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Why does low pressure cost mileage?
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RichD
Feb 2, 2012, 9:34:15 PM2/2/12
to
Low air pressure in tires retards fuel milege, but why?
The obvious answer is, greater friction. But even though
the tire is flatter, still it rolls, there's no relative movement
between the pavement and tire, hence no sliding friction.
So where and how do the losses occur?
--
Rich
The obvious answer is, greater friction. But even though
the tire is flatter, still it rolls, there's no relative movement
between the pavement and tire, hence no sliding friction.
So where and how do the losses occur?
--
Rich
DirtRoadie
Feb 2, 2012, 10:00:12 PM2/2/12
to
the fabric and rubber.
http://en.wikipedia.org/wiki/Hysteresis#Hysteresis_in_mechanics
DR
Tom Ace
Feb 2, 2012, 10:03:39 PM2/2/12
to
a portion of which is lost to heat in the tire (i.e. not returned as
mechanical energy when the tire springs back). See
http://en.wikipedia.org/wiki/Hysteresis_loss#Elastic_hysteresis
and
http://draco.nac.uci.edu/rbfaq/FAQ/8b.14.html
Tom Ace
kolldata
Feb 2, 2012, 10:05:14 PM2/2/12
to
Darwin123
Feb 3, 2012, 4:55:22 PM2/3/12
to
bending.
When you bend a material, some of the kinetic energy is turned
into other forms of energy. you create some elastic potential energy
stored in the strain field of the material. However, you also create
thermal internal energy stored in the entropy of the material.
When the pressure is low, the tire material bends because the
shape of the tire is changing. As the tire rolls, the flat part of the
tire pressed against the ground moves around the rim. In order for the
flat part to move around the rim, the rubber of the tire must bend. In
rubber, most of the bending is inelastic. So the kinetic energy is
turned to thermal internal energy.
The inelastic bending is also associated with hysteresis as well
as friction. The rubber becomes cracked and dry with greater use. So
the rubber degrades with time of use.
Frank Krygowski
Feb 3, 2012, 4:58:03 PM2/3/12
to
On Feb 2, 9:34 pm, RichD <r_delaney2...@yahoo.com> wrote:
think if you lowered one of your car's tires to, say, 20 psi and drove
on the freeway for a mile, you could easily detect that the tire was
hotter, indicating that it's sucking up energy. Admittedly, I don't
plan to try that test myself.
Think about dribbling a basketball. If the ball's soft, it doesn't
rebound nearly as well. Obviously more energy is lost. It's probably
going into the rubber.
Also, I think there would be more relative movement between the
pavement and tire, due to a sort of scrubbing action. Tires that are
consistently run with pressure that's too low tend to wear faster,
mostly toward the edges.
What seems to be different about bikes and cars is that, AFAIK, a
car's gas mileage doesn't decrease if you have tire pressure too high,
at least within reasonable limits. But a bike can take more energy to
move if you have too much pressure. The difference seems to be
related to lack of mechanical suspension on a bike; the bike tire is
typically the only suspension, and too much pressure makes the bike a
rigid, unsuspended vehicle.
- Frank Krygowski
gpsman
Feb 3, 2012, 6:19:57 PM2/3/12
to
On Feb 3, 4:58 pm, Frank Krygowski <frkry...@gmail.com> wrote:
>
> What seems to be different about bikes and cars is that, AFAIK, a
> car's gas mileage doesn't decrease if you have tire pressure too high,
> at least within reasonable limits. But a bike can take more energy to
> move if you have too much pressure.
I did not know more tire pressure = more resistance.
>
> What seems to be different about bikes and cars is that, AFAIK, a
> car's gas mileage doesn't decrease if you have tire pressure too high,
> at least within reasonable limits. But a bike can take more energy to
> move if you have too much pressure.
> The difference seems to be
> related to lack of mechanical suspension on a bike; the bike tire is
> typically the only suspension, and too much pressure makes the bike a
> rigid, unsuspended vehicle.
what you're talking about.
