurement if we can't
>>> relate it to the real world?
>> The rolling resistance of interest is the internal energy used by
>> the tire when rolling under load.
> I think for most cyclists, the resistance of interest is the total
> resistance to their forward progress. Our current semantic problem
> is whether the term "rolling resistance" should be defined to
> include _only_ that energy loss within the tire.
We aren't trying to define what energy a rider is exerting but rather
which tire has overall better or worse RR. No one has yet defined the
road on which the rider will travel and no one has stated what
tread-squirm on various pavements will be, but RR is well defined for
tire losses are various pressures.
> Personally, I think that strict definition has caused some
> confusion. Still, I'd be willing to accept it provided suspension
> losses are given suitable emphasis. And it seems to me that
> emphasis on suspension losses should be greater than that given to
> the internal losses measured on a smooth steel drum.
>> That energy is lost in the flex of the casing, tread, and inner
>> tube (or internal pneumatic barrier) of a tire under a test load
>> and inflation pressure. You have seen that information in the IRC
>> bicycle tire tests, performed on smooth steel drums.
http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html
> But we don't do much of our riding on smooth steel drums.
Nice smart Alec comment, dodging the issue.
>> What you seem to be calling "the real world" is known in the tire
>> industry as tread squirm from surface roughness.
> That's not what I'm referring to. I'm talking about suspension
> losses, the energy consumed by tossing the bike+rider up and down as
> they pass over rough surfaces.
> We use pneumatic tires primarily to reduce those losses. Yet steel
> drum tests don't measure that reduction capacity. It seems to be a
> case of using the easiest test, even though it doesn't measure
> what's most important.
What sort of bicycle do you propose the tire manufacturers should use
with what sort of suspension and shock absorbers? This sounds like a
can of worms for testing to me and not comparable. You'll notice the
tires IRC tested were road tires with no suspension or bicycle
involved.
Jobst Brandt
James
Fair enough. What does "essentially unchanged" mean?
> > Could it be that the rider experiences impulses of force in reverse
> > as tire hits an imperfection in the road surface going forward?
>
> Stop the vague conjecture, you don't understand how pneumatic tires
> work and your model is fictitious.
Is it? How? Taking your balls rolling along a plate test, (are they
steel ball bearings?) what happens if one is sent over a patch of
rough sand paper, while the other is left to roll over a smooth plate?
> > When the bicycle wheel hits a lump, it translates some forward
> > motion into vertical motion. A change in velocity.
> > There is no net gain in altitude as the bicycle falls back to earth.
> > With all spring and no (little) damping, the wheel can't track the
> > other side of the lump, so it doesn't receive a relative push
> > forward going down the other side of the lump. Where did the energy
> > go? Absorbed by the riders body?
>
> You'd better describe the model you perceive to support that claim.
I thought I did. It certainly feels like I need to push harder if I
ride on one of our AudioTactile line markings. http://tinyurl.com/33emb7w
Damn stuff nearly shakes you to pieces at 40km/h.
> Any speed loss arises from climbing a small hill and if you ride much
> you will recall that small smooth rises in the road cause no loss of
> speed or demand energy. You need to investigate "the ramp and the
> ball" mechanisms.
> Two identical balls roll down a ramp to a flat plane side-by-side
> except that one travels across an area with a smooth, rounded,
> V-shaped dip in it. The question is "Which one gets to the finish
> line first?" Just look at their average speed and you'll see the one
> that goes through the dip is slightly faster. This experiment can be
> reversed with a bump in one lane. The final speed for both balls is
> the same in both forms.
I don't see how this relates to the situation I described. My idea is
that the tire becomes momentarily air born traveling over very rough
surfaces when it is inflated to rock hard.
Do you personally not feel that riding a smooth surface is easier than
a rough one? What is your explanation of other riders perception?
Regards,
James.
Tim McNamara
<f65e6934-a7ff-4627...@q21g2000prm.googlegroups.com>,
James <james.e...@gmail.com> wrote:
Some of the energy is lost in the transition from forward motion to
upward motion (compression of the tire, flex in the fork and steerer,
etc.). Most of it is lost to hysteresis in the rider's tissues. Watch
how much somebody jiggles over a washboard surface.
Frank Krygowski
> Frank Krygowski wrote:
> > I think for most cyclists, the resistance of interest is the total
> > resistance to their forward progress. Our current semantic problem
> > is whether the term "rolling resistance" should be defined to
> > include _only_ that energy loss within the tire.
>
> We aren't trying to define what energy a rider is exerting but rather
> which tire has overall better or worse RR.
?? Sorry, that makes no sense - at least, for the typical cyclist.
Almost no cyclists are interested specifically in the energy loss
within their tires. Instead, they are interested in their ease of
progress. Those desiring an easier ride probably care little whether
it comes from reducing hysteresis losses or suspension losses (or, for
that matter, other losses). If they were told "This tire will make it
ten percent easier for you to pedal, but its internal hysteresis
losses are actually worse than what you're now riding," well, they
wouldn't even hear the second half of the sentence! Why would they
care?
> No one has yet defined the
> road on which the rider will travel and no one has stated what
> tread-squirm on various pavements will be, but RR is well defined for
> tire losses are various pressures.
Right. There's work to be done. Only the easier (and less important)
part of the problem has been solved.
> You have seen that information in the IRC
> >> bicycle tire tests, performed on smooth steel drums.
>
> http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html
>
> > But we don't do much of our riding on smooth steel drums.
>
> Nice smart Alec comment, dodging the issue.
Calm down, Jobst. You know I respect your technical knowledge. That
remark wasn't intended to be disrespectful nor dodging. (And to use
your characteristic style, I might ask "Who is this Alec to whom you
refer?")
> > I'm talking about suspension
> > losses, the energy consumed by tossing the bike+rider up and down as
> > they pass over rough surfaces.
> > We use pneumatic tires primarily to reduce those losses. Yet steel
> > drum tests don't measure that reduction capacity. It seems to be a
> > case of using the easiest test, even though it doesn't measure
> > what's most important.
