Large spoke tension drop with inflated tire

[tiborg]

I built a rear wheel using a DT Swiss XR 4.1d rim and tensioned the
drive side to about 120 kgf (measured with a Park Tool TM-1). After
mounting a Marathon Plus tire (47-559) and inflating to 80 psi, the
measured spoke tension dropped about 25 kgf.

I read through a long thread from a couple years ago about whether or
not to build the wheel taking into account this drop and it seemed
like the drop in tension people were seeing was relatively small. What
I'm seeing seems to be larger, so I'd like to re-open this can of
worms and ask if I should be upping the tension to compensate?

The rim's maximum recommended tension is 120kgf and the intended use
is for a full-sus bike that will run over poorly maintained roads at
30-40 km/h.

[jim beam]

Jambo wrote:
> "jim beam" <spamvortex@bad.example.net> wrote in message
> news:W-ednWXUq6LDF5ranZ2dnUVZ_oesnZ2d@speakeasy.net...
>> Jambo wrote:
>>> More like "sikorski" story, and CF noise as damage indicator, and rolled
>>> threads, and your "metarials skool", and CIA black ops classified stuff,
>>> and .....
>>>
>>> Lying ****tard.
>> well, ed, my spelling is not perfect, but it's better than yours.
>>
>> as for your other drivel, sound /is/ a reliable indicator for cfrp
>> failure,
>
> Great. Show us 1 company that uses this technique to detect CFRP failure.
>
> Even easier, show us 1 methodology used in any industry that utilizes this.
>
>> rolled threads /do/ mitigate fatigue, and many materials [and their
>> applications] have been classified for /many/ years prior to general
>> adoption.
>
> And chicken little bleatings about bicycle brake failures due to bolts with
> machined threads have been "been classified for /many/ years prior to
> general adoption" too, haven't they?
>
> Dumbass lying fraud.
>
>
>> you'd know this if you bothered to do some homework.
>
> Well, I don't subscribe to slashdot, if that's what you mean.
>
>> but given that you can't do the trivial homework that would prevent you
>> making a cock-up like "modulus is strength to weight", i guess there's not
>> much chance of you seeing the light at this stage. best you can do is
>> take your meds and try to be happy! moron.
>
> Like the homework you did on your "sikorski" story, and CF noise as damage
> indicator, and rolled
> threads, and your "metarials skool", and CIA black ops classified stuff, and
> spoke failure mechanisms, and ...
>
> DLFF.
>
>
take your meds moron. mommy will be home soon.

[Peter Cole]

tiborg wrote:
> I built a rear wheel using a DT Swiss XR 4.1d rim and tensioned the
> drive side to about 120 kgf (measured with a Park Tool TM-1). After
> mounting a Marathon Plus tire (47-559) and inflating to 80 psi, the
> measured spoke tension dropped about 25 kgf.
>
> I read through a long thread from a couple years ago about whether or
> not to build the wheel taking into account this drop and it seemed
> like the drop in tension people were seeing was relatively small. What
> I'm seeing seems to be larger, so I'd like to re-open this can of
> worms and ask if I should be upping the tension to compensate?
>
> The rim's maximum recommended tension is 120kgf and the intended use
> is for a full-sus bike that will run over poorly maintained roads at
> 30-40 km/h.
>

The compressive force of the tire will vary with the pressure and the
cross section area. You've got almost the same pressure and 4x the cross
section of a typical road tire, so you'll see a greater spoke tension
drop. You'll also get high hoop force (spreading the rim at the bead),
make sure your rims can take that.

[jim beam]

tiborg wrote:
> I built a rear wheel using a DT Swiss XR 4.1d rim and tensioned the
> drive side to about 120 kgf (measured with a Park Tool TM-1). After
> mounting a Marathon Plus tire (47-559) and inflating to 80 psi, the
> measured spoke tension dropped about 25 kgf.
>
> I read through a long thread from a couple years ago about whether or
> not to build the wheel taking into account this drop and it seemed
> like the drop in tension people were seeing was relatively small. What
> I'm seeing seems to be larger, so I'd like to re-open this can of
> worms and ask if I should be upping the tension to compensate?
>
> The rim's maximum recommended tension is 120kgf and the intended use
> is for a full-sus bike that will run over poorly maintained roads at
> 30-40 km/h.
>
write to carl fogel about this - he's done more investigation on this
topic than anyone else that i've seen.

in answer to your question, no, do not "up" the tension to compensate.
rim manufacturers determine spoke tension specs from empirical testing.
that means running a rim as part of a loaded wheel with an inflated
tire on it.

[carlfogel@comcast.net]

On Mon, 01 Oct 2007 06:41:47 -0700, tiborg <tcg001@mac.com> wrote:

>I built a rear wheel using a DT Swiss XR 4.1d rim and tensioned the
>drive side to about 120 kgf (measured with a Park Tool TM-1). After
>mounting a Marathon Plus tire (47-559) and inflating to 80 psi, the
>measured spoke tension dropped about 25 kgf.
>
>I read through a long thread from a couple years ago about whether or
>not to build the wheel taking into account this drop and it seemed
>like the drop in tension people were seeing was relatively small. What
>I'm seeing seems to be larger, so I'd like to re-open this can of
>worms and ask if I should be upping the tension to compensate?
>
>The rim's maximum recommended tension is 120kgf and the intended use
>is for a full-sus bike that will run over poorly maintained roads at
>30-40 km/h.

Dear T,

Some reviews of the rim:

http://www.mtbr.com/reviews/Rim/product_122485.shtml

Google suggests that you have a 32 or 36 spoke 26" 425 gram
box-section clincher rim designed for disk brakes only (no rim wear):

http://www.go-ride.com/prod_rims.html

With a wide tire inflated as high as 80 psi, a box-section clincher as
wide as your rim may well drop 25 kg of spoke tension from 120 kgf.

But that 80 psi does sound awfully high. In fact, you're about 14%
over Schwalbe's maximum suggested 70 psi for that tire:

http://www.schwalbetires.com/node/142/ok

I'd think hard about why I needed 80 psi on a 47 mm nominal width tire
when I was running full suspension. If I really needed that much
inflation because of weight or impact flats, I'd try to find a wider
rim, a wider tire, or a rim with more spokes, not over-inflate the
tire and over-tension the spokes.

In any case, I wouldn't try to tension spokes according to how much
the tension drops after the tire is inflated.

I've realized that I have no idea how manufacturers arrive at their
recommended maximum rim tensions, but I suspect that they aim at bare
rims.

Even if you use Jobst's method of raising tension until the rim goes
out of true when spoke pairs are squeezed and then backing off a
little, remember that Jobst doesn't try for higher tension with the
tire inflated--he works on bare rims.

The obvious reason is that a flat tire would make the wheel go boing!
You'd have to re-true the rim on the spot because the spoke tension
would jump past the bare rim's practical limit.

In other words, I wouldn't want to be riding a bike at 25 mph on a bad
road when a flat tire caused my spoke tension to jump 25 kgf past the
rim's 125 kgf recommended tension, particularly when I don't know
whether the manufacturer has already factored in some tire-inflation
tension-drop.

Cheers,

Carl Fogel

[jim beam]

Peter Cole wrote:
> tiborg wrote:
>> I built a rear wheel using a DT Swiss XR 4.1d rim and tensioned the
>> drive side to about 120 kgf (measured with a Park Tool TM-1). After
>> mounting a Marathon Plus tire (47-559) and inflating to 80 psi, the
>> measured spoke tension dropped about 25 kgf.
>>
>> I read through a long thread from a couple years ago about whether or
>> not to build the wheel taking into account this drop and it seemed
>> like the drop in tension people were seeing was relatively small. What
>> I'm seeing seems to be larger, so I'd like to re-open this can of
>> worms and ask if I should be upping the tension to compensate?
>>
>> The rim's maximum recommended tension is 120kgf and the intended use
>> is for a full-sus bike that will run over poorly maintained roads at
>> 30-40 km/h.
>>
>
> The compressive force of the tire will vary with the pressure and the
> cross section area. You've got almost the same pressure and 4x the cross
> section of a typical road tire, so you'll see a greater spoke tension
> drop. You'll also get high hoop force (spreading the rim at the bead),
> make sure your rims can take that.

he said, completely avoiding the op's question...

[Peter Cole]

jim beam wrote:
> tiborg wrote:
>> I built a rear wheel using a DT Swiss XR 4.1d rim and tensioned the
>> drive side to about 120 kgf (measured with a Park Tool TM-1). After
>> mounting a Marathon Plus tire (47-559) and inflating to 80 psi, the
>> measured spoke tension dropped about 25 kgf.
>>
>> I read through a long thread from a couple years ago about whether or
>> not to build the wheel taking into account this drop and it seemed
>> like the drop in tension people were seeing was relatively small. What
>> I'm seeing seems to be larger, so I'd like to re-open this can of
>> worms and ask if I should be upping the tension to compensate?
>>
>> The rim's maximum recommended tension is 120kgf and the intended use
>> is for a full-sus bike that will run over poorly maintained roads at
>> 30-40 km/h.
>>
> write to carl fogel about this - he's done more investigation on this
> topic than anyone else that i've seen.
>
> in answer to your question, no, do not "up" the tension to compensate.
> rim manufacturers determine spoke tension specs from empirical testing.
> that means running a rim as part of a loaded wheel with an inflated
> tire on it.

Typical XC tires don't run at 80lb.

[Jambo]

"jim beam" <spamvortex@bad.example.net> wrote in message
news:QNydnS2bmvftXJzanZ2dnUVZ_o3inZ2d@speakeasy.ne t...
> in answer to your question, no, do not "up" the tension to compensate. rim
> manufacturers determine spoke tension specs from empirical testing. that
> means running a rim as part of a loaded wheel with an inflated tire on it.

Whaddaya know, beamboy borrows from JB's book again...