-----
- gpsman
James
Feb 3, 2012, 7:39:27 PM2/3/12
to
On Feb 4, 10:19 am, gpsman <gps...@driversmail.com> wrote:
> On Feb 3, 4:58 pm, Frank Krygowski <frkry...@gmail.com> wrote:
>
>
>
> > What seems to be different about bikes and cars is that, AFAIK, a
> > car's gas mileage doesn't decrease if you have tire pressure too high,
> > at least within reasonable limits. But a bike can take more energy to
> > move if you have too much pressure.
>
> I did not know more tire pressure = more resistance.
Generally, more pressure reduces rolling resistance.
> On Feb 3, 4:58 pm, Frank Krygowski <frkry...@gmail.com> wrote:
>
>
>
> > What seems to be different about bikes and cars is that, AFAIK, a
> > car's gas mileage doesn't decrease if you have tire pressure too high,
> > at least within reasonable limits. But a bike can take more energy to
> > move if you have too much pressure.
>
> I did not know more tire pressure = more resistance.
It is possible that above some pressure, and depending on the road
surface roughness, that more vertical energy is transmitted to the
rider, who absorbs vibration energy and does not return it to forward
momentum.
> > The difference seems to be
> > related to lack of mechanical suspension on a bike; the bike tire is
> > typically the only suspension, and too much pressure makes the bike a
> > rigid, unsuspended vehicle.
>
> From here, the difference seems to be your ability to imagine you know
> what you're talking about.
in this field due to the variability of roads, riders and conditions,
that make measurements of this kind difficult. We are only talking
very small amounts of energy. Maybe 1% of the riders output? (3W in
300W to hazard a guess.)
Tyre rolling resistance tests are performed on a smooth steel drum, so
that the manufacturers can have a standardised test and end users can
compare, however few of us ride on smooth steel drums or on boards.
--
JS.
thirty-six
Feb 3, 2012, 8:06:33 PM2/3/12
to
On Feb 3, 2:34 am, RichD <r_delaney2...@yahoo.com> wrote:
> Low air pressure in tires retards fuel milege, but why?
larger perimeter of deformation of the tyre and more abrupt change of
> Low air pressure in tires retards fuel milege, but why?
angle lead to higher hysteresis loses which are found as heat.
>
> The obvious answer is, greater friction. But even though
> the tire is flatter, still it rolls, there's no relative movement
> between the pavement and tire, hence no sliding friction.
>
> So where and how do the losses occur?
In the threads of the carcass, in the latex or rubber between the
> The obvious answer is, greater friction. But even though
> the tire is flatter, still it rolls, there's no relative movement
> between the pavement and tire, hence no sliding friction.
>
> So where and how do the losses occur?
threads, in the rubber tread and any sales bits and bobs the
manufacturers can reach a bit deeper into your wallet with.
thirty-six
Feb 3, 2012, 8:13:11 PM2/3/12
to
learnt to stick a plaster on an inner tube" and "We woz so clever that
our poor tyre gluing was caused by our brakes.". Time for bed.
DirtRoadie
Feb 4, 2012, 12:37:50 AM2/4/12
to
On Feb 3, 2:58 pm, Frank Krygowski <frkry...@gmail.com> wrote:
> What seems to be different about bikes and cars is that, AFAIK, a
> car's gas mileage doesn't decrease if you have tire pressure too high,
> at least within reasonable limits. But a bike can take more energy to
> move if you have too much pressure. The difference seems to be
> related to lack of mechanical suspension on a bike; the bike tire is
> typically the only suspension, and too much pressure makes the bike a
> rigid, unsuspended vehicle.
>
> - Frank Krygowski
Frank, why don't you think about this a little bit and see if you
> What seems to be different about bikes and cars is that, AFAIK, a
> car's gas mileage doesn't decrease if you have tire pressure too high,
> at least within reasonable limits. But a bike can take more energy to
> move if you have too much pressure. The difference seems to be
> related to lack of mechanical suspension on a bike; the bike tire is
> typically the only suspension, and too much pressure makes the bike a
> rigid, unsuspended vehicle.
>
> - Frank Krygowski
might want to write something more complete and accurate.
Unless, of course AFAYK there could be NO condition under which an
automobile might suffer greater decreased mileage from too high a
pressure.