>
> What sort of bicycle do you propose the tire manufacturers should use
> with what sort of suspension and shock absorbers? This sounds like a
> can of worms for testing to me and not comparable. You'll notice the
> tires IRC tested were road tires with no suspension or bicycle
> involved.
Yes, I notice that long ago. That's why I pointed out that the IRC
tests would probably measure the tire of a pre-pneumatic safety bike
as being the optimum. But experience has taught us that it's not.
That indicates the test is missing much.
And yes, it is a "can of worms," i.e. a non-trivial problem. I
suspect we'd have to replicate the energy-absorbing characteristics of
a typical rider's body. And since I'm sure the degree of road
roughness is important, we'd have to find a way to characterize that.
Probably the best we could do would be to rate tires for, say, an
average rider on three different road roughnesses.
But I think much of the work (of describing the body and the road)
has already been done. We're not the only ones interested in those
matters. What remains is to dig out the knowledge, design a more
realistic test rig based on that knowledge, and test some tires.
- Frank Krygowski
James
Thank you. My point exactly.
Best Regards,
James.
Tim McNamara
Jobst Brandt <jbr...@sonic.net> wrote:
The issue at discussion has gone beyond hysteresis losses in the tire
and tube, and is about the total system of a cyclist riding on a road or
trail, not just a flexing tire. Where is energy lost? Can that energy
loss be prevented?
Hysteresis losses within the tire are one source of energy loss.
Suspension losses from the rider and bicycle bouncing over the surface
are another. There may be further sources of loss. One measurement
method maybe power meters like the Sram crank or Tune hub. At least one
attempt has been made comparing different tires and forks on smooth and
rough roads.
From the May thread on a similar discussion:
Summary: The tests were done using a Tune Power tap and riding the bike
with different tires at a constant speed of 19 mph out and back on the
same stretch of road. Smooth pavement was just what it says; rough
pavement was riding on the rumble strip.
Smooth pavement:
Worst tire (Bontrager Racelite Hardcase 700 x 27 @ 95 psi) = 232 W
Best tire (Panaracer Pasela 700 x 35 @ 50 psi) = 198 W
Difference of 34 W.
Rough pavement:
Worst tire (Bontrager Racelite Hardcase 700 x 27 @ 95 psi) = 479 W
Best tire (Panaracer Pasela 700 x 35 @ 50 psi) = 313 W
So the difference was 160 W on rough pavement.
(S)uspension losses as the bike bounces over the surface. These losses
are probably mainly due to hysteresis in the rider's body; hysteresis
in tissue is also a factor in losses in normal physical activity, hence
why compression clothing shows a gain in performance.
Heine's testing also compared forks using the same wheels on the same
bike.
Smooth pavement:
Worst fork: Trek unicrown with large diameter legs: 237 W
Best fork: RockShox Ruby: 203 W
Difference of 34W.
Rough pavement:
Worst fork: Trek hybrid unicrown with large diameter legs: 459 W
Best fork: (tie) Rock Shox Ruby @ 428 W and Alex Singer thin steel @
426 W
Difference of 31W.
Interesting that the suspension fork provided about the same reduction
in energy cost to maintain a constant speed, ~ 30W, on both smooth and
rough pavement. The differences between worst and best tires was much
greater between smooth and rough pavement. Stiction in the suspension
fork mechanism might explain this.
Jobst Brandt
Down in the measurement noise... the variability in a tire is larger
than what you want to measure.
>>> Could it be that the rider experiences impulses of force in reverse
>>> as tire hits an imperfection in the road surface going forward?
Try some trigonometry on this and how large riding on a standard well
maintained road surface affects rate of climb on a level section.
>> Stop the vague conjecture, you don't understand how pneumatic tires
>> work and your model is fictitious.
> Is it? How? Taking your balls rolling along a plate test, (are they
> steel ball bearings?) what happens if one is sent over a patch of
> rough sand paper, while the other is left to roll over a smooth plate?
>>> When the bicycle wheel hits a lump, it translates some forward
>>> motion into vertical motion. A change in velocity.
>>> There is no net gain in altitude as the bicycle falls back to earth.
>>> With all spring and no (little) damping, the wheel can't track the
>>> other side of the lump, so it doesn't receive a relative push
>>> forward going down the other side of the lump. Where did the energy
>>> go? Absorbed by the riders body?
>> You'd better describe the model you perceive to support that claim.
> I thought I did. It certainly feels like I need to push harder if I
> ride on one of our Audio-Tactile line markings.
> Damn stuff nearly shakes you to pieces at 40km/h.
So what does this have to do with rolling resistance. You are trying
hard to throw a monkey wrench into a well e stablished parameter of
pneumatic tires.
>> Any speed loss arises from climbing a small hill and if you ride
>> much you will recall that small smooth rises in the road cause no
>> loss of speed or demand energy. You need to investigate "the ramp
>> and the ball" mechanisms. Two identical balls roll down a ramp to
>> a flat plane side-by-side except that one travels across an area
>> with a smooth, rounded, V-shaped dip in it. The question is "Which
>> one gets to the finish line first?" Just look at their average
>> speed and you'll see the one that goes through the dip is slightly
>> faster. This experiment can be reversed with a bump in one
>> lane. The final speed for both balls is the same in both forms.
> I don't see how this relates to the situation I described. My idea
> is that the tire becomes momentarily air born traveling over very
> rough surfaces when it is inflated to rock hard.
OH! How very? Very is a term not found in science, being mainly a
word for people grasping at straws in definitions.
The next test demanded by you might be riding down stairs. Get with
it and understand what the losses in tires are.
> Do you personally not feel that riding a smooth surface is easier
> than a rough one? What is your explanation of other riders
> perception?
That's not the question at hand but rather what is the measure of
rolling resistance of similar tires as the chart offered shows.
Jobst Brandt
James
> >>> as tire hits an imperfection in the road surface going forward?
>
> Try some trigonometry on this and how large riding on a standard well
> maintained road surface affects rate of climb on a level section.
I can't make sense of that sentence, sorry. Can you please rephrase
it?
We are not discussing climbing hills, we're talking about how tire
pressure affect "perceived" rolling resistance over various types of
commonly found road surface - i.e. "the real world" as I put it.