[Peter Cole]

jim beam wrote:
> Peter Cole wrote:
>> tiborg wrote:
>>> I built a rear wheel using a DT Swiss XR 4.1d rim and tensioned the
>>> drive side to about 120 kgf (measured with a Park Tool TM-1). After
>>> mounting a Marathon Plus tire (47-559) and inflating to 80 psi, the
>>> measured spoke tension dropped about 25 kgf.
>>>
>>> I read through a long thread from a couple years ago about whether or
>>> not to build the wheel taking into account this drop and it seemed
>>> like the drop in tension people were seeing was relatively small. What
>>> I'm seeing seems to be larger, so I'd like to re-open this can of
>>> worms and ask if I should be upping the tension to compensate?
>>>
>>> The rim's maximum recommended tension is 120kgf and the intended use
>>> is for a full-sus bike that will run over poorly maintained roads at
>>> 30-40 km/h.
>>>
>>
>> The compressive force of the tire will vary with the pressure and the
>> cross section area. You've got almost the same pressure and 4x the
>> cross section of a typical road tire, so you'll see a greater spoke
>> tension drop. You'll also get high hoop force (spreading the rim at
>> the bead), make sure your rims can take that.
>
> he said, completely avoiding the op's question...

I'm unfamiliar with the rim. If it was a Mavic, I'd say no. Off hand,
I'd say unless you're pushing the load limit of the wheel, I don't see
the point in obsessing about getting the maximum possible spoke tension
-- but others may disagree -- so my answer would only be a personal
preference.

I doubt that it would cause any harm to bump up the spoke tension, but
since he's nominally running a normal size MTB tire at twice typical
pressure, I'd bump it up by half the tension drop he's seeing ~12kg.

There is a real danger in running very large tires at high pressure. I
wouldn't push that limit myself, especially with a lightweight rim.

[tiborg]

On Oct 2, 1:56 pm, carlfo...@comcast.net wrote:
> But that 80 psi does sound awfully high. In fact, you're about 14%
> over Schwalbe's maximum suggested 70 psi for that tire:
>
> http://www.schwalbetires.com/node/142/ok
>
> I'd think hard about why I needed 80 psi on a 47 mm nominal width tire
> when I was running full suspension. If I really needed that much
> inflation because of weight or impact flats, I'd try to find a wider
> rim, a wider tire, or a rim with more spokes, not over-inflate the
> tire and over-tension the spokes.

Thanks for catching this, I did mean to inflate the tire up to the max
rating but in the time between reading the markings on the tire and
setting the indicator ring on my pump, the number may have been
corrupted in my head.

My reasoning for the high pressure is because I have a suspension on
the frame, I shouldn't need to rely on the tire for any buffering.
Therefore, I'm trying to maximize the rolling efficiency (as absurd as
that sounds when talking about a full suspension bike carrying
panniers stuffed with clothing and tools and riding on a tire that has
a 1 cm thick rubber lining).

> In any case, I wouldn't try to tension spokes according to how much
> the tension drops after the tire is inflated.
>
> I've realized that I have no idea how manufacturers arrive at their
> recommended maximum rim tensions, but I suspect that they aim at bare
> rims.
>

This makes sense since there they cannot easily account for the
variety in tires and pressures that will be used on their rims.

> Even if you use Jobst's method of raising tension until the rim goes
> out of true when spoke pairs are squeezed and then backing off a
> little, remember that Jobst doesn't try for higher tension with the
> tire inflated--he works on bare rims.
>
> The obvious reason is that a flat tire would make the wheel go boing!
> You'd have to re-true the rim on the spot because the spoke tension
> would jump past the bare rim's practical limit.
>
> In other words, I wouldn't want to be riding a bike at 25 mph on a bad
> road when a flat tire caused my spoke tension to jump 25 kgf past the
> rim's 125 kgf recommended tension, particularly when I don't know
> whether the manufacturer has already factored in some tire-inflation
> tension-drop.
>

Hmm, a possible experiment for Fogel labs?

> Cheers,
>
> Carl Fogel

[carlfogel@comcast.net]

On Tue, 02 Oct 2007 00:11:51 -0700, tiborg <tcg001@mac.com> wrote:

>On Oct 2, 1:56 pm, carlfo...@comcast.net wrote:
>> But that 80 psi does sound awfully high. In fact, you're about 14%
>> over Schwalbe's maximum suggested 70 psi for that tire:
>>
>> http://www.schwalbetires.com/node/142/ok
>>
>> I'd think hard about why I needed 80 psi on a 47 mm nominal width tire
>> when I was running full suspension. If I really needed that much
>> inflation because of weight or impact flats, I'd try to find a wider
>> rim, a wider tire, or a rim with more spokes, not over-inflate the
>> tire and over-tension the spokes.
>
>Thanks for catching this, I did mean to inflate the tire up to the max
>rating but in the time between reading the markings on the tire and
>setting the indicator ring on my pump, the number may have been
>corrupted in my head.
>
>My reasoning for the high pressure is because I have a suspension on
>the frame, I shouldn't need to rely on the tire for any buffering.
>Therefore, I'm trying to maximize the rolling efficiency (as absurd as
>that sounds when talking about a full suspension bike carrying
>panniers stuffed with clothing and tools and riding on a tire that has
>a 1 cm thick rubber lining).
>
>> In any case, I wouldn't try to tension spokes according to how much
>> the tension drops after the tire is inflated.
>>
>> I've realized that I have no idea how manufacturers arrive at their
>> recommended maximum rim tensions, but I suspect that they aim at bare
>> rims.
>>
>
>This makes sense since there they cannot easily account for the
>variety in tires and pressures that will be used on their rims.
>
>> Even if you use Jobst's method of raising tension until the rim goes
>> out of true when spoke pairs are squeezed and then backing off a
>> little, remember that Jobst doesn't try for higher tension with the
>> tire inflated--he works on bare rims.
>>
>> The obvious reason is that a flat tire would make the wheel go boing!
>> You'd have to re-true the rim on the spot because the spoke tension
>> would jump past the bare rim's practical limit.
>>
>> In other words, I wouldn't want to be riding a bike at 25 mph on a bad
>> road when a flat tire caused my spoke tension to jump 25 kgf past the
>> rim's 125 kgf recommended tension, particularly when I don't know
>> whether the manufacturer has already factored in some tire-inflation
>> tension-drop.
>>
>
>Hmm, a possible experiment for Fogel labs?
>
>> Cheers,
>>
>> Carl Fogel

Dear T,

I suspect that full suspension losses would overshadow any slight
improvement in rolling resistance gained by high inflation.

I really do wonder how rim makers arrive at their modern maximum
recommended tension. I've never seen anything specific about it. They
may have elaborate road tests, complicated laboratory equipment, or
just some guy with a tension gauge and a well-thumbed copy of "The
Bicycle Wheel" who keeps turning the spoke nipples until the rim tacos
when he squeezes spoke pairs or he notices the spokes turning into
barber poles.

Whatever the method, there's probably a practical fudge factor. Rims
are extruded through dies that wear, so the last rim through the die
may be as much as 10% heavier (and stronger) than the first.

Concerning your hopes for an experiment at 25 mph on what sounds like
a dirt road, Fogel Labs uses about 6 psi with full suspension and
declines to test anything less than a 4x18 trials tread tire on the
rear.

An impromptu test in Baja in 1972 showed that a skinnier 3.50 x 18
tire would last only 180 miles on rough dirt roads when flat. The
spokes were re-tightened and loc-tited at about 90 miles and the wheel
survived for later riding, but the flat tire came apart, snarling
everything with bead wire.

More enthusiastic (or perhaps even less intelligent) testers have run
greater distances on bare rims at much higher speeds in Baja without
even a flat tire for padding, an amazing example of how sturdy
Husqvarna desert race wheels were in those days. I hate to think what
Husqvarna did to show how tough their sewing machines were--maybe they
embroidered their logo on the side of Sherman tank turret?

The RBT wheel-building wars are pretty much unknown in the motorcycle
world, where engine power means that there's no need to build fragile
wheels.

Cheers,

Carl Fogel

[Chalo]

tiborg wrote:
>
> Carl Fogel wrote:
> >
> > I'd think hard about why I needed 80 psi on a 47 mm nominal width tire
> > when I was running full suspension. If I really needed that much
> > inflation because of weight or impact flats, I'd try to find a wider
> > rim, a wider tire, or a rim with more spokes, not over-inflate the
> > tire and over-tension the spokes.
>
> Thanks for catching this, I did mean to inflate the tire up to the max
> rating but in the time between reading the markings on the tire and
> setting the indicator ring on my pump, the number may have been
> corrupted in my head.
>
> My reasoning for the high pressure is because I have a suspension on
> the frame, I shouldn't need to rely on the tire for any buffering.
> Therefore, I'm trying to maximize the rolling efficiency (as absurd as
> that sounds when talking about a full suspension bike carrying
> panniers stuffed with clothing and tools and riding on a tire that has
> a 1 cm thick rubber lining).

My experience with the Schwalbe Marathon Plus was problematic. I used
the 40-622 size on my electric-assist bike with a gross weight of just
over 500 pounds. Because of the heavy load, and because of the ride-
softening effect of the elastomer belt, I ran them at higher than
recommended pressure-- about 90psi, but I do not remember precisely.
Two tires suffered casing failures at the bead wires (the fabric
stripped off the wires), resulting in tremendous blowouts. After I
lowered the pressure to within the sidewall rating, a third tire
suffered a major sidewall bulge from an internal casing failure. All
three of these failures occurred after minimal mileage.

I was never able to determine whether the batch I got was faulty, and
because I was loading the bike well beyond the tire's intended
capacity, I did not pursue warranty replacement.

The moral of my story is that, if my experience is any guide, you
probably shouldn't inflate those tires in excess of their rating. I
wouldn't even run them at their maximum pressure rating, because their
traction and wear should be better at a lower pressure, with
negligible added rolling resistance.

My casual experiments with some fat street tires lately seem to
indicate that rolling resistance does not diminish noticeably between
modest and very high pressures. My hypothesis is that a very fat tire
need not deform much even if the pressure is relatively low, and the
reduction of losses as bumps and jolts more or less offsets any
increase in tire losses.

There's certainly no harm in trying your tires for a while at 70psi
and then at 45-50psi to see if you can detect any loss in speed or
increased times over familiar routes.