Hint: Ever used a wheelbarrow?
DR
Frank Krygowski
Feb 4, 2012, 12:44:31 AM2/4/12
to
On Feb 3, 6:19 pm, gpsman <gps...@driversmail.com> wrote:
> On Feb 3, 4:58 pm, Frank Krygowski <frkry...@gmail.com> wrote:
>
>
>
> > What seems to be different about bikes and cars is that, AFAIK, a
> > car's gas mileage doesn't decrease if you have tire pressure too high,
> > at least within reasonable limits. But a bike can take more energy to
> > move if you have too much pressure.
>
> I did not know more tire pressure = more resistance.
It depends on the relative roughness of the road surface, and on the
> On Feb 3, 4:58 pm, Frank Krygowski <frkry...@gmail.com> wrote:
>
>
>
> > What seems to be different about bikes and cars is that, AFAIK, a
> > car's gas mileage doesn't decrease if you have tire pressure too high,
> > at least within reasonable limits. But a bike can take more energy to
> > move if you have too much pressure.
>
> I did not know more tire pressure = more resistance.
relative magnitude of suspension losses vs. hysteresis losses in the
rubber. On a board track, extremely high tire pressures are better;
but on a board track, suspension isn't needed.
For the opposite extreme, try riding a rigid mountain bike on gravel
about 3" diameter, as I've done on an abandoned railroad bed. Even 50
psi made it very difficult to ride. Lowering tire pressure to just
prevent pinch flats made it much easier.
Most roads are between those extremes. But if the road has any
roughness at all, there will be some tire pressure above which power
requirements will be greater due to greater suspension losses. If that
weren't true, we'd dispense with the air and go back to solid rubber
tires, as hard as possible.
> > The difference seems to be
> > related to lack of mechanical suspension on a bike; the bike tire is
> > typically the only suspension, and too much pressure makes the bike a
> > rigid, unsuspended vehicle.
>
> From here, the difference seems to be your ability to imagine you know
> what you're talking about.
capabilities. But take heart. You can still learn.
- Frank Krygowski
gpsman
Feb 4, 2012, 12:58:52 AM2/4/12
to
On Feb 4, 12:44 am, Frank Krygowski <frkry...@gmail.com> wrote:
> On Feb 3, 6:19 pm, gpsman <gps...@driversmail.com> wrote:
>
> > I did not know more tire pressure = more resistance.
>
> On Feb 3, 6:19 pm, gpsman <gps...@driversmail.com> wrote:
>
> > I did not know more tire pressure = more resistance.
>
> if the road has any
> roughness at all, there will be some tire pressure above which power
> requirements will be greater due to greater suspension losses. If that
> weren't true, we'd dispense with the air and go back to solid rubber
> tires, as hard as possible.
False premise; fails to consider weight. We needn't delve into the
> roughness at all, there will be some tire pressure above which power
> requirements will be greater due to greater suspension losses. If that
> weren't true, we'd dispense with the air and go back to solid rubber
> tires, as hard as possible.
relative "roughness" of road surfaces.
> You can still learn.
I'm sure there's something you can teach me, but this ain't it.
-----
- gpsman
Chalo
Feb 4, 2012, 4:51:06 AM2/4/12
to
gpsman wrote:
When you inflate tires hard enough to yield a harsh, jarring ride,
where do you think the energy required to jar you comes from? Shaking
a couple hundred pounds of sloppy flesh and bone can waste far more
energy than you can dissipate in tread rubber.
Chalo
>
> Frank Krygowski wrote:
> >
> > What seems to be different about bikes and cars is that, AFAIK, a
> > car's gas mileage doesn't decrease if you have tire pressure too high,
> > at least within reasonable limits. But a bike can take more energy to
> > move if you have too much pressure.
>
> I did not know more tire pressure = more resistance.
>
> > The difference seems to be
> > related to lack of mechanical suspension on a bike; the bike tire is
> > typically the only suspension, and too much pressure makes the bike a
> > rigid, unsuspended vehicle.
>
> From here, the difference seems to be your ability to imagine you know
> what you're talking about.