> >> You'd better describe the model you perceive to support that claim.
> > I thought I did. It certainly feels like I need to push harder if I
> > ride on one of our Audio-Tactile line markings.
>
> http://tinyurl.com/33emb7w
>
> > Damn stuff nearly shakes you to pieces at 40km/h.
>
> So what does this have to do with rolling resistance. You are trying
> hard to throw a monkey wrench into a well e stablished parameter of
> pneumatic tires.
No I'm not. I am saying there's more to the "well established
parameter of pneumatic tires" than just the tire as perceived by
riders.
Tim perhaps describes the situation better than I. http://tinyurl.com/26hs3gk
Thanks Tim. I wasn't aware of that thread.
> > I don't see how this relates to the situation I described. My idea
> > is that the tire becomes momentarily air born traveling over very
> > rough surfaces when it is inflated to rock hard.
>
> OH! How very? Very is a term not found in science, being mainly a
> word for people grasping at straws in definitions.
I did describe some very rough roads as "sharp pointed 1/2" aggregate
(or what
some here call crocodile bite #2)."
The AudioTactile line marking is very very rough on a road bike with
hard (120psi 23c) tires. Rock hard being even harder. Is that enough
unscientific terms for you, Jobst?
> The next test demanded by you might be riding down stairs. Get with
> it and understand what the losses in tires are.
Which is not what we are discussing any more. The subject has morphed
into tire pressure and _perceived_ rolling resistance, for want of a
better term, over non ideal, real world surfaces - i.e. not a steel
drum.
As I have said, I do not dispute the well established tire related
losses as described by the graphs you point to. If riders feel that a
rough road makes it harder to ride at the same speed than on a smooth
surface, their energy must be going somewhere. Obviously not into the
tire, but the inflation pressure may contribute to the amount of
energy wasted by the entire system. No?
Regards,
James.
James
> The issue at discussion has gone beyond hysteresis losses in the tire
> and tube, and is about the total system of a cyclist riding on a road or
> trail, not just a flexing tire. Where is energy lost? Can that energy
> loss be prevented?
Thanks Tim. Could someone please tell Jobst?
Regards,
James.
MikeWhy
The biggest and simplest reason is because what you're calling suspension
losses is a separate term, likely several terms. It relates to empirical
measures of road roughness, both amplitude and frequency, while Crr relates
only to road speed.
James
Actually it's always been about tire pressure and perceived rolling
resistance - that is not just Crr.
JS.
Michael Press
Phil W Lee <ph...@lee-family.me.uk> wrote:
> Michael Press <rub...@pacbell.net> considered Mon, 05 Jul 2010
> Suspension losses are far better dissipated in the tyre than by
> bouncing the whole bike and rider around.
> And probably far easier to measure there, and more relevantly.
>
> >Define other power losses and measure them.
>
> You might as well try to separate the losses in the tyre carcass from
> those due to tread squirm and from those absorbed in the air inside.
>
> It's all lost in the tyre, so that is the place to measure it.
That is not what others say about suspension losses.
--
Michael Press
James
> Michael Press <rub...@pacbell.net> considered Mon, 05 Jul 2010
> 17:45:01 -0700 the perfect time to write:
>
> >Leave rolling resistance as the power dissipated in the tire.
>
> bouncing the whole bike and rider around.
> And probably far easier to measure there, and more relevantly.
>
>
> those due to tread squirm and from those absorbed in the air inside.
>
> It's all lost in the tyre, so that is the place to measure it.
What is lost in the tire? As Jobst says, only the flexure of the
rubber compound contributes to losses in the tire (and a little in
tread squirm). It doesn't absorb suspension losses, but it does
reduce the suspension vibration input by not transmitting the
vibrations through the frame to the rider.
How does the air inside absorb energy? Jobst says it doesn't. I have
no reason to doubt this claim.
The suspension losses is where it's at, but I can't see much of them
being dissipated by the tire. More likely by riders body. I imagine
most bike parts (frame, forks, rims, spokes) are fairly good springs -
i.e. don't absorb much vibration energy. The human body however, it
absorbs most of what comes up from the road. The harder the tires and
the rougher the surface the more energy the human body absorbs.
How much energy? The difference between riding a slick surface and
the surface of interest at the same tire pressure. Tim McNamara
kindly posted some test results http://tinyurl.com/3a8g9ug .
Regards,
James.
thirty-six
While I agree that the smooth roller test is inadequate as an true
indicator of road resistance, I think much can be gained by testing
with a simple load at low speeds over standard surfaces. This would
include the increase in casing and tread losses due to greater
displacement around a 'stony' surface.
>
> But I think much of the work (of describing the body and the road)
> has already been done. We're not the only ones interested in those
> matters. What remains is to dig out the knowledge, design a more
> realistic test rig based on that knowledge, and test some tires.
1.1/8" is the smallest cover a day tourist (of around 11st) would use
over good roads post WWII in Britain. There has not been such an
improvement in roads to use anything narrower even if avoiding the
worst roads. So if the steel drum Rolling resistance figures are to
be used to effect then they should not be compared across the range of
sizes, pick your size according to experience then consider rolling
resistances for this size.
Of course if you select a racing bike, you will only have enough room
for tubular tyres of any great shock absorption. You will then be
unable to experience why 1.1/4 covers and wider are so valued.
thirty-six
> In article <4c32948f$0$1637$742ec...@news.sonic.net>,
Not only is there the loss of energy by being transferred into
vertical motion, that motion is fatiguing on the rider and he will be
able to output a lower energy rate as the day wears on due
specifically to the fatigue induced through the vertical vibrations.
thirty-six
Higher inflation pressures stiffen the tyre walls, so limiting the
suspension available within the tyre, increasing the vertical shock
transmission. Damping of the sidewalls with thick rubber/latex
reduces the amount of buzz which can be found from some surfaces, but
generally feels that an unacceptable amount of drag is incurred when
using smoother surfaces.