Chalo

[Michael Press]

In article
<1191309111.049739.209590@k79g2000hse.googlegroups. com>
,
tiborg <tcg001@mac.com> wrote:

> On Oct 2, 1:56 pm, carlfo...@comcast.net wrote:
> > But that 80 psi does sound awfully high. In fact, you're about 14%
> > over Schwalbe's maximum suggested 70 psi for that tire:
> >
> > http://www.schwalbetires.com/node/142/ok
> >
> > I'd think hard about why I needed 80 psi on a 47 mm nominal width tire
> > when I was running full suspension. If I really needed that much
> > inflation because of weight or impact flats, I'd try to find a wider
> > rim, a wider tire, or a rim with more spokes, not over-inflate the
> > tire and over-tension the spokes.
>
> Thanks for catching this, I did mean to inflate the tire up to the max
> rating but in the time between reading the markings on the tire and
> setting the indicator ring on my pump, the number may have been
> corrupted in my head.
>
> My reasoning for the high pressure is because I have a suspension on
> the frame, I shouldn't need to rely on the tire for any buffering.
> Therefore, I'm trying to maximize the rolling efficiency (as absurd as
> that sounds when talking about a full suspension bike carrying
> panniers stuffed with clothing and tools and riding on a tire that has
> a 1 cm thick rubber lining).

Anything worth doing is worth overdoing. :)

--
Michael Press

[tiborg]

On Oct 2, 5:01 pm, Chalo <chalo.col...@gmail.com> wrote:
> tiborg wrote:
>
> > Carl Fogel wrote:
>
> > > I'd think hard about why I needed 80 psi on a 47 mm nominal width tire
> > > when I was running full suspension. If I really needed that much
> > > inflation because of weight or impact flats, I'd try to find a wider
> > > rim, a wider tire, or a rim with more spokes, not over-inflate the
> > > tire and over-tension the spokes.
>
> > Thanks for catching this, I did mean to inflate the tire up to the max
> > rating but in the time between reading the markings on the tire and
> > setting the indicator ring on my pump, the number may have been
> > corrupted in my head.
>
> > My reasoning for the high pressure is because I have a suspension on
> > the frame, I shouldn't need to rely on the tire for any buffering.
> > Therefore, I'm trying to maximize the rolling efficiency (as absurd as
> > that sounds when talking about a full suspension bike carrying
> > panniers stuffed with clothing and tools and riding on a tire that has
> > a 1 cm thick rubber lining).
>
> My experience with the Schwalbe Marathon Plus was problematic. I used
> the 40-622 size on my electric-assist bike with a gross weight of just
> over 500 pounds. Because of the heavy load, and because of the ride-
> softening effect of the elastomer belt, I ran them at higher than
> recommended pressure-- about 90psi, but I do not remember precisely.
> Two tires suffered casing failures at the bead wires (the fabric
> stripped off the wires), resulting in tremendous blowouts. After I
> lowered the pressure to within the sidewall rating, a third tire
> suffered a major sidewall bulge from an internal casing failure. All
> three of these failures occurred after minimal mileage.
>
> I was never able to determine whether the batch I got was faulty, and
> because I was loading the bike well beyond the tire's intended
> capacity, I did not pursue warranty replacement.
>
> The moral of my story is that, if my experience is any guide, you
> probably shouldn't inflate those tires in excess of their rating. I
> wouldn't even run them at their maximum pressure rating, because their
> traction and wear should be better at a lower pressure, with
> negligible added rolling resistance.
>
> My casual experiments with some fat street tires lately seem to
> indicate that rolling resistance does not diminish noticeably between
> modest and very high pressures. My hypothesis is that a very fat tire
> need not deform much even if the pressure is relatively low, and the
> reduction of losses as bumps and jolts more or less offsets any
> increase in tire losses.
>
> There's certainly no harm in trying your tires for a while at 70psi
> and then at 45-50psi to see if you can detect any loss in speed or
> increased times over familiar routes.
>
> Chalo

Well I'm happy to report that I was in error in stating I had the tire
inflated to 80 psi, it is in fact running at 70. When I first tried
this tire out, I was running it 60 psi and boosted it up to 70 about a
month ago. As I stated above, the idea was to see if I could do
without the tire's inherent suspension and only rely on that of the
bike (2005 Giant Reign 3 - Japan export model).

My daily round-trip distance is only 40km, so any gains of the higher
pressure are likely offset by having to stop for one extra feral ninja
cat on any given day. However, in the pursuit of an ever smoother
ride, I will take your suggestion of dropping the pressure
considerably and see how that suits me.

[Tim McNamara]

In article <1191312069.550241.130520@w3g2000hsg.googlegroups.c om>,
Chalo <chalo.colina@gmail.com> wrote:

> My casual experiments with some fat street tires lately seem to
> indicate that rolling resistance does not diminish noticeably between
> modest and very high pressures. My hypothesis is that a very fat
> tire need not deform much even if the pressure is relatively low, and
> the reduction of losses as bumps and jolts more or less offsets any
> increase in tire losses.

That's not inconsistent with the rolling resistance tests that compared
inflation pressures. On those curves, there is quite a bit of
flattening of the curve between medium and high pressures compared to
low and medium pressures. Jan Heine found the same thing, that medium
pressures don't seem to result in a large increase in rolling resistance
compared to high pressures.

[tiborg]

On Oct 2, 5:01 pm, Chalo <chalo.col...@gmail.com> wrote:
> tiborg wrote:
>
> > Carl Fogel wrote:
>
> > > I'd think hard about why I needed 80 psi on a 47 mm nominal width tire
> > > when I was running full suspension. If I really needed that much
> > > inflation because of weight or impact flats, I'd try to find a wider
> > > rim, a wider tire, or a rim with more spokes, not over-inflate the
> > > tire and over-tension the spokes.
>
> > Thanks for catching this, I did mean to inflate the tire up to the max
> > rating but in the time between reading the markings on the tire and
> > setting the indicator ring on my pump, the number may have been
> > corrupted in my head.
>
> > My reasoning for the high pressure is because I have a suspension on
> > the frame, I shouldn't need to rely on the tire for any buffering.
> > Therefore, I'm trying to maximize the rolling efficiency (as absurd as
> > that sounds when talking about a full suspension bike carrying
> > panniers stuffed with clothing and tools and riding on a tire that has
> > a 1 cm thick rubber lining).
>
> My experience with the Schwalbe Marathon Plus was problematic. I used
> the 40-622 size on my electric-assist bike with a gross weight of just
> over 500 pounds. Because of the heavy load, and because of the ride-
> softening effect of the elastomer belt, I ran them at higher than
> recommended pressure-- about 90psi, but I do not remember precisely.
> Two tires suffered casing failures at the bead wires (the fabric
> stripped off the wires), resulting in tremendous blowouts. After I
> lowered the pressure to within the sidewall rating, a third tire
> suffered a major sidewall bulge from an internal casing failure. All
> three of these failures occurred after minimal mileage.
>
> I was never able to determine whether the batch I got was faulty, and
> because I was loading the bike well beyond the tire's intended
> capacity, I did not pursue warranty replacement.
>
> The moral of my story is that, if my experience is any guide, you
> probably shouldn't inflate those tires in excess of their rating. I
> wouldn't even run them at their maximum pressure rating, because their
> traction and wear should be better at a lower pressure, with
> negligible added rolling resistance.
>
> My casual experiments with some fat street tires lately seem to
> indicate that rolling resistance does not diminish noticeably between
> modest and very high pressures. My hypothesis is that a very fat tire
> need not deform much even if the pressure is relatively low, and the
> reduction of losses as bumps and jolts more or less offsets any
> increase in tire losses.
>
> There's certainly no harm in trying your tires for a while at 70psi
> and then at 45-50psi to see if you can detect any loss in speed or
> increased times over familiar routes.
>
> Chalo

50psi worked out great. Didn't notice any extra effort and it almost
completely eliminated the road buzz from an overpass covered in 10cm
tiles. Spoke tension went up about 5kgf with the lower pressure.

[Tom \Johnny Sunset\ Sherman]

Peter Cole wrote:
> ...
> There is a real danger in running very large tires at high pressure. I
> wouldn't push that limit myself, especially with a lightweight rim.

I use 53-406 Maxxis Hookworm tires on Velocity Taipan rims at 7.5 bar
(110 psi) for my trike. I will see if the rims eventually split [1].

[1] The front wheels have disc brakes, while the rear wheel lacks a
brake, so there will be no brake track wear.

--
Tom Sherman - Holstein-Friesland Bovinia
A Real Cyclist [TM] keeps at least one bicycle in the bedroom.

--
Posted via a free Usenet account from http://www.teranews.com

[Tom \Johnny Sunset\ Sherman]

Peter Cole wrote:
> jim beam wrote:
>> tiborg wrote:
>>> I built a rear wheel using a DT Swiss XR 4.1d rim and tensioned the
>>> drive side to about 120 kgf (measured with a Park Tool TM-1). After
>>> mounting a Marathon Plus tire (47-559) and inflating to 80 psi, the
>>> measured spoke tension dropped about 25 kgf.
>>>
>>> I read through a long thread from a couple years ago about whether or
>>> not to build the wheel taking into account this drop and it seemed
>>> like the drop in tension people were seeing was relatively small. What
>>> I'm seeing seems to be larger, so I'd like to re-open this can of
>>> worms and ask if I should be upping the tension to compensate?
>>>
>>> The rim's maximum recommended tension is 120kgf and the intended use
>>> is for a full-sus bike that will run over poorly maintained roads at
>>> 30-40 km/h.
>>>
>> write to carl fogel about this - he's done more investigation on this
>> topic than anyone else that i've seen.
>>
>> in answer to your question, no, do not "up" the tension to compensate.
>> rim manufacturers determine spoke tension specs from empirical
>> testing. that means running a rim as part of a loaded wheel with an
>> inflated tire on it.
>
> Typical XC tires don't run at 80lb.

However, BMX freestyle tires [1] are typically 44 to 53 mm in nominal
width, with maximum inflation pressures of 6 to 9 bar (90 to 130 psi) [2].

[1] Often the best road tire choice for small wheel recumbents.
[2] The Snafu Rim Job is an example of the latter case.

--
Tom Sherman - Holstein-Friesland Bovinia
A Real Cyclist [TM] keeps at least one bicycle in the bedroom.