No, it's you.
> Frank Krygowski wrote:
> >
> > What seems to be different about bikes and cars is that, AFAIK, a
> > car's gas mileage doesn't decrease if you have tire pressure too high,
> > at least within reasonable limits. But a bike can take more energy to
> > move if you have too much pressure.
>
> I did not know more tire pressure = more resistance.
>
> > The difference seems to be
> > related to lack of mechanical suspension on a bike; the bike tire is
> > typically the only suspension, and too much pressure makes the bike a
> > rigid, unsuspended vehicle.
>
> From here, the difference seems to be your ability to imagine you know
> what you're talking about.
When you inflate tires hard enough to yield a harsh, jarring ride,
where do you think the energy required to jar you comes from? Shaking
a couple hundred pounds of sloppy flesh and bone can waste far more
energy than you can dissipate in tread rubber.
Chalo
kolldata
Feb 4, 2012, 10:02:22 AM2/4/12
to
hoop snakes.
less pressure equals greater contact surface
greater contact surface and less pressure deforms designed contact
surface
now surfaceS
surfaceS change shape=loss
surfaceS grip road channels as small road walls, opposing pothole
walls, deflect travel direction continuously
and on
low pressure morphs a designed solid surface into a road sponge
I cant believe I wrote this
less pressure equals greater contact surface
greater contact surface and less pressure deforms designed contact
surface
now surfaceS
surfaceS change shape=loss
surfaceS grip road channels as small road walls, opposing pothole
walls, deflect travel direction continuously
and on
low pressure morphs a designed solid surface into a road sponge
I cant believe I wrote this
gpsman
Feb 4, 2012, 10:42:40 AM2/4/12
to
On Feb 4, 4:51 am, Chalo <chalo.col...@gmail.com> wrote:
>
> When you inflate tires hard enough to yield a harsh, jarring ride,
> where do you think the energy required to jar you comes from? Shaking
> a couple hundred pounds of sloppy flesh and bone can waste far more
> energy than you can dissipate in tread rubber.
Ipse dixit.
>
> When you inflate tires hard enough to yield a harsh, jarring ride,
> where do you think the energy required to jar you comes from? Shaking
> a couple hundred pounds of sloppy flesh and bone can waste far more
> energy than you can dissipate in tread rubber.
-----
- gpsman
Frank Krygowski
Feb 4, 2012, 10:53:01 PM2/4/12
to
On Feb 4, 12:58 am, gpsman <gps...@driversmail.com> wrote:
> On Feb 4, 12:44 am, Frank Krygowski <frkry...@gmail.com> wrote:
>
> > On Feb 3, 6:19 pm, gpsman <gps...@driversmail.com> wrote:
>
> > > I did not know more tire pressure = more resistance.
>
> > if the road has any
> > roughness at all, there will be some tire pressure above which power
> > requirements will be greater due to greater suspension losses. If that
> > weren't true, we'd dispense with the air and go back to solid rubber
> > tires, as hard as possible.
>
> False premise; fails to consider weight.
Explain, please. If you mean the weight of the tire itself, _surely_
> On Feb 4, 12:44 am, Frank Krygowski <frkry...@gmail.com> wrote:
>
> > On Feb 3, 6:19 pm, gpsman <gps...@driversmail.com> wrote:
>
> > > I did not know more tire pressure = more resistance.
>
> > if the road has any
> > roughness at all, there will be some tire pressure above which power
> > requirements will be greater due to greater suspension losses. If that
> > weren't true, we'd dispense with the air and go back to solid rubber
> > tires, as hard as possible.
>
> False premise; fails to consider weight.
you don't believe that's the reason pneumatic tires replaced solid
rubber, do you?
Since you seem to be unfamiliar with this topic, let me add a bit of
explanation. What I'm calling "suspension loss" is the energy
converted into heat by internal friction, due to the shaking of
(primarily) the rider's body. If the road is not perfectly smooth -
and none are - that jostling of the body costs energy. It slows you
down.