Tim McNamara
<a8b28caf-e9dd-446e...@7g2000prh.googlegroups.com>,
James <james.e...@gmail.com> wrote:
> On Jul 6, 1:30 pm, Phil W Lee <p...@lee-family.me.uk> wrote:
> > Michael Press <rub...@pacbell.net> considered Mon, 05 Jul 2010
> > 17:45:01 -0700 the perfect time to write:
> >
> > >I disagree. Leave rolling resistance as the power dissipated in
> > >the tire.
> >
> > Suspension losses are far better dissipated in the tyre than by
> > bouncing the whole bike and rider around. And probably far easier
> > to measure there, and more relevantly.
> >
> > >Define other power losses and measure them.
> >
> > You might as well try to separate the losses in the tyre carcass
> > from those due to tread squirm and from those absorbed in the air
> > inside.
> >
> > It's all lost in the tyre, so that is the place to measure it.
>
> What is lost in the tire? As Jobst says, only the flexure of the
> rubber compound contributes to losses in the tire (and a little in
> tread squirm). It doesn't absorb suspension losses, but it does
> reduce the suspension vibration input by not transmitting the
> vibrations through the frame to the rider.
Which reduces suspension losses. Suspension allows the wheel to move up
and down independently of the main mass of the vehicle; the energy cost
of moving the smaller mass is much lower than that of moving the entire
vehicle. In the case of pneumatic tires, the tire deforms over the
surface of the road; with small irregularities the rider may barely know
they are there (e.g., "road buzz"); as the irregularities get larger,
the ability of the tire to deform enough becomes increasingly limited.
Tire pressure, the flexibility of the tire and the minor diameter of the
tire are all limiting factors. Wide soft tires can accommodate larger
irregularities without transmitting the jolt to the bike and rider than
skinny hard tires.
> How does the air inside absorb energy? Jobst says it doesn't. I
> have no reason to doubt this claim.
I think that Jobst is right about that because the air doesn't
significantly compress within the tire due to the deformation. The tire
is a column of air with a constant length and diameter rolled into a
hoop. At the contact patch there is compression of opposing sides of
the tire (between the rim and the ground) but the tire accommodates this
by bulging out to the sides.
> The suspension losses is where it's at, but I can't see much of them
> being dissipated by the tire. More likely by riders body. I imagine
> most bike parts (frame, forks, rims, spokes) are fairly good springs
> - i.e. don't absorb much vibration energy. The human body however,
> it absorbs most of what comes up from the road. The harder the tires
> and the rougher the surface the more energy the human body absorbs.
>
> How much energy? The difference between riding a slick surface and
> the surface of interest at the same tire pressure. Tim McNamara
> kindly posted some test results http://tinyurl.com/3a8g9ug .
Hysteresis losses in the tire- the strict interpretation of rolling
resistance- are considerable. IIRC, according to the various data
available, at 20 mph it is still about 25-30% of the energy cost of
propelling a bicycle.
Tim McNamara
"MikeWhy" <boat042...@yahoo.com> wrote:
Crr is independent of road speed.
Frank Krygowski
> > ride on one of our Audio-Tactile line markings.
>
> http://tinyurl.com/33emb7w
>
> > Damn stuff nearly shakes you to pieces at 40km/h.
>
> So what does this have to do with rolling resistance. You are trying
> hard to throw a monkey wrench into a well e stablished parameter of
> pneumatic tires.
The point is, the "well e stablished [sic] parameter" is only one
parameter, and probably not the most important one for use of an
actual bicycle by an actual rider on an actual road.
What many of us are saying is that the most efficient tire on a smooth
steel drum is not necessarily the fastest tire on the road. Do you
really believe the opposite - that efficiency on smooth steel
correlates perfectly with efficiency on, say, coarse cracked asphalt?
> > My idea
> > is that the tire becomes momentarily air born traveling over very
> > rough surfaces when it is inflated to rock hard.
>
> OH! How very? Very is a term not found in science, being mainly a
> word for people grasping at straws in definitions.
Hmmm. Do school-marm digressions into textbook English really help
communication? Is that Alec speaking?
Let's stick to the point. Do you, Jobst, _really_ think the best
steel drum tire is always the best rough road tire?
- Frank Krygowski
Frank Krygowski
>
> It's all lost in the tyre, so that is the place to measure it.
I think it's clear it's not all lost in the tire.
Let's take the extreme case. We'll run steel wheels on a steel
surface, so there's almost no hysteresis; but we'll make the rail
"very" rough (that was for Jobst) such that the steel-wheeled bike and
rider rumbles harshly over the surface and the rider feels that
harshness.
Would you not expect much more resistance, compared to an appropriate
pneumatic tire? I certainly would! Yet in the steel-on-steel case,
there would be nothing lost in the nonexistent tire. There'd be
almost nothing lost in the steel wheel, either.
(But, BTW, the steel wheel would beat the pneumatic tire in the smooth
drum test!)
- Frank Krygowski
Frank Krygowski
> James wrote:
> >
> > Precisely. What's the point of a RR measurement if we can't relate it
> > to the real world?
>
> The biggest and simplest reason is because what you're calling suspension
> losses is a separate term, likely several terms. It relates to empirical
> measures of road roughness, both amplitude and frequency, while Crr relates
> only to road speed.
I think this is fine, if we all accept that definition of Crr.
But again, this means there is a much more important factor that
almost nobody is measuring. Yes, it's harder to measure - but that
doesn't mean we should pretend it doesn't matter!
- Frank Krygowski
thirty-six
> (But, BTW, the steel wheel would beat the pneumatic tire in the smooth
> drum test!)
and oiled it. :-)
Lou Holtman
What important factor is that Frank except tire pressure?
Lou
carl...@comcast.net
Dear Lou,
Width? Shape? Tire design? Inner tube?
Practical tire drag consists of:
1) Pure rolling resistance, what Jobst measured on the steel drum and
which Frank reminds us will mistakenly crown a steel tire as king.
Pure steel-drum Crr depends on tire width, pressure, and design
(thread count, tread thickness, and so on).
Look at Jobst's graph, and you'll see that the Avocet 30 28c (lowest
purple line) had less rolling resistance than _all_ other tires at the
same pressure, including the other 28mm tires:
http://www.terrymorse.com/bike/imgs/rolres.gif
In fact, the fat Avocet 30 28c tire had lower rolling resistance at 6
kg/cm^2 pressure than seven other tires at 9 kg/cm^2, 50% higher. So
pressure alone tells us darned little.