--
Posted via a free Usenet account from http://www.teranews.com

[jim beam]

Jambo wrote:
> "jim beam" <spamvortex@bad.example.net> wrote in message
> news:QNydnS2bmvftXJzanZ2dnUVZ_o3inZ2d@speakeasy.ne t...
>> in answer to your question, no, do not "up" the tension to compensate. rim
>> manufacturers determine spoke tension specs from empirical testing. that
>> means running a rim as part of a loaded wheel with an inflated tire on it.
>
> Whaddaya know, beamboy borrows from JB's book again...
>
>
eh? you're making no sense. moron.

[Chalo]

Tom \"Johnny Sunset\" Sherman" wrote:
>
> Peter Cole wrote:
> > ...
> > There is a real danger in running very large tires at high pressure. I
> > wouldn't push that limit myself, especially with a lightweight rim.
>
> I use 53-406 Maxxis Hookworm tires on Velocity Taipan rims at 7.5 bar
> (110 psi) for my trike. I will see if the rims eventually split [1].

I don't know about the Taipan, but many freestyle rims are made for
such pressures.

I doubt that you are benefiting from such high pressure, though.
Freestylers use it to keep from pinching tubes when they land on
square-edged steps, coping, and curbs. I bet that you could let that
tire down 40-50 lbs and not see any difference in speed. A Primo
Comet 20 x 2.1" would probably be faster, even at 60psi.

Chalo

[Mike Jacoubowsky]

> I use 53-406 Maxxis Hookworm tires on Velocity Taipan rims at 7.5 bar (110
> psi) for my trike. I will see if the rims eventually split [1].

They will. It's just a matter of time. We've dealt with this issue for one
of our customers (he has a Trek R200 recumbent we sold him, which he uses
for commuting). Lowering the pressure to 80psi has helped. He's split three
so far, and considers it simply a cost of ownership issue; if he wants both
the surface area of a wide tire and low rolling resistance, he doesn't have
much choice.

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


"Tom "Johnny Sunset" Sherman" <sunsetss0003@iinvalid.com> wrote in message
news:4702e2d1$0$26403$88260bb3@free.teranews.com.. .
> Peter Cole wrote:
>> ...
>> There is a real danger in running very large tires at high pressure. I
>> wouldn't push that limit myself, especially with a lightweight rim.
>
> I use 53-406 Maxxis Hookworm tires on Velocity Taipan rims at 7.5 bar (110
> psi) for my trike. I will see if the rims eventually split [1].
>
> [1] The front wheels have disc brakes, while the rear wheel lacks a brake,
> so there will be no brake track wear.
>
> --
> Tom Sherman - Holstein-Friesland Bovinia
> A Real Cyclist [TM] keeps at least one bicycle in the bedroom.
>
> --
> Posted via a free Usenet account from http://www.teranews.com
>
>

[Peter Cole]

Tom "Johnny Sunset" Sherman wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> tiborg wrote:
>>>> I built a rear wheel using a DT Swiss XR 4.1d rim and tensioned the
>>>> drive side to about 120 kgf (measured with a Park Tool TM-1). After
>>>> mounting a Marathon Plus tire (47-559) and inflating to 80 psi, the
>>>> measured spoke tension dropped about 25 kgf.
>>>>
>>>> I read through a long thread from a couple years ago about whether or
>>>> not to build the wheel taking into account this drop and it seemed
>>>> like the drop in tension people were seeing was relatively small. What
>>>> I'm seeing seems to be larger, so I'd like to re-open this can of
>>>> worms and ask if I should be upping the tension to compensate?
>>>>
>>>> The rim's maximum recommended tension is 120kgf and the intended use
>>>> is for a full-sus bike that will run over poorly maintained roads at
>>>> 30-40 km/h.
>>>>
>>> write to carl fogel about this - he's done more investigation on this
>>> topic than anyone else that i've seen.
>>>
>>> in answer to your question, no, do not "up" the tension to
>>> compensate. rim manufacturers determine spoke tension specs from
>>> empirical testing. that means running a rim as part of a loaded
>>> wheel with an inflated tire on it.
>>
>> Typical XC tires don't run at 80lb.
>
> However, BMX freestyle tires [1] are typically 44 to 53 mm in nominal
> width, with maximum inflation pressures of 6 to 9 bar (90 to 130 psi) [2].
>
> [1] Often the best road tire choice for small wheel recumbents.
> [2] The Snafu Rim Job is an example of the latter case.
>

He was using XC (MTB) rims. I think those tires and pressures might be
outside of the design expectations, but I don't know if the maker specs
that.

[Jambo]

"jim beam" <spamvortex@bad.example.net> wrote in message
news:NvednVCG6NIAiJ7anZ2dnUVZ_v_inZ2d@speakeasy.ne t...
> Jambo wrote:
>> "jim beam" <spamvortex@bad.example.net> wrote in message
>> news:QNydnS2bmvftXJzanZ2dnUVZ_o3inZ2d@speakeasy.ne t...
>>> in answer to your question, no, do not "up" the tension to compensate.
>>> rim manufacturers determine spoke tension specs from empirical testing.
>>> that means running a rim as part of a loaded wheel with an inflated tire
>>> on it.
>>
>> Whaddaya know, beamboy borrows from JB's book again...
> eh? you're making no sense. moron.

Sure I am, and you know it, beamboy.

[bjw@mambo.ucolick.org]

On Oct 2, 10:56 pm, Chalo <chalo.col...@gmail.com> wrote:
> Tom \"Johnny Sunset\" Sherman" wrote:
>
> > I use 53-406 Maxxis Hookworm tires on Velocity Taipan rims at 7.5 bar
> > (110 psi) for my trike. I will see if the rims eventually split [1].
>
> I don't know about the Taipan, but many freestyle rims are made for
> such pressures.
>
> I doubt that you are benefiting from such high pressure, though.
> Freestylers use it to keep from pinching tubes when they land on
> square-edged steps, coping, and curbs. I bet that you could let that
> tire down 40-50 lbs and not see any difference in speed. A Primo
> Comet 20 x 2.1" would probably be faster, even at 60psi.
>

You think so, but you haven't seen the speed at
which Tom rides down steps or curb-hops on his trike.
Freestyling on a machine like that, you can't always
land gently.

Ben

[Tom \Johnny Sunset\ Sherman]

Chalo Colina wrote:
> Tom \"Johnny Sunset\" Sherman" wrote:
>> Peter Cole wrote:
>>> ...
>>> There is a real danger in running very large tires at high pressure. I
>>> wouldn't push that limit myself, especially with a lightweight rim.
>> I use 53-406 Maxxis Hookworm tires on Velocity Taipan rims at 7.5 bar
>> (110 psi) for my trike. I will see if the rims eventually split [1].
>
> I don't know about the Taipan, but many freestyle rims are made for
> such pressures.
>
> I doubt that you are benefiting from such high pressure, though.
> Freestylers use it to keep from pinching tubes when they land on
> square-edged steps, coping, and curbs. I bet that you could let that
> tire down 40-50 lbs and not see any difference in speed. A Primo
> Comet 20 x 2.1" would probably be faster, even at 60psi.

If I want to go fast, I do not ride the trike. If I want to be able to
watch the scenery and pretty much ignore the road surface, I ride the
trike. However, the Hookworms, with their massive (for a bicycle tire)
casings do seem to get draggy at lower pressures (unlike the Avocet
Freestyle and Mitsuboshi Tioga Comp Pool).

Primo Comets are fragile and have poor wet weather traction. That being
said, I have descended at 90+ kph on a bicycle with a 35-305 Primo Comet
front tire [1] inflated to 6.5 bar (~95 psi). ;)

[1] Much to the amazement of the flock of Kestrels (OK, their riders) I
passed one time.

--
Tom Sherman - Holstein-Friesland Bovinia
A Real Cyclist [TM] keeps at least one bicycle in the bedroom.

--
Posted via a free Usenet account from http://www.teranews.com

[Tom \Johnny Sunset\ Sherman]

bjw@mambo.ucolick.org wrote:
> On Oct 2, 10:56 pm, Chalo <chalo.col...@gmail.com> wrote:
>> Tom \"Johnny Sunset\" Sherman" wrote:
>>
>>> I use 53-406 Maxxis Hookworm tires on Velocity Taipan rims at 7.5 bar
>>> (110 psi) for my trike. I will see if the rims eventually split [1].
>> I don't know about the Taipan, but many freestyle rims are made for
>> such pressures.
>>
>> I doubt that you are benefiting from such high pressure, though.
>> Freestylers use it to keep from pinching tubes when they land on
>> square-edged steps, coping, and curbs. I bet that you could let that
>> tire down 40-50 lbs and not see any difference in speed. A Primo
>> Comet 20 x 2.1" would probably be faster, even at 60psi.
>>
>
> You think so, but you haven't seen the speed at
> which Tom rides down steps or curb-hops on his trike.
> Freestyling on a machine like that, you can't always
> land gently.

Well, not exactly. ;)

--
Tom Sherman - Holstein-Friesland Bovinia
A Real Cyclist [TM] keeps at least one bicycle in the bedroom.

--
Posted via a free Usenet account from http://www.teranews.com

[jim beam]

Jambo wrote:
> "jim beam" <spamvortex@bad.example.net> wrote in message
> news:NvednVCG6NIAiJ7anZ2dnUVZ_v_inZ2d@speakeasy.ne t...
>> Jambo wrote:
>>> "jim beam" <spamvortex@bad.example.net> wrote in message
>>> news:QNydnS2bmvftXJzanZ2dnUVZ_o3inZ2d@speakeasy.ne t...
>>>> in answer to your question, no, do not "up" the tension to compensate.
>>>> rim manufacturers determine spoke tension specs from empirical testing.
>>>> that means running a rim as part of a loaded wheel with an inflated tire
>>>> on it.
>>> Whaddaya know, beamboy borrows from JB's book again...
>> eh? you're making no sense. moron.
>
> Sure I am, and you know it, beamboy.
>
>
love it! invent crap - use it like it's not imaginary! just like your
materials theory. "modulus is strength to weight", remember? moron.

[Anthony King]

It looks like the OP found out what almost everyone discovers when
they are able to clear their heads of the endlessly repeated falsehood
that higher air pressure equals significantly less rolling resistance.