Anything that suspends the body (and bike) from jostling reduces that
energy. However, if it's done poorly enough - say, by thick tires that
flex a lot - it's possible to get excessive energy loss by hysteresis
within the tire itself. You want enough tire flex to reduce
suspension loss, without incurring excess hysteresis loss in the tire.
> We needn't delve into the
> relative "roughness" of road surfaces.
If you don't want to understand the mechanics of a bicycle's rolling
resistance, you can skip all of this.
> > You can still learn.
>
> I'm sure there's something you can teach me, but this ain't it.
- Frank Krygowski
Dan O
Feb 5, 2012, 12:01:11 AM2/5/12
to
On Feb 4, 7:53 pm, Frank Krygowski <frkry...@gmail.com> wrote:
> On Feb 4, 12:58 am, gpsman <gps...@driversmail.com> wrote:
>
> > On Feb 4, 12:44 am, Frank Krygowski <frkry...@gmail.com> wrote:
>
<snip>
> On Feb 4, 12:58 am, gpsman <gps...@driversmail.com> wrote:
>
> > On Feb 4, 12:44 am, Frank Krygowski <frkry...@gmail.com> wrote:
>
>
> > > You can still learn.
>
> > I'm sure there's something you can teach me, but this ain't it.
>
> Ah well. Not everyone can learn everything.
>
gpsman
Feb 6, 2012, 9:13:12 AM2/6/12
to
On Feb 4, 10:53 pm, Frank Krygowski <frkry...@gmail.com> wrote:
> On Feb 4, 12:58 am, gpsman <gps...@driversmail.com> wrote:
>
> > On Feb 4, 12:44 am, Frank Krygowski <frkry...@gmail.com> wrote:
>
> > > On Feb 3, 6:19 pm, gpsman <gps...@driversmail.com> wrote:
>
> > > > I did not know more tire pressure = more resistance.
>
> > > if the road has any
> > > roughness at all, there will be some tire pressure above which power
> > > requirements will be greater due to greater suspension losses. If that
> > > weren't true, we'd dispense with the air and go back to solid rubber
> > > tires, as hard as possible.
>
> > False premise; fails to consider weight.
>
> Explain, please.
Your premise is false: Single cause fallacy.
> On Feb 4, 12:58 am, gpsman <gps...@driversmail.com> wrote:
>
> > On Feb 4, 12:44 am, Frank Krygowski <frkry...@gmail.com> wrote:
>
> > > On Feb 3, 6:19 pm, gpsman <gps...@driversmail.com> wrote:
>
> > > > I did not know more tire pressure = more resistance.
>
> > > if the road has any
> > > roughness at all, there will be some tire pressure above which power
> > > requirements will be greater due to greater suspension losses. If that
> > > weren't true, we'd dispense with the air and go back to solid rubber
> > > tires, as hard as possible.
>
> > False premise; fails to consider weight.
>
> Explain, please.
> If you mean the weight of the tire itself, _surely_
> you don't believe that's the reason pneumatic tires replaced solid
> rubber, do you?
> If you don't want to understand the mechanics of a bicycle's rolling
> resistance, you can skip all of this.
maybe I'll have a chance...
-----
- gpsman
Frank Krygowski
Feb 6, 2012, 11:54:23 AM2/6/12
to
losses, hysteresis losses and power requirements, give it. So far,
you've said nothing meaningful. Quit sniping from the sidelines.
In fact, you were confused right out of the gate. When I said "But a
bike can take more energy to move if you have too much pressure" you
seemed to misinterpret that as "more tire pressure _always_ yields
more resistance." At least, that's what your statement "I did not
know more tire pressure = more resistance" seems to say.
- Frank Krygowski
gpsman
Feb 6, 2012, 12:20:54 PM2/6/12
to
On Feb 6, 11:54 am, Frank Krygowski <frkry...@gmail.com> wrote:
> On Feb 6, 9:13 am, gpsman <gps...@driversmail.com> wrote:
>
>
>
> > On Feb 4, 10:53 pm, Frank Krygowski <frkry...@gmail.com> wrote:
>
> > > On Feb 4, 12:58 am, gpsman <gps...@driversmail.com> wrote:
>
> > > > On Feb 4, 12:44 am, Frank Krygowski <frkry...@gmail.com> wrote:
>
> > > > > On Feb 3, 6:19 pm, gpsman <gps...@driversmail.com> wrote:
>
> > > > > > I did not know more tire pressure = more resistance.