2) Tire width and pressure affect suspension loses.
The fatter Avocet 30 28c would probably do well here, too. Testing
shows that on real roads, bikes pedaled by human beings roll faster on
tires with pressures considerably lower than 120 psi. The riders
jiggle less and don't get so tired. Running down rumble strips
exaggerates the effect, but it's real.
3) Tire shape and width affect aerodynamics.
The smooth Avocet 20 28c had no knobs, but no racer would be caught
dead trying to push a pair of 28mm wide tires down the road.
Knobs are hideous, aerodynamically, and a little arithmetic on the
frontal area will suggest why racers love narrow tires. A 700c tire is
about 675 mm tall, and each tire has a front and a back, so a rough
approximation of tire-frontal area is:
28 mm x 675 mm x 4 = 75,600 mm^2
23 mm x 675 mm x 4 = 62,100 mm^2
A 5 mm narrower tire reduces frontal area roughly 3500 mm^2, a square
about 2.3 inches wide. A racer worried about grams isn't going to
stick a 2.3-inch square out into the wind.
4) Inner-tube, which takes us back to pure Crr. The inner-tube is
effectively part of the tire design, flexing with it at the contact
patch.
Thinner inner-tubes have measurably lower Crr, and latex does
measurably better than butyl. See Al Morrison's test sections for
latex versus butyl and Misc Inner tube tests near the end of the PDF:
http://www.biketechreview.com/tires_old/images/AFM_tire_testing_rev9.pdf
Cheers,
Carl Fogel
bfd
sidwall Avocet Fasgrip "Road" 700x28 tire used in this test was
mislabeled and actually measured between 24-26mm wide. It is the same
tires used by Jobst in this photo:
http://www.sheldonbrown.com/brandt/images/tiretest.jpg
Good Luck!
carl...@comcast.net
Dear BFD,
Interesting--and odd if a reasonably inflated tire had a 2mm variance.
Cheers,
Carl Fogel
bfd
to compete with Specialized and other tire mfrs as to who had the
"lightest" tires on the market. By listing a *true *700x25 tire as a
700x28, a company could advertise that it had the "lightest" tire in
that size! I recall Avocet's 700x25 were actually measured at 21-22mm
and its 700x20 tire was a 700x18.
Decades later, Avocet had its Fasgrip "Road" tire made in Korea
instead of Japan as IRC moved their plant to reduce cost, and this all
black tire was accurately labeled at 700x25. Of course, the Korean
plant burned down and Avocet is basically out of business, although
they still have a website and someone does answer the phone! Good Luck!
thirty-six
> Look at Jobst's graph, and you'll see that the Avocet 30 28c (lowest
> purple line) had less rolling resistance than _all_ other tires at the
> same pressure, including the other 28mm tires:
> http://www.terrymorse.com/bike/imgs/rolres.gif
I'd rather compare 'equal' tyres by knowing their bead to bead
dimension than by advertised size. Was not Avocet one of the leaders
for incorrect tyre designation?
>
> In fact,
Oh, here we go.
> 2) Tire width and pressure affect suspension loses.
>
> The fatter Avocet 30 28c would probably do well here, too.
Why, what is the bead to bead dimension?
> Testing
> shows that on real roads, bikes pedaled by human beings roll faster on
> tires with pressures considerably lower than 120 psi. The riders
> jiggle less and don't get so tired. Running down rumble strips
> exaggerates the effect, but it's real.
Good place to set spoke tension and tyre pressure for the minimum
vibration.
> 3) Tire shape and width affect aerodynamics.
A round front is perfectly acceptable. Track rims had sloped sides,
probably helping with aerodynamics as much as an aero road rim of
today. The rim top is also rounded of a smaller section than the tyre
when coupled with sloping sides.
>
> The smooth Avocet 20 28c had no knobs, but no racer would be caught
> dead trying to push a pair of 28mm wide tires down the road.
28mm in a tubular is the standard for a Roubaix tyre, 28mm is also
used in tubulars for 'cross bikes, the lower average speeds make tyres
up to the imposed limit more desirous over rougher courses. 28mm in a
tubular would also be the likely choice for racing tandems. Wired-on
tyres would need to be bigger for the same suspension qualities.
23mm high pressure makes a good front tyre, but only satisfactory for
those of light weight in the rear.
>
> Knobs are hideous, aerodynamically, and a little arithmetic on the
> frontal area will suggest why racers love narrow tires. A 700c tire is
> about 675 mm tall, and each tire has a front and a back, so a rough
> approximation of tire-frontal area is:
>
> 28 mm x 675 mm x 4 = 75,600 mm^2
> 23 mm x 675 mm x 4 = 62,100 mm^2
>
> A 5 mm narrower tire reduces frontal area roughly 3500 mm^2, a square
> about 2.3 inches wide. A racer worried about grams isn't going to
> stick a 2.3-inch square out into the wind.
Unless he can see himself actually being faster on course with fatter
tyres.
>
> 4) Inner-tube, which takes us back to pure Crr. The inner-tube is
> effectively part of the tire design, flexing with it at the contact
> patch.
>
> Thinner inner-tubes have measurably lower Crr, and latex does
> measurably better than butyl. See Al Morrison's test sections for
> latex versus butyl and Misc Inner tube tests near the end of the PDF:
>
> http://www.biketechreview.com/tires_old/images/AFM_tire_testing_rev9.pdf
>
Not looked, as yet, but I found that there was certainly a difference
in perceived drag when changing between latex and butyl in the back
tyre, which was probably overloaded, but there did not seem to be a
disadvantage in using a light butyl tube in the front. The reason for
reverting to front butyl was to eliminate shimmy(which it did).
thirty-six
>
> - Show quoted text -
That reminds me, I still have two virtually unused Specialized "25's"
with kevlar band and bead wires. May as well have been running on
iron. Other than being used for club time trials, or light duty
trailer wheels, I can't see any use for them.