There is a nice chart made by Frank Berto that determines what air
pressure will yield 15% tire drop according to the tire's width and
the weight on each wheel of the bike. 15% tire drop is good starting
(and usually ending) point, as less yields insignificant decreases in
rolling resistance (and on some less than smooth surfaces actually
increases rolling resistance). The recommended air pressure is almost
always significantly less than people expect. The chart isn't the end-
all be-all, as different surfaces and types of riding call for fine
tuning, but it is a much better starting point than what the average
"knowledgeable" cyclist or bike shop worker--who generally
overinflates his tires far beyond the point at which any significant
decrease in rolling resistance is achieved--recommends.

The chart first appeared in Austrian Cyclist March/April of 2004 and
was reprinted in Bicycle Quarterly Vol. 5 Number 4. I am unsure if an
internet source exists, but I've found it a valueable reference as I
set up bikes for a wide variety of riders.
---------------
As for manufacturers recommended spoke tensions, I know some well
known manufacturers who recommend the same tension for all of their
rims, while it is obvious than all their rims aren't equally strong.
110-120kgf will hardly ever do you wrong on modern double wall alloy
rims.

Anthony King
----------------------
Trinity Bicycles
www.trinitybicycles.com
437 E. Pioneer Dr. #160
Irving, TX 75061
972.721.7090
Bicycles, parts, and handbuilt wheels for those who value proven and
practical performance.

[Tim McNamara]

In article <1191613840.119960.166770@d55g2000hsg.googlegroups. com>,
Anthony King <trinitybicycles@gmail.com> wrote:

> It looks like the OP found out what almost everyone discovers when
> they are able to clear their heads of the endlessly repeated
> falsehood that higher air pressure equals significantly less rolling
> resistance.

It's relative. The difference between 30 psi and 70 psi is greater than
the difference between 70 psi and 110 psi. If you look at the old
rolling resistance measurements from Avocet 20+ years ago, you'll notice
that the curves flatten quite a bit at higher pressures. It's the same
phenomenon.

> There is a nice chart made by Frank Berto that determines what air
> pressure will yield 15% tire drop according to the tire's width and
> the weight on each wheel of the bike. 15% tire drop is good starting
> (and usually ending) point, as less yields insignificant decreases in
> rolling resistance (and on some less than smooth surfaces actually
> increases rolling resistance). The recommended air pressure is
> almost always significantly less than people expect. The chart isn't
> the end- all be-all, as different surfaces and types of riding call
> for fine tuning, but it is a much better starting point than what the
> average "knowledgeable" cyclist or bike shop worker--who generally
> overinflates his tires far beyond the point at which any significant
> decrease in rolling resistance is achieved--recommends.

Jan Heine cited this in Bicycle Quarterly earlier this year and
reproduced Berto's chart. Unfortunately there was no discussion as to
how the 15% drop was arrived at as the optimal solution, nor how it was
measured. Carl Fogel has already discussed the difficulties in
measurement when the differences in tire drop are in the thousandths of
an inch range.

> The chart first appeared in Austrian Cyclist March/April of 2004 and
> was reprinted in Bicycle Quarterly Vol. 5 Number 4. I am unsure if
> an internet source exists, but I've found it a valueable reference as
> I set up bikes for a wide variety of riders.

Heine's version of the chart has been posted to a Web site and the URL
was previously given in this thread or another concurrent thread, I
can't recall which.

[carlfogel@comcast.net]

On Fri, 05 Oct 2007 15:51:25 -0500, Tim McNamara
<timmcn@bitstream.net> wrote:

>In article <1191613840.119960.166770@d55g2000hsg.googlegroups. com>,
> Anthony King <trinitybicycles@gmail.com> wrote:
>
>> It looks like the OP found out what almost everyone discovers when
>> they are able to clear their heads of the endlessly repeated
>> falsehood that higher air pressure equals significantly less rolling
>> resistance.
>
>It's relative. The difference between 30 psi and 70 psi is greater than
>the difference between 70 psi and 110 psi. If you look at the old
>rolling resistance measurements from Avocet 20+ years ago, you'll notice
>that the curves flatten quite a bit at higher pressures. It's the same
>phenomenon.
>
>> There is a nice chart made by Frank Berto that determines what air
>> pressure will yield 15% tire drop according to the tire's width and
>> the weight on each wheel of the bike. 15% tire drop is good starting
>> (and usually ending) point, as less yields insignificant decreases in
>> rolling resistance (and on some less than smooth surfaces actually
>> increases rolling resistance). The recommended air pressure is
>> almost always significantly less than people expect. The chart isn't
>> the end- all be-all, as different surfaces and types of riding call
>> for fine tuning, but it is a much better starting point than what the
>> average "knowledgeable" cyclist or bike shop worker--who generally
>> overinflates his tires far beyond the point at which any significant
>> decrease in rolling resistance is achieved--recommends.
>
>Jan Heine cited this in Bicycle Quarterly earlier this year and
>reproduced Berto's chart. Unfortunately there was no discussion as to
>how the 15% drop was arrived at as the optimal solution, nor how it was
>measured. Carl Fogel has already discussed the difficulties in
>measurement when the differences in tire drop are in the thousandths of
>an inch range.
>
>> The chart first appeared in Austrian Cyclist March/April of 2004 and
>> was reprinted in Bicycle Quarterly Vol. 5 Number 4. I am unsure if
>> an internet source exists, but I've found it a valueable reference as
>> I set up bikes for a wide variety of riders.
>
>Heine's version of the chart has been posted to a Web site and the URL
>was previously given in this thread or another concurrent thread, I
>can't recall which.

Dear Tim,

Here's the thread:


http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/433a68b1b62899d0/f6f620148d4ecc9c?lnk=gst&q=carl+%2215%25%22+tire+drop&rnum=1#f6f620148d4ecc9c
or
http://tinyurl.com/yo5gul

Here's the chart:

http://bp1.blogger.com/_d-Yj0VDKhWQ/RnwLUoA9sVI/AAAAAAAAAJ4/225Ym5qYKTo/s1600-h/BQ_berto_inflationgraph.jpg

Briefly, the chart appears to be a theoretical set of perfectly
straight lines, for 6 tire widths (the 7th line is unquestionably a
straight line added with a pencil by a curious owner of a 35 mm tire)
at 9 precise weights for pressures from 30 to 150 psi.

I admire Frank Berto, whose engineering and physics credentials are
even more impressive than his work as a bicycle historian.

But I don't think that the graph reflects actual testing.

How would an actual test work?

First, you measure the actual tire width at each pressure, say every
10 or 15 psi from 30 to 150 psi, meaning 12 measurements with dial
calipers on the part of the tire (as it hangs in mid air) that you
intend to have pressing against the floor during the test.

You can't measure elsewhere on the tire, since it's an inflated rubber
and fabric balloon stretched on a rim--you'll get variations around
the rim.

You have to do it at the pressure that you intend to test because
between 30 and 150 psi, the tire width expands noticeably. Here's the
change that I measured on a nominal 25 mm tire:

psi width

30 0.975
40 0.985 +0.010 !
50 0.992 +0.007
60 0.996 +0.004
70 0.998 +0.002 !
80 1.007 +0.009
90 1.014 +0.007
100 1.018 +0.004
110 1.025 +0.007
120 1.029 +0.004
130 1.034 +0.005
140 1.040 +0.006

The increase from 0.975" to 1.040" means that the tire width itself
increased 6.7%.

You also learn that that measuring the two rubber-coated curved sides
of the tire is trickier than you'd like--try it a few times with some
dial calipers reading in thousandths of an inch. Maybe my individual
measurements were perfectly accurate and reflected the tire creeping
out on the rim in jerks, but it's more likely that it's hard to get
good measurements.

So the base figure of tire width varie 6.7% in an irregular fashion.

Second, how accurate is the air pressure reading? I used Fogel Labs'
finest $25 floor pump, but I wouldn't want to bet on it being accurate
to within 2 psi for a range of 30 to 140 psi. It reads in 2-lb
increments. You could get a laboratory gauge, no doubt, but that
raises the question of how useful the information is going to be for
people who pump their tires up with ordinary gauges.

Third, we have to load the tire. It's no good dangling a handy marked
weight off the handlebar, even if the marking is accurate, because the
weight on the contact patch includes about 6 to 10 pounds from just
the weight of the bare bicycle and there's a surprising leverage
effect if the weight isn't centered over the axle.

So you have to slip a scale under the contact patch and either add and
subtract weights, move them forward or backward, or just leave things
alone and live with whatever the scale says. Maybe the scale is
fearfully accurate, but I wouldn't want to claim that the bathroom
spring scale not-legal-for-trade used at Fogel Labs is accurate to
within a pound. And the load changes a bit when the scale is removed
and the tire is lowered back to the floor.

Fourth, you have to measure the absolute tire drop.

Damned hard to do. In fact, I never even tried because it seemed
ridiculously difficult. I settled for relative drops.

Try to lower a complicated bicycle rig with 80 pounds of weights so
that its inflated front tire _just_ touches the ground like a feather
and then measure that height above the floor as your reference point.

A better approach would be to measure the inflated tire in air from
rim to outside of tire. Then you could lie down on the floor and move
a dial indicator mounted on a floor arm to measure the height of the
rim on the loaded tire above the floor. Subtract and presto!

(Remember, you have to do this for every tire, for every weight, and
for every inflation.)

Come to think of it, that subtraction actually requires a fourth and a
fifth measurement.

Since the difference in measured relative tire drop is only about
0.010" for each 10 psi at typical pressures for a 25 mm tire, it
doesn't seem likely that your results are going to yield
ruler-straight lines, given even tiny +/- errors in each of the five
pieces of data needed for a single measurement. In fact, it seems
likely that the measurement uncertainties would give overall +/-
ranges amounting to 20 psi, rendering the whole exercise pointless,
since being told that some theoretically desirable 15% tire drop will
occur somewhere between 90 and 110 psi isn't going to change many
inflation habits.

The lines on the chart may be best-fit and extrapolation for _very_
small samples, but even that seems unlikely. They look like the ruler
sraight theoretical graph of a theoretical equation.

In any case, it's unlikely that the tire drips in the linear fashion
shown on the graph because the contact patch doesn't change size
directly inflation, as mistakenly simplified theory predicts.