>
> > > > > if the road has any
> > > > > roughness at all, there will be some tire pressure above which power
> > > > > requirements will be greater due to greater suspension losses. If that
> > > > > weren't true, we'd dispense with the air and go back to solid rubber
> > > > > tires, as hard as possible.
>
> > > > False premise; fails to consider weight.
>
> > > Explain, please.
>
> > Your premise is false: Single cause fallacy.
>
> > > If you mean the weight of the tire itself, _surely_
> > > you don't believe that's the reason pneumatic tires replaced solid
> > > rubber, do you?
>
> > No. You infer fallaciously as well.
>
> > > If you don't want to understand the mechanics of a bicycle's rolling
> > > resistance, you can skip all of this.
>
> > Demonstrate your understanding by quantifying your assertions. Then,
> > maybe I'll have a chance...
>
> You first, gpsman.
Red herring. Thanks for playing.
> On Feb 6, 9:13 am, gpsman <gps...@driversmail.com> wrote:
>
>
>
> > On Feb 4, 10:53 pm, Frank Krygowski <frkry...@gmail.com> wrote:
>
> > > On Feb 4, 12:58 am, gpsman <gps...@driversmail.com> wrote:
>
> > > > On Feb 4, 12:44 am, Frank Krygowski <frkry...@gmail.com> wrote:
>
> > > > > On Feb 3, 6:19 pm, gpsman <gps...@driversmail.com> wrote:
>
> > > > > > I did not know more tire pressure = more resistance.
>
> > > > > if the road has any
> > > > > roughness at all, there will be some tire pressure above which power
> > > > > requirements will be greater due to greater suspension losses. If that
> > > > > weren't true, we'd dispense with the air and go back to solid rubber
> > > > > tires, as hard as possible.
>
> > > > False premise; fails to consider weight.
>
> > > Explain, please.
>
> > Your premise is false: Single cause fallacy.
>
> > > If you mean the weight of the tire itself, _surely_
> > > you don't believe that's the reason pneumatic tires replaced solid
> > > rubber, do you?
>
> > No. You infer fallaciously as well.
>
> > > If you don't want to understand the mechanics of a bicycle's rolling
> > > resistance, you can skip all of this.
>
> > Demonstrate your understanding by quantifying your assertions. Then,
> > maybe I'll have a chance...
>
> You first, gpsman.
-----
- gpsman
Chalo
Feb 6, 2012, 2:51:13 PM2/6/12
to
gpsman wrote:
approximates an underinflated tire in terms of its coefficient of
restitution. Then try to dribble a basketball-sized rump roast
(thawed), which approximates a human body in terms of its coefficient
of restitution. Which one absorbs a larger share of the kinetic
energy of its fall to the ground? Does the meat bounce back higher
when dropped directly onto the floor, or when dropped onto the
basketball?
The tire's suspension characteristics can save more energy losses than
they can possibly incur, even on comparatively smooth surfaces.
That's why Dr. Dunlop's business prospered so marvelously.
The tire pressure at which rubber losses exceed suspension losses
depends on a lot of factors including surface unevenness, tire width
and construction, road speed, riding style, etc, etc. But it's both
observable and broadly acknowledged that for any given set of
conditions, there is a point at which higher tire pressure results in
less, not more, speed per effort.
Chalo
>
> Chalo wrote:
> >
> > When you inflate tires hard enough to yield a harsh, jarring ride,
> > where do you think the energy required to jar you comes from? Shaking
> > a couple hundred pounds of sloppy flesh and bone can waste far more
> > energy than you can dissipate in tread rubber.
>
> Ipse dixit.
Here's an experiment you can do. Dribble a basketball. which
> Chalo wrote:
> >
> > When you inflate tires hard enough to yield a harsh, jarring ride,
> > where do you think the energy required to jar you comes from? Shaking
> > a couple hundred pounds of sloppy flesh and bone can waste far more
> > energy than you can dissipate in tread rubber.