What you say about the mislabelling also meant the tyre was harder for
the same pressure as an accurately labelled tyre, so it would do a
better test performance (being more like an iron tyre). There is a
fault of those tests and why they can not be trusted.
Lou Holtman
> On Tue, 06 Jul 2010 18:45:28 +0200, Lou Holtman
> <lhollaatd...@planet.nl> wrote:
>
>> Op 6-7-2010 16:54, Frank Krygowski schreef:
>>> On Jul 6, 12:19 am, "MikeWhy"<boat042-nos...@yahoo.com> wrote:
>>>> James wrote:
>>>>>
>>>>> Precisely. What's the point of a RR measurement if we can't relate it
>>>>> to the real world?
>>>>
>>>> The biggest and simplest reason is because what you're calling suspension
>>>> losses is a separate term, likely several terms. It relates to empirical
>>>> measures of road roughness, both amplitude and frequency, while Crr relates
>>>> only to road speed.
>>>
>>> I think this is fine, if we all accept that definition of Crr.
>>>
>>> But again, this means there is a much more important factor that
>>> almost nobody is measuring. Yes, it's harder to measure - but that
>>> doesn't mean we should pretend it doesn't matter!
>>>
>>> - Frank Krygowski
>>
>>
>> What important factor is that Frank except tire pressure?
>>
>> Lou
>
> Dear Lou,
>
> Width? Shape? Tire design?
Yes I know that but what I meant is when there is a difference between
the measurement on a steel drum and in 'the real world' what causes it?
Inner tube?
Of course, but lets limit ourselves to the tires.
Lou
Frank Krygowski
> Op 6-7-2010 19:28, carlfo...@comcast.net schreef:
>
>
>
> > On Tue, 06 Jul 2010 18:45:28 +0200, Lou Holtman
What I'm saying is that the difference between the real world (AKA
rough asphalt) and the steel drum is that the mass of the bike+rider
gets jostled up and down by the road roughness. This costs
significant power, and rider works harder to overcome it.
I may have described this extreme example before, but here goes:
Many years ago, when I still did a fair amount of mountain biking on
my rigid mountain bike, the finish of a 20 mile ride involved about
half a mile of railroad bed with tracks removed. We were riding on
the ballast, which consisted of course gravel roughly 3" diameter. It
was hideous.
I stopped and deflated my 2" tires to something like 20 psi, low
enough that my riding buddy told me I was sure to get a pinch flat.
But the bike floated over the gravel, and the pedaling was far
easier. (Oddly enough, _he_ got a pinch flat despite his higher
pressures. I didn't. Luck, I suppose.)
It was visually obvious that my tires were flexing far more than
before, so I'm sure the hysteresis losses within the tire were much
greater than when I had higher pressure. Yet the effort to propel the
bike was far less. This effect is due, I'm sure, to greater
suspension losses with the high pressure. The reduction in suspension
loss easily surpassed any increase in hysteresis.
- Frank Krygowski
bfd
variety of sizes - 700x20/21/23, may be even a 25. Back in the day,
early 1980s, that was one of the tire to get as "high performance"
clinchers were just starting to come out!
If you can't find any use for them, perhaps donate them to a shop or
non-profit!
> What you say about the mislabelling also meant the tyre was harder for
> the same pressure as an accurately labelled tyre, so it would do a
> better test performance (being more like an iron tyre). There is a
> fault of those tests and why they can not be trusted
May be, but it still had the lowest rr of all the tires tested that
day! Good Luck!
Jobst Brandt
>>>> Precisely. What's the point of a RR measurement if we can't
>>>> relate it to the real world?
>>> The biggest and simplest reason is because what you're calling
>>> suspension losses is a separate term, likely several terms. It
>>> relates to empirical measures of road roughness, both amplitude
>>> and frequency, while Crr relates only to road speed.
>> I think this is fine, if we all accept that definition of Crr.
>> But again, this means there is a much more important factor that
>> almost nobody is measuring. Yes, it's harder to measure - but that
>> doesn't mean we should pretend it doesn't matter!
> What important factor is that Frank except tire pressure?
Frank did not notice that tire pressure is already part of tire
testing and in the curves plotted by IRC, the observant eye will note
that these are a family of curves that almost exactly replicate each
other if superimposed at the starting point and by use a multiplier
can be matched at the midpoints. That alone should give the test
credibility. I'll admit there were no microphones to record sound
energy dissipated by the various samples. That will most likely be
the next demand for realism that I expect... then comes odor.
Road roughness has nothing to do with the relative losses of various
tires, only that they have negligible tread depth (essentially all
slicks). These standard tests have been done in this format by the
tire industry for many years. I find it ludicrous to claim that
manufacturers have no understanding of tire use reality.
Slicks have practically no road roughness squirm losses because rubber
being incompressible, cannot deform laterally the way knobby or siped
tires do. Lack of lateral squirm is a feature that makes slicks have
low rolling resistance and better traction.
Jobst Brandt
Frank Krygowski
>
> Road roughness has nothing to do with the relative losses of various
So is it your claim that the tire that shows least drag on a steel
drum will definitely show the least drag on a rough, cracked, patched
asphalt road?
- Frank Krygowski
Jobst Brandt
>>>>>>> Precisely. What's the point of a RR measurement if we can't
>>>>>>> relate it to the real world?
>>>>>> The biggest and simplest reason is because what you're calling
>>>>>> suspension losses is a separate term, likely several terms. It
>>>>>> relates to empirical measures of road roughness, both amplitude
>>>>>> and frequency, while Crr relates only to road speed.
>>>>> I think this is fine, if we all accept that definition of Crr.
>>>>> But again, this means there is a much more important factor that
>>>>> almost nobody is measuring. Yes, it's harder to measure - but
>>>>> that doesn't mean we should pretend it doesn't matter!
>>>> What important factor is that Frank except tire pressure?
>>> Width? Shape? Tire design?
>> Yes I know that but what I meant is when there is a difference
>> between the measurement on a steel drum and in 'the real world'
>> what causes it?
>> Inner tube?
>> Of course, but lets limit ourselves to the tires.