Here's a graph showing the measured results from two sources versus
the predicted change:

http://i17.tinypic.com/2j3jpqc.jpg

When measured, contact patches for ~25 mm 700c tires stubbornly cling
to a preferred middle size, refusing to expand anywhere near as much
as expected when pressure is lowered and refusing to shrink anywhere
near as much as expected when pressure is raised.

It's darned hard to see how the tire drop could stay linear when the
contact patch doesn't.

Cheers,

Carl Fogel

[Tim McNamara]

In article <9cadg3ljgifkkjlep5palshq3chbkagka1@4ax.com>,
carlfogel@comcast.net wrote:

> It's darned hard to see how the tire drop could stay linear when the
> contact patch doesn't.

Indeed, linearity seems relatively rare with the physics of bicycles in
general.

[Anthony King]

I'll leave it to people with more science expertise than I to figure
out all the details, but I'll contend that even if every flaw
suggested is present, Berto's chart is a very good reference. As I
said, it's a starting point. But it's a much, much better starting
point than conventional "high psi is a whole lot faster" wisdom you
get from almost every roadie than causes people to think anything less
than 120 will be slow.

In the end the pay-off for me are the guys who I put on much wider
tires than they've been told can be fast, at psi's they've been told
will be like riding in molasses. They find they don't loose anything
significant when doing their regular rides with their buddies, but
they enjoy the ride a whole lot more. You can see their minds gettin'
blown before your eyes.

Anthony King
----------------------
Trinity Bicycles
www.trinitybicycles.com
437 E. Pioneer Dr. #160
Irving, TX 75061
972.721.7090
Bicycles, parts, and handbuilt wheels for those who value proven and
practical performance.

[Jambo]

"jim beam" <spamvortex@bad.example.net> wrote in message
news:d9idncEf5_1lQ5vanZ2dnUVZ_gydnZ2d@speakeasy.ne t...
> Jambo wrote:
>> "jim beam" <spamvortex@bad.example.net> wrote in message
>> news:NvednVCG6NIAiJ7anZ2dnUVZ_v_inZ2d@speakeasy.ne t...
>>> Jambo wrote:
>>>> "jim beam" <spamvortex@bad.example.net> wrote in message
>>>> news:QNydnS2bmvftXJzanZ2dnUVZ_o3inZ2d@speakeasy.ne t...
>>>>> in answer to your question, no, do not "up" the tension to compensate.
>>>>> rim manufacturers determine spoke tension specs from empirical
>>>>> testing. that means running a rim as part of a loaded wheel with an
>>>>> inflated tire on it.
>>>> Whaddaya know, beamboy borrows from JB's book again...
>>> eh? you're making no sense. moron.
>>
>> Sure I am, and you know it, beamboy.
> love it! invent crap - use it like it's not imaginary! just like your
> materials theory. "modulus is strength to weight", remember? moron.

More like "sikorski" story, and CF noise as damage indicator, and rolled
threads, and your "metarials skool", and CIA black ops classified stuff, and
......

Lying ****tard.

[Michael Press]

In article
<1191641253.922168.183070@w3g2000hsg.googlegroups.c om>,
Anthony King <trinitybicycles@gmail.com> wrote:

> I'll leave it to people with more science expertise than I to figure
> out all the details, but I'll contend that even if every flaw
> suggested is present, Berto's chart is a very good reference. As I
> said, it's a starting point. But it's a much, much better starting
> point than conventional "high psi is a whole lot faster" wisdom you
> get from almost every roadie than causes people to think anything less
> than 120 will be slow.
>
> In the end the pay-off for me are the guys who I put on much wider
> tires than they've been told can be fast, at psi's they've been told
> will be like riding in molasses. They find they don't loose anything
> significant when doing their regular rides with their buddies, but
> they enjoy the ride a whole lot more. You can see their minds gettin'
> blown before your eyes.

I ride 25-32 mm slick tires at 120-90 psi.
Pump them to 120 and let them deflate.

One day a friend had a new bicycle.
A bicycle with wide tires. I took it
for a ride around the block, and it
was like pedaling through mush. Back
on my bicycle and I sailed along on
a summer breeze. Big tires are slow.

He went from slick high pressure tires
to the fat tires because he had lost
so much visual acuity that he could
not dodge all the road hazards to
skinny tires, and _had_ to ride the
fat ones.

--
Michael Press

[jim beam]

Jambo wrote:
> "jim beam" <spamvortex@bad.example.net> wrote in message
> news:d9idncEf5_1lQ5vanZ2dnUVZ_gydnZ2d@speakeasy.ne t...
>> Jambo wrote:
>>> "jim beam" <spamvortex@bad.example.net> wrote in message
>>> news:NvednVCG6NIAiJ7anZ2dnUVZ_v_inZ2d@speakeasy.ne t...
>>>> Jambo wrote:
>>>>> "jim beam" <spamvortex@bad.example.net> wrote in message
>>>>> news:QNydnS2bmvftXJzanZ2dnUVZ_o3inZ2d@speakeasy.ne t...
>>>>>> in answer to your question, no, do not "up" the tension to compensate.
>>>>>> rim manufacturers determine spoke tension specs from empirical
>>>>>> testing. that means running a rim as part of a loaded wheel with an
>>>>>> inflated tire on it.
>>>>> Whaddaya know, beamboy borrows from JB's book again...
>>>> eh? you're making no sense. moron.
>>> Sure I am, and you know it, beamboy.
>> love it! invent crap - use it like it's not imaginary! just like your
>> materials theory. "modulus is strength to weight", remember? moron.
>
> More like "sikorski" story, and CF noise as damage indicator, and rolled
> threads, and your "metarials skool", and CIA black ops classified stuff, and
> .....
>
> Lying ****tard.
>

well, ed, my spelling is not perfect, but it's better than yours.

as for your other drivel, sound /is/ a reliable indicator for cfrp
failure, rolled threads /do/ mitigate fatigue, and many materials [and
their applications] have been classified for /many/ years prior to
general adoption. you'd know this if you bothered to do some homework.
but given that you can't do the trivial homework that would prevent
you making a cock-up like "modulus is strength to weight", i guess
there's not much chance of you seeing the light at this stage. best you
can do is take your meds and try to be happy! moron.

[Anthony King]

On Oct 6, 3:46 am, Michael Press <rub...@pacbell.net> wrote:
> In article
> <1191641253.922168.183...@w3g2000hsg.googlegroups.c om>,
> Anthony King <trinitybicyc...@gmail.com> wrote:
>
> > I'll leave it to people with more science expertise than I to figure
> > out all the details, but I'll contend that even if every flaw
> > suggested is present, Berto's chart is a very good reference. As I
> > said, it's a starting point. But it's a much, much better starting
> > point than conventional "high psi is a whole lot faster" wisdom you
> > get from almost every roadie than causes people to think anything less
> > than 120 will be slow.
>
> > In the end the pay-off for me are the guys who I put on much wider
> > tires than they've been told can be fast, at psi's they've been told
> > will be like riding in molasses. They find they don't loose anything
> > significant when doing their regular rides with their buddies, but
> > they enjoy the ride a whole lot more. You can see their minds gettin'
> > blown before your eyes.
>
> I ride 25-32 mm slick tires at 120-90 psi.
> Pump them to 120 and let them deflate.
>
> One day a friend had a new bicycle.
> A bicycle with wide tires. I took it
> for a ride around the block, and it
> was like pedaling through mush. Back
> on my bicycle and I sailed along on
> a summer breeze. Big tires are slow.
>
> He went from slick high pressure tires
> to the fat tires because he had lost
> so much visual acuity that he could
> not dodge all the road hazards to
> skinny tires, and _had_ to ride the
> fat ones.

All fat tires aren't created the same, just as all skinny one's
aren't, either. The construction of the tire (casing, tread
thickness, etc.) has more a lot to do with speed than a few
millimeters of width. Most large tires are dogs because the
construction is built for durability and flat prevention. Large tires
with light, supple casings and not too thick treads perform very well.

[Michael Press]

In article
<1191687607.977761.70800@19g2000hsx.googlegroups.co m>,
Anthony King <trinitybicycles@gmail.com> wrote:

> On Oct 6, 3:46 am, Michael Press <rub...@pacbell.net> wrote:
> > In article
> > <1191641253.922168.183...@w3g2000hsg.googlegroups.c om>,
> > Anthony King <trinitybicyc...@gmail.com> wrote:
> >
> > > I'll leave it to people with more science expertise than I to figure
> > > out all the details, but I'll contend that even if every flaw
> > > suggested is present, Berto's chart is a very good reference. As I
> > > said, it's a starting point. But it's a much, much better starting
> > > point than conventional "high psi is a whole lot faster" wisdom you
> > > get from almost every roadie than causes people to think anything less
> > > than 120 will be slow.
> >
> > > In the end the pay-off for me are the guys who I put on much wider
> > > tires than they've been told can be fast, at psi's they've been told
> > > will be like riding in molasses. They find they don't loose anything
> > > significant when doing their regular rides with their buddies, but
> > > they enjoy the ride a whole lot more. You can see their minds gettin'
> > > blown before your eyes.
> >
> > I ride 25-32 mm slick tires at 120-90 psi.
> > Pump them to 120 and let them deflate.
> >
> > One day a friend had a new bicycle.
> > A bicycle with wide tires. I took it
> > for a ride around the block, and it
> > was like pedaling through mush. Back
> > on my bicycle and I sailed along on
> > a summer breeze. Big tires are slow.
> >
> > He went from slick high pressure tires
> > to the fat tires because he had lost
> > so much visual acuity that he could
> > not dodge all the road hazards to
> > skinny tires, and _had_ to ride the
> > fat ones.
>
> All fat tires aren't created the same, just as all skinny one's
> aren't, either. The construction of the tire (casing, tread
> thickness, etc.) has more a lot to do with speed than a few
> millimeters of width. Most large tires are dogs because the
> construction is built for durability and flat prevention. Large tires
> with light, supple casings and not too thick treads perform very well.

I will have to take your word for it.
I remain convinced that a tire that
absorbs road shock does so in proportion
to its rolling resistance. If there was
a free lunch, all of us would be riding
fast yet compliant tires.