>
> Ipse dixit.
approximates an underinflated tire in terms of its coefficient of
restitution. Then try to dribble a basketball-sized rump roast
(thawed), which approximates a human body in terms of its coefficient
of restitution. Which one absorbs a larger share of the kinetic
energy of its fall to the ground? Does the meat bounce back higher
when dropped directly onto the floor, or when dropped onto the
basketball?
The tire's suspension characteristics can save more energy losses than
they can possibly incur, even on comparatively smooth surfaces.
That's why Dr. Dunlop's business prospered so marvelously.
The tire pressure at which rubber losses exceed suspension losses
depends on a lot of factors including surface unevenness, tire width
and construction, road speed, riding style, etc, etc. But it's both
observable and broadly acknowledged that for any given set of
conditions, there is a point at which higher tire pressure results in
less, not more, speed per effort.
Chalo
AMuzi
Feb 6, 2012, 11:26:52 PM2/6/12
to
above which resistance increases for any given section tire.
So, excessively low or high pressures should probably be
avoided but the actual numbers vary from one setup to another.
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
jim beam
Feb 7, 2012, 12:03:16 AM2/7/12
to
truth is, there ain't much krygowski can teach anyone. the guy's not
just a fraud and disgrace to his faculty, but an ignorant fraud to boot.
http://www.cyclebanter.com/showthread.php?t=215977
"The engineering ignorance of Frank Krygowski" has become a meme - and
has been running for many years over on r.b.t, without my assistance!
--
nomina rutrum rutrum
Frank Krygowski
Feb 7, 2012, 11:10:17 AM2/7/12
to
certain percentage deflection under load - something like 15% of tire
diameter.
- Frank Krygowski
(PeteCresswell)
Feb 7, 2012, 11:33:46 AM2/7/12
to
Per gpsman:
Taking it to the absurd, my 55-55's roll much better over rough
ground at 35 psi than they do at 60 psi.
OTOH, running the same comparison on smooth blacktop, 60 psi
rolls easier.
--
Pete Cresswell
>I did not know more tire pressure = more resistance.
I'd think it depends on the surface being ridden on.
Taking it to the absurd, my 55-55's roll much better over rough
ground at 35 psi than they do at 60 psi.
OTOH, running the same comparison on smooth blacktop, 60 psi
rolls easier.
--
Pete Cresswell
carl...@comcast.net
Feb 7, 2012, 12:02:45 PM2/7/12
to
For what it's worth . . .
Here's a fairly short thread with actual test data on measuring drop
versus pressure and replies with more comments about various tests,
including Jan Heine:
http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/433a68b1b62899d0/b8ba9253cce51d67?#b8ba9253cce51d67
If you browse far enough, you'll find that the changes for a tire drop
of 15% are so tiny that they can hardly be measured for ordinary
pressure changes.
On the test 700c tire, a 15% drop (as opposed to 10% or 20% drop)
covered a huge range of roughly 40 psi, 70 psi to 110 psi, and a tiny
range of drop from 0.126" to 0.174", roughly 0.050 inches, less than a
sixteenth of an inch.
There's a link to a suspiciously smooth graph that doesn't seem to
show the predicted divergence from linear changes as tire pressure
increases or decreases from a sweet spot:
http://bp1.blogger.com/_d-Yj0VDKhWQ/RnwLUoA9sVI/AAAAAAAAAJ4/225Ym5qYKTo/s1600-h/BQ_berto_inflationgraph.jpg
Briefly, tires don't actually work in the over-simplified way that we
often assume in which contact patch area increases and decreases
linearly with pressure. The contact patch stubbornly refuses to expand
as much as expected when pressure is reduced, and it's just as
reluctant to contract when pressure is increased.
The reason is that the pressure is not even on the contact patch, due
to the sidewall acting somewhat like a scissors jack when its curved
shape distorts.
At low pressures, a halo of high pressure forms around the edges of
the contact patch.
At high pressures, a halo of low pressure forms around the edges.
Only in a narrow range of medium pressures does the contact patch
spread out at an even pressure to match our expectations.