Not to worry, all the tests were done with the same inner tubes to not
skew results. All these tires in the test were sent without tubes to
IRC by Avocet.
> What I'm saying is that the difference between the real world (AKA
> rough asphalt) and the steel drum is that the mass of the bike+rider
> gets jostled up and down by the road roughness. This costs
> significant power, and rider works harder to overcome it.
OH! So you want to include the rider with a tire test and no doubt
his bicycle and clothing. This is getting sillier and sillier. What
is the important parameter in the "jostling up and down". How can it
be identified for a tire on the retail shelf other than in words.
> I may have described this extreme example before, but here goes:
> Many years ago, when I still did a fair amount of mountain biking on
> my rigid mountain bike, the finish of a 20 mile ride involved about
> half a mile of railroad bed with tracks removed. We were riding on
> the ballast, which consisted of course gravel roughly 3" diameter.
> It was hideous.
> I stopped and deflated my 2" tires to something like 20 psi, low
> enough that my riding buddy told me I was sure to get a pinch flat.
> But the bike floated over the gravel, and the pedaling was far
> easier. (Oddly enough, _he_ got a pinch flat despite his higher
> pressures. I didn't. Luck, I suppose.)
Let's say YOU floated over the gravel. Just watch Paris Roubaix and
note tire sizes and inflation over the cobbles, even in the TdF.
> It was visually obvious that my tires were flexing far more than
> before, so I'm sure the hysteresis losses within the tire were much
> greater than when I had higher pressure. Yet the effort to propel
> the bike was far less. This effect is due, I'm sure, to greater
> suspension losses with the high pressure. The reduction in
> suspension loss easily surpassed any increase in hysteresis.
Don't let this leak to the tire manufacturers or they'll demand Frank
to become a consultant on tire testing in the new and real world.
Jobst Brandt
Jobst Brandt
>> Road roughness has nothing to do with the relative losses of
>> various tires...
> So is it your claim that the tire that shows least drag on a steel
> drum will definitely show the least drag on a rough, cracked,
> patched asphalt road?
If it is otherwise, you had best explain where the energy is absorbed.
Jobst Brandt
Lou Holtman
Yeah, yeah, but my question is if the tire that performs better at 6 bar
on a steel drum performs worse at a lower pressure on rough asphalt
compared to the tire that performs worse at 6 bar on a steel drum
lowered to the same pressure on the same rough asphalt. I think not and
when I'm have to choose a performance tire I choose the one that has the
lowest Crr on a steel drum.
Lou
Lou Holtman
I think so. Please explain why I'm wrong.
Lou
Frank Krygowski
> Frank Krygowski wrote:
>
>
> > What I'm saying is that the difference between the real world (AKA
> > rough asphalt) and the steel drum is that the mass of the bike+rider
> > gets jostled up and down by the road roughness. This costs
> > significant power, and rider works harder to overcome it.
>
> OH! So you want to include the rider with a tire test and no doubt
> his bicycle and clothing.
Um - For a tire that will be used to support a bike, a rider and his
clothing? Yes, I think that (or its realistic analog) will constitute
an improved test.
> This is getting sillier and sillier. What
> is the important parameter in the "jostling up and down". How can it
> be identified for a tire on the retail shelf other than in words.
The important fact about the jostling is that it does consume energy.
(If you disagree, please state that explicitly so we can discuss.)
The important parameters are probably the amount of energy transmitted
to the mass of the bike+rider through the tires, and perhaps the
energy absorbing characteristics of that mass.
How the parameters can be identified is yet to be determined. But
please don't adopt a know-nothing attitude like "We don't currently
measure that, so it can't be measured."
> Don't let this leak to the tire manufacturers or they'll demand Frank
> to become a consultant on tire testing in the new and real world.
Well, they may notice that others besides Jobst have thought about
these matters, and reached different conclusions. We're still working
out whose conclusions are more accurate. But I don't suppose they'll
completely abandon your consulting business in any case.
- Frank Krygowski
Michael Press
<31075a9c-b25c-44a8...@d16g2000yqb.googlegroups.com>,
Frank Krygowski <frkr...@gmail.com> wrote:
> On Jul 6, 12:19 am, "MikeWhy" <boat042-nos...@yahoo.com> wrote:
> > James wrote:
> > >
> > > Precisely. What's the point of a RR measurement if we can't relate it
> > > to the real world?
> >
> > The biggest and simplest reason is because what you're calling suspension
> > losses is a separate term, likely several terms. It relates to empirical
> > measures of road roughness, both amplitude and frequency, while Crr relates
> > only to road speed.
>
> I think this is fine, if we all accept that definition of Crr.
>
> But again, this means there is a much more important factor that
It has not been measured, so it is not much more important.
> almost nobody is measuring. Yes, it's harder to measure - but that
> doesn't mean we should pretend it doesn't matter!
Simply because many people say big squishy tires are
more efficient over rough pavement does not make it so.
I am holding out for measurements where wind resistance
is not a factor. Not just subtracted on the basis of
estimates of wind resistance, but completely removed
from the laboratory protocol.
--
Michael Press
Frank Krygowski
Such an adversion to the words "Yes" and "No"!
I suspect the energy is absorbed primarily in the damping action of
human tissue. I thought that was obvious.
Look, if you fastened a bike to an electrically driven shaker table by
the bike's dropouts, had a "rider" mount it, and vibrated him and the
bike upward and downward at some reasonable distance and frequency
(say, 5mm amplitude at 100 Hz) would that not require energy to drive
the system?
If the same thing happens to a rider on a rough road, would that not
require the same energy cost?
If other tires - softer, lower pressure ones - reduced the amplitude,
does that not indicate less energy was lost?
- Frank Krygowski
Frank Krygowski
Because if you look at the case of a hard-tired safety wheel & tire,
or a steel wheel, your assumption fails. Both would beat a typical
pneumatic tire during the smooth drum test, but both would be far more
resistive on real pavement. The rougher the pavement, the greater the
discrepancy.
There are good reasons why almost all railroads do not use pneumatic
tires, and why almost all road vehicles do not use steel wheels of
almost infinite hardness. What works on hard, smooth steel doesn't
work on real-world asphalt.