--
Michael Press

[Ted Bennett]

Michael Press <rubrum@pacbell.net> wrote:

> Anthony King <trinitybicycles@gmail.com> wrote:
>
> > Michael Press <rub...@pacbell.net> wrote:

> > > I ride 25-32 mm slick tires at 120-90 psi.
> > > Pump them to 120 and let them deflate.
> > >
> > > One day a friend had a new bicycle.
> > > A bicycle with wide tires. I took it
> > > for a ride around the block, and it
> > > was like pedaling through mush. Back
> > > on my bicycle and I sailed along on
> > > a summer breeze. Big tires are slow.
> > >
> > > He went from slick high pressure tires
> > > to the fat tires because he had lost
> > > so much visual acuity that he could
> > > not dodge all the road hazards to
> > > skinny tires, and _had_ to ride the
> > > fat ones.
> >
> > All fat tires aren't created the same, just as all skinny one's
> > aren't, either. The construction of the tire (casing, tread
> > thickness, etc.) has more a lot to do with speed than a few
> > millimeters of width. Most large tires are dogs because the
> > construction is built for durability and flat prevention. Large tires
> > with light, supple casings and not too thick treads perform very well.
>
> I will have to take your word for it.
> I remain convinced that a tire that
> absorbs road shock does so in proportion
> to its rolling resistance. If there was
> a free lunch, all of us would be riding
> fast yet compliant tires.

It's another example of the market providing what people want, rather
than what they need. Skinny tires are desirable from the aerodynamic
benefit they provide, and many buyers want to look racy, so they choose
skinny tires. Fatter tires would suit many riders better.

I think you would find it instructive to try various thin-walled larger
volume tires.

--
Ted Bennett

[Ben C]

On 2007-10-06, Michael Press <rubrum@pacbell.net> wrote:
[...]
>> All fat tires aren't created the same, just as all skinny one's
>> aren't, either. The construction of the tire (casing, tread
>> thickness, etc.) has more a lot to do with speed than a few
>> millimeters of width. Most large tires are dogs because the
>> construction is built for durability and flat prevention. Large tires
>> with light, supple casings and not too thick treads perform very well.
>
> I will have to take your word for it.
> I remain convinced that a tire that
> absorbs road shock does so in proportion
> to its rolling resistance.

Why though? They lose energy because of the casing flexing and producing
heat. If you can make the casing supple yet inelastic then you should
expect to lose less energy (at a given pressure and width).

For example a very thin casing would likely be better than a thick one
for RR, although not for puncture resistance.

> If there was a free lunch, all of us would
> be riding fast yet compliant tires.

[Chalo]

Michael Press wrote:
>
> I remain convinced that a tire that
> absorbs road shock does so in proportion
> to its rolling resistance. If there was
> a free lunch, all of us would be riding
> fast yet compliant tires.

I ride frequently with my wife, who inevitably takes the same bike, a
road bike with 700x28 Continental Ultra Sports. She has predictable
riding habits, and she never pedals on even the slightest downhill
stretch. I ride any of several bikes, so by synching my speed with
hers, then coasting and judging my overtaking speed, I can compare the
rolling qualities of my different tires. (There is no obvious
difference in aerodynamics or riding position between most of my
bikes, and the speeds at issue are not high enough for aerodynamics to
be an overwhelming factor anyway.)

Repeated observations among my own bikes show that my Schwalbe Big
Apple 700x60 tires at 35psi outcoast my 700x35 Panaracer Paselas at
80psi. I was quite surprised by this, but after several tries I have
not been able to determine otherwise. The big tires certainly _feel_
slower, though, in the way they handle and respond to bursts of
power.

Chalo

[carlfogel@comcast.net]

On Sat, 06 Oct 2007 16:14:17 -0500, Ben C <spamspam@spam.eggs> wrote:

>On 2007-10-06, Michael Press <rubrum@pacbell.net> wrote:
>[...]
>>> All fat tires aren't created the same, just as all skinny one's
>>> aren't, either. The construction of the tire (casing, tread
>>> thickness, etc.) has more a lot to do with speed than a few
>>> millimeters of width. Most large tires are dogs because the
>>> construction is built for durability and flat prevention. Large tires
>>> with light, supple casings and not too thick treads perform very well.
>>
>> I will have to take your word for it.
>> I remain convinced that a tire that
>> absorbs road shock does so in proportion
>> to its rolling resistance.
>
>Why though? They lose energy because of the casing flexing and producing
>heat. If you can make the casing supple yet inelastic then you should
>expect to lose less energy (at a given pressure and width).
>
>For example a very thin casing would likely be better than a thick one
>for RR, although not for puncture resistance.
>
>> If there was a free lunch, all of us would
>> be riding fast yet compliant tires.

Dear Ben,

Half the fun of browsing the free New York Times archive back in the
1890's is seeing how the same questions and answers occurred to our
great-grandfathers.

As has been previously (1899) discussed:

"Few riders have failed to notice that the most comfort is had with
tires that are a trifle soft, particularly if the road is rough. Yet
the same tire ridden on good roads will give anything but enjoyable
results. It will drag, this hard running increasing in more than due
proportion the better the road becomes. It is interesting to take a
tire and pump it hard, and then, as the air slowly escapes, notice the
change that takes place. It will be uncomfortable riding for a few
day, unless the roads are as level as asphalt. After a little air has
escaped and the riding is done over ordinary roads the tires become
'just right,' neither so hard as to be bumpy nor soft enough to give
too much in going over a crossing. A slightly deflated tire is a
disagreeable reminder occasionally that the rim is very close to the
ground, and ['but' is probably meant here], too, a slightly deflated
tire is not so easily punctured by small stones very frequently ridden
over on macadam roads."


http://query.nytimes.com/gst/abstract.html?res=9E02E0DC133DE633A25752C0A9669D94 689ED7CF

"Small stones" probably means what we call flints, which bite more
easily into tires that are highly inflated to avoid pinch flats.

As a sidelight, I can't find any mention of tire, air, or pressure
gauges for bicycles before 1910 in the NYT archives, nor does Morley
Brothers sell such sissified tools in their 1916 catalogue:

http://www.fixedgeargallery.com/morley/index.htm

I wonder when racers first began to use tire gauges?

Cheers,

Carl Fogel

[Michael Press]

In article
<slrnfgfumn.5ni.spamspam@bowser.marioworld>,
Ben C <spamspam@spam.eggs> wrote:

> On 2007-10-06, Michael Press <rubrum@pacbell.net> wrote:
> [...]
> >> All fat tires aren't created the same, just as all skinny one's
> >> aren't, either. The construction of the tire (casing, tread
> >> thickness, etc.) has more a lot to do with speed than a few
> >> millimeters of width. Most large tires are dogs because the
> >> construction is built for durability and flat prevention. Large tires
> >> with light, supple casings and not too thick treads perform very well.
> >
> > I will have to take your word for it.
> > I remain convinced that a tire that
> > absorbs road shock does so in proportion
> > to its rolling resistance.
>
> Why though? They lose energy because of the casing flexing and producing
> heat. If you can make the casing supple yet inelastic then you should
> expect to lose less energy (at a given pressure and width).
>
> For example a very thin casing would likely be better than a thick one
> for RR, although not for puncture resistance.
>
> > If there was a free lunch, all of us would
> > be riding fast yet compliant tires.

It is an uphill fight against physics with fat(ter) tires.
The larger the radius, the more hoop stress, the stronger
must be the side walls. Stronger side walls mean
less flexible side walls.

--
Michael Press

[carlfogel@comcast.net]

On Sat, 06 Oct 2007 22:40:21 -0000, Chalo <chalo.colina@gmail.com>
wrote:

>Michael Press wrote:
>>
>> I remain convinced that a tire that
>> absorbs road shock does so in proportion
>> to its rolling resistance. If there was
>> a free lunch, all of us would be riding
>> fast yet compliant tires.
>
>I ride frequently with my wife, who inevitably takes the same bike, a
>road bike with 700x28 Continental Ultra Sports. She has predictable
>riding habits, and she never pedals on even the slightest downhill
>stretch. I ride any of several bikes, so by synching my speed with
>hers, then coasting and judging my overtaking speed, I can compare the
>rolling qualities of my different tires. (There is no obvious
>difference in aerodynamics or riding position between most of my
>bikes, and the speeds at issue are not high enough for aerodynamics to
>be an overwhelming factor anyway.)
>
>Repeated observations among my own bikes show that my Schwalbe Big
>Apple 700x60 tires at 35psi outcoast my 700x35 Panaracer Paselas at
>80psi. I was quite surprised by this, but after several tries I have
>not been able to determine otherwise. The big tires certainly _feel_
>slower, though, in the way they handle and respond to bursts of
>power.
>
>Chalo

Dear Chalo,

The results of formal coasting contests in the late 1890's suggest
that more may be going on than we think nowadays. Here's an example
from the free New York Times archive for 1898:

"It is a popular idea that in a coasting contest, other things being
equal, the heaviest man should win. A coasting match took place in
Hartford recently at which this theory was entirely upset. The course
was short, and the grade at the beginning light. One rider weighed 190
pounds and the other was 60 pounds lighter. In the three trials both
men used the same wheels under almost identical conditions. In the
first tiral the lightweight coasted 125 feet, covering the first 100
feet in ten seconds, while the heavier rider was six seconds longer in
going 100 feet, and his distance was 20 feet less. The second trial,
with different equipment, resulted favorably to the heavy man, who
beat his opponent half a second in 100 feet, and was only beaten by
one foot in distance. In the thid trial the spiderwiehgt was again
victorious in time and distance. Both men were supposed to be equally
skilled coasters, and by the rules under which the contest was run
neither could avail himself of any movement to add to his distance."


http://query.nytimes.com/gst/abstract.html?res=9A0CEFDB1438E433A25755C1A9669D94 699ED7CF

Here's a long article on coasting matches from "Outing" magazine in
1898, with some pictures of the tucks used:


http://www.aafla.org/SportsLibrary/Outing/Volume_31/outXXXI06/outXXXI06n.pdf

Cheers,

Carl Fogel

[Anthony King]