- Frank Krygowski
MikeWhy
"Tim McNamara" <tim...@bitstream.net> wrote in message
news:timmcn-93261D....@news-1.mpls.iphouse.net...
Crr, as in dimensionless coefficient of rolling friction, is used in a power
term involving only road speed as the variable, with mass and gravitational
constant held constant. Power terms always involve velocity.
thirty-six
> On Jul 6, 11:25 am, thirty-six <thirty-...@live.co.uk> wrote:
>
> > That reminds me, I still have two virtually unused Specialized "25's"
> > with kevlar band and bead wires. May as well have been running on
> > iron. Other than being used for club time trials, or light duty
> > trailer wheels, I can't see any use for them.
>
> Are those the old Specialized "Turbo" tires?
That's right, I'd run the kevlar bead with patterned tread in 25s a
few years previously and a few years before that(when they were first
available here). Well a little more weight and a desire to avoid
puncturing a thin treaded tyre did not work in combination.
> I use to run those in a
> variety of sizes - 700x20/21/23, may be even a 25. Back in the day,
> early 1980s, that was one of the tire to get as "high performance"
> clinchers were just starting to come out!
Best claimed rolling resistance in 1984 I think. Got my first in
1985.
>
> If you can't find any use for them, perhaps donate them to a shop or
> non-profit!
If the rubber is still good, I'll possibly try using them as a front
tyre when the time comes. I'll be looking for a super cheap, super
narrow rim to use them with (narrower inside than open4cd).
>
> > What you say about the mislabelling also meant the tyre was harder for
> > the same pressure as an accurately labelled tyre, so it would do a
> > better test performance (being more like an iron tyre). There is a
> > fault of those tests and why they can not be trusted
>
> May be, but it still had the lowest rr of all the tires tested that
> day! Good Luck!- Hide quoted text -
but they were not comparable tyres.
thirty-six
> Lou Holtman wrote:
> >>>> Precisely. What's the point of a RR measurement if we can't
> >>>> relate it to the real world?
> >>> The biggest and simplest reason is because what you're calling
> >>> suspension losses is a separate term, likely several terms. It
> >>> relates to empirical measures of road roughness, both amplitude
> >>> and frequency, while Crr relates only to road speed.
> >> I think this is fine, if we all accept that definition of Crr.
> >> But again, this means there is a much more important factor that
> >> almost nobody is measuring. Yes, it's harder to measure - but that
> >> doesn't mean we should pretend it doesn't matter!
> > What important factor is that Frank except tire pressure?
>
> Frank did not notice that tire pressure is already part of tire
> testing and in the curves plotted by IRC, the observant eye will note
> that these are a family of curves that almost exactly replicate each
> other if superimposed at the starting point and by use a multiplier
> can be matched at the midpoints. That alone should give the test
> credibility. I'll admit there were no microphones to record sound
> energy dissipated by the various samples. That will most likely be
> the next demand for realism that I expect... then comes odor.
No, just say what the bead to bead dimension of your super duper fast
rolling tyres were, as tested.
thirty-six
> Frank Krygowski wrote:
> >>>>>>> Precisely. What's the point of a RR measurement if we can't
> >>>>>>> relate it to the real world?
> >>>>>> The biggest and simplest reason is because what you're calling
> >>>>>> suspension losses is a separate term, likely several terms. It
> >>>>>> relates to empirical measures of road roughness, both amplitude
> >>>>>> and frequency, while Crr relates only to road speed.
> >>>>> I think this is fine, if we all accept that definition of Crr.
> >>>>> But again, this means there is a much more important factor that
> >>>>> almost nobody is measuring. Yes, it's harder to measure - but
> >>>>> that doesn't mean we should pretend it doesn't matter!
> >>>> What important factor is that Frank except tire pressure?
> >>> Width? Shape? Tire design?
> >> Yes I know that but what I meant is when there is a difference
> >> between the measurement on a steel drum and in 'the real world'
> >> what causes it?
> >> Inner tube?
> >> Of course, but lets limit ourselves to the tires.
>
> Not to worry, all the tests were done with the same inner tubes to not
> skew results. All these tires in the test were sent without tubes to
> IRC by Avocet.
What was the standard wheel used, or not?
> Jobst Brandt- Hide quoted text -
Jobst Brandt
>>>> Road roughness has nothing to do with the relative losses of
>>>> various tires...
>>> So is it your claim that the tire that shows least drag on a steel
>>> drum will definitely show the least drag on a rough, cracked,
>>> patched asphalt road?
>> If it is otherwise, you had best explain where the energy is absorbed.
> Such an adversion to the words "Yes" and "No"!
What is an "adversion" and what it say about tire RR?
> I suspect the energy is absorbed primarily in the damping action of
> human tissue. I thought that was obvious.
This subject is about tire testing, not human body reaction. It's up
top the individual to ride tires with which he is comfortable. I
haven't noticed any such discrimination in tire purchases over years of
tubulars and subsequent clinchers. Your intent seems to be to pervert
rolling resistance assessment.
Typically the Specialized Touring II, with its raised center ridge,
was a similar diversion from fact. At the time it was believed that
scrubbing of tread contact with the road was what caused rolling
resistance, so the narrower the contact patch, the lower the drag.
In RR tests that was found to be a faulty assessment because these
tires had higher RR than smooth tires with a relatively flat zone in
the round tire cross section.
> Look, if you fastened a bike to an electrically driven shaker table
> by the bike's dropouts, had a "rider" mount it, and vibrated him and
> the bike upward and downward at some reasonable distance and
> frequency (say, 5mm amplitude at 100 Hz) would that not require
> energy to drive the system?
> If the same thing happens to a rider on a rough road, would that not
> require the same energy cost?
You are diverging from tire testing to rider comfort testing. I know
that colored tires have a strong attraction these days for many
riders. It seems to be important for them, regardless of RR, the
tread being a stiff semi plastic compound.
> If other tires - softer, lower pressure ones - reduced the amplitude,
> does that not indicate less energy was lost?
Try a riding down stairs test! What does that say about tire RR?
Jobst Brandt