On Oct 6, 7:16 pm, Michael Press <rub...@pacbell.net> wrote:
> In article
> <slrnfgfumn.5ni.spams...@bowser.marioworld>,
> Ben C <spams...@spam.eggs> wrote:
>
>
>
> > On 2007-10-06, Michael Press <rub...@pacbell.net> wrote:
> > [...]
> > >> All fat tires aren't created the same, just as all skinny one's
> > >> aren't, either. The construction of the tire (casing, tread
> > >> thickness, etc.) has more a lot to do with speed than a few
> > >> millimeters of width. Most large tires are dogs because the
> > >> construction is built for durability and flat prevention. Large tires
> > >> with light, supple casings and not too thick treads perform very well.
>
> > > I will have to take your word for it.
> > > I remain convinced that a tire that
> > > absorbs road shock does so in proportion
> > > to its rolling resistance.
>
> > Why though? They lose energy because of the casing flexing and producing
> > heat. If you can make the casing supple yet inelastic then you should
> > expect to lose less energy (at a given pressure and width).
>
> > For example a very thin casing would likely be better than a thick one
> > for RR, although not for puncture resistance.
>
> > > If there was a free lunch, all of us would
> > > be riding fast yet compliant tires.
>
> It is an uphill fight against physics with fat(ter) tires.
> The larger the radius, the more hoop stress, the stronger
> must be the side walls. Stronger side walls mean
> less flexible side walls.
>
> --
> Michael Press

Again, your thinking is much too simplistic. Stating that "the more
hoop stress, the stronger must be the side walls. Stronger side walls
mean less flexible side walls" doesn't matter a whit unless the
difference is enough to significantly affect rolling resistance andt
tire manufacturers actually use different sidewalls on tires of
various widths. I'm positive that many manufacturers use the same
sidewall on tires of different widths.

Real world experience and testing that takes tires out of a lab and
off perfectly smooth steel drums repeatedly shows that well made wide
tires are not significantly slower than narrow tires.

Road tests of the Michelin Pro2 Race in 21, 23.5, and 25.5mm (actual
widths) show the wider tire to be fastest. The Clement Del Mondo
Tubular (28mm) tested significantly faster than the Clement Criterium
(21mm). The comfortable Mitsuboshi Trimlines (37mm wide and tested at
55psi) were also faster (though not by a significant margin that the
Clement 21mm tubular and only a hair slower (again, not by a
significat margin) than the Conti Ultra Gatorskin 23mm tire. The
narrow tires were tested at 105 psi.

[Ben C]

On 2007-10-07, Michael Press <rubrum@pacbell.net> wrote:
[...]
> It is an uphill fight against physics with fat(ter) tires.
> The larger the radius, the more hoop stress, the stronger
> must be the side walls. Stronger side walls mean
> less flexible side walls.

Yes more hoop stress, but that's why fatter tyres are rated for lower
pressures. But they also don't need as much pressure as thin ones for
the same RR.

So it's not clear how it all works out. Fat, thin-walled, low-pressure
might have same RR and be more comfortable than thin, thin-walled,
high-pressure.

And stronger only means less flexible if you assume the same material
just made thicker. But in the interests of tackling one thing at a time,
OK.

[jobst.brandt@stanfordalumni.org]

Anthony King writes:

>>>>> All fat tires aren't created the same, just as all skinny one's
>>>>> aren't, either. The construction of the tire (casing, tread
>>>>> thickness, etc.) has more a lot to do with speed than a few
>>>>> millimeters of width. Most large tires are dogs because the
>>>>> construction is built for durability and flat prevention. Large
>>>>> tires with light, supple casings and not too thick treads
>>>>> perform very well.

>>>> I will have to take your word for it. I remain convinced that a
>>>> tire that absorbs road shock does so in proportion to its rolling
>>>> resistance.

>>> Why though? They lose energy because of the casing flexing and
>>> producing heat. If you can make the casing supple yet inelastic
>>> then you should expect to lose less energy (at a given pressure
>>> and width).

>>> For example a very thin casing would likely be better than a thick
>>> one for RR, although not for puncture resistance.

>>>> If there was a free lunch, all of us would be riding fast yet
>>>> compliant tires.

>> It is an uphill fight against physics with fat(ter) tires. The
>> larger the radius, the more hoop stress, the stronger must be the
>> side walls. Stronger side walls mean less flexible side walls.

> Again, your thinking is much too simplistic. Stating that "the more
> hoop stress, the stronger must be the side walls. Stronger side
> walls mean less flexible side walls" doesn't matter a whit unless
> the difference is enough to significantly affect rolling resistance
> and tire manufacturers actually use different sidewalls on tires of
> various widths. I'm positive that many manufacturers use the same
> sidewall on tires of different widths.

> Real world experience and testing that takes tires out of a lab and
> off perfectly smooth steel drums repeatedly shows that well made
> wide tires are not significantly slower than narrow tires.

> Road tests of the Michelin Pro2 Race in 21, 23.5, and 25.5mm (actual
> widths) show the wider tire to be fastest. The Clement Del Mondo
> Tubular (28mm) tested significantly faster than the Clement
> Criterium (21mm). The comfortable Mitsuboshi Trimlines (37mm wide
> and tested at 55psi) were also faster (though not by a significant
> margin that the Clement 21mm tubular and only a hair slower (again,
> not by a significant margin) than the Conti Ultra Gatorskin 23mm
> tire. The narrow tires were tested at 105 psi.

http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html
http://www.sheldonbrown.com/brandt/rim-support.html
http://www.sheldonbrown.com/brandt/rolling-resistance.html

Rim forces that tend to spread the beads apart are dependent on casing
angle with which the tire departs from the rim and inflation pressure.
Tire blow-off from the rim is dependent on casing angle and bead
inside spacing that bot furnish separating force.

Jobst Brandt

[Michael Press]

In article
<1191731650.604268.289930@50g2000hsm.googlegroups.c om>,
Anthony King <trinitybicycles@gmail.com> wrote:

> On Oct 6, 7:16 pm, Michael Press <rub...@pacbell.net> wrote:
> > In article
> > <slrnfgfumn.5ni.spams...@bowser.marioworld>,
> > Ben C <spams...@spam.eggs> wrote:
> >
> >
> >
> > > On 2007-10-06, Michael Press <rub...@pacbell.net> wrote:
> > > [...]
> > > >> All fat tires aren't created the same, just as all skinny one's
> > > >> aren't, either. The construction of the tire (casing, tread
> > > >> thickness, etc.) has more a lot to do with speed than a few
> > > >> millimeters of width. Most large tires are dogs because the
> > > >> construction is built for durability and flat prevention. Large tires
> > > >> with light, supple casings and not too thick treads perform very well.
> >
> > > > I will have to take your word for it.
> > > > I remain convinced that a tire that
> > > > absorbs road shock does so in proportion
> > > > to its rolling resistance.
> >
> > > Why though? They lose energy because of the casing flexing and producing
> > > heat. If you can make the casing supple yet inelastic then you should
> > > expect to lose less energy (at a given pressure and width).
> >
> > > For example a very thin casing would likely be better than a thick one
> > > for RR, although not for puncture resistance.
> >
> > > > If there was a free lunch, all of us would
> > > > be riding fast yet compliant tires.
> >
> > It is an uphill fight against physics with fat(ter) tires.
> > The larger the radius, the more hoop stress, the stronger
> > must be the side walls. Stronger side walls mean
> > less flexible side walls.
>
> Again, your thinking is much too simplistic. Stating that "the more
> hoop stress, the stronger must be the side walls. Stronger side walls
> mean less flexible side walls" doesn't matter a whit unless the
> difference is enough to significantly affect rolling resistance andt
> tire manufacturers actually use different sidewalls on tires of
> various widths. I'm positive that many manufacturers use the same
> sidewall on tires of different widths.

Are you? Quote some.

The Avocet Fasgrip has 127 tpi side walls on 23-25 mm tires;
67 tpi side walls on 28-32 mm tires.

>
> Real world experience and testing that takes tires out of a lab and
> off perfectly smooth steel drums repeatedly shows that well made wide
> tires are not significantly slower than narrow tires.

My limited real world experience is otherwise.

> Road tests of the Michelin Pro2 Race in 21, 23.5, and 25.5mm (actual
> widths) show the wider tire to be fastest.

Not that I know of.

> The Clement Del Mondo
> Tubular (28mm) tested significantly faster than the Clement Criterium
> (21mm). The comfortable Mitsuboshi Trimlines (37mm wide and tested at
> 55psi) were also faster (though not by a significant margin that the
> Clement 21mm tubular and only a hair slower (again, not by a
> significat margin) than the Conti Ultra Gatorskin 23mm tire. The
> narrow tires were tested at 105 psi.

Fascinating.

--
Michael Press

[jobst.brandt@stanfordalumni.org]

Ben C? writes:

>> It is an uphill fight against physics with fat(ter) tires. The
>> larger the radius, the more hoop stress, the stronger must be the
>> side walls. Stronger side walls mean less flexible side walls.

> Yes more hoop stress, but that's why fatter tyres are rated for
> lower pressures. But they also don't need as much pressure as thin
> ones for the same RR.

That is only so if the casing and tread rubber are similarly pliable
(tread thickness).

> So it's not clear how it all works out. Fat, thin-walled,
> low-pressure might have same RR and be more comfortable than thin,
> thin-walled, high-pressure.

It arises from the amount of flexing the tread, casing and inner tube
make with road contact. They all have hysteresis, a quality by which
rebound is not the same as compression force.

http://mw1.merriam-webster.com/dictionary/hysteresis

> And stronger only means less flexible if you assume the same
> material just made thicker. But in the interests of tackling one
> thing at a time, OK.

"Stronger" can also be achieved by using better materials, such as
rayon or silk casing cords. However, most (but not all) fatter tires
also have thicker tread and sidewall protection.

Jobst Brandt

[Tom \Johnny Sunset\ Sherman]

Michael Press of Possum Lodge wrote:
> ...
> The Avocet Fasgrip has 127 tpi side walls on 23-25 mm tires;
> 67 tpi side walls on 28-32 mm tires.

And 67-tpi on my 44 mm wide Avocet tires.

--
Tom Sherman - Holstein-Friesland Bovinia
A Real Cyclist [TM] keeps at least one bicycle in the bedroom.

--
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