Cheers,
Carl Fogel
Noone
Feb 7, 2012, 12:05:45 PM2/7/12
to
"Frank Krygowski" <frkr...@gmail.com> wrote in message
news:d794c26c-e6ce-44c6...@a15g2000yqf.googlegroups.com...
.+^+.+^+.+^+.+^+.+^+.+^+.+^+.+^+.+^+.+^+.+^+.+^+.
Might you mean 15% of tire sidewall height?
news:d794c26c-e6ce-44c6...@a15g2000yqf.googlegroups.com...
Might you mean 15% of tire sidewall height?
Steve W.
Feb 7, 2012, 12:56:43 PM2/7/12
to
RichD wrote:
> Low air pressure in tires retards fuel milege, but why?
>
> Low air pressure in tires retards fuel milege, but why?
>
> The obvious answer is, greater friction. But even though
> the tire is flatter, still it rolls, there's no relative movement
> between the pavement and tire, hence no sliding friction.
>
> So where and how do the losses occur?
>
> --
> the tire is flatter, still it rolls, there's no relative movement
> between the pavement and tire, hence no sliding friction.
>
> So where and how do the losses occur?
>
> Rich
Higher friction which generates more heat in the tire and makes it get
even lower. The larger contact patch takes more
power to rotate.
Reduced tire diameter from the lowering air pressure means the tire has
to turn more revolutions per mile at a given speed.
One tire lower than another on the driving axle also means more heat
generated from friction inside the differential and transmission due to
the uneven tire sizes causing torque wrap.
The increased work the engine has to do to overcome all the above causes
you to get lower MPG than tires inflated to the correct pressure.
This is why most of the super mileage hybrids and such usually run
narrow high pressure tires to reduce the rolling resistance.
If you wanted to get the ultimate fuel mileage but didn't care about
ride quality or traction you would run a bare steel tire with close to a
knife edge and NO suspension with ride height as low as possible and
with everything mounted as low as possible to reduce drag.
Take a small flat twin, mount it to a lightweight aluminum frame with
the driver in a prone position and the body faired around the driving
position like a teardrop and three tires with contact patches just large
enough to support the vehicle and driver. You could add in dynamic
steering using body tilt and even have the driver use pedals to assist.
You would get great mileage but forget about
wind/rain/cold/snow/dirt/rough roads/heat or any other comforts.
--
Steve W.
DougC
Feb 7, 2012, 1:11:45 PM2/7/12
to
On 2/2/2012 8:34 PM, RichD wrote:
> Low air pressure in tires retards fuel milege, but why?
>
> The obvious answer is, greater friction. But even though
> the tire is flatter, still it rolls, there's no relative movement
> between the pavement and tire, hence no sliding friction.
>
> So where and how do the losses occur?
>
> --
> Rich
It is not possible to directly compare car tires with bicycle tires,
> Low air pressure in tires retards fuel milege, but why?
>
> The obvious answer is, greater friction. But even though
> the tire is flatter, still it rolls, there's no relative movement
> between the pavement and tire, hence no sliding friction.
>
> So where and how do the losses occur?
>
> --
> Rich
since car tires are generally belted radial construction and bicycle
tires are still only bias-ply (or radial, though none seem to be
currently available).
Belted radial construction is limited to lower pressures but greatly
reduces rolling resistance various ways that can't be done with a
bias-ply or plain radial tire.
Message has been deleted
Message has been deleted
Message has been deleted
thirty-six
Feb 7, 2012, 4:36:44 PM2/7/12
to
On Feb 7, 7:53 pm, Phil W Lee <p...@lee-family.me.uk> wrote:
> gpsman <gps...@driversmail.com> considered Fri, 3 Feb 2012 21:58:52
I'm confident on 24mm tubulars but don't go all out over the roughest
bits. If I thought about it, I'd probably put a little more air in
for the rocky stuff. It's not an ideal situation but it is more than
workable.
> gpsman <gps...@driversmail.com> considered Fri, 3 Feb 2012 21:58:52
> -0800 (PST) the perfect time to write:
>
> >On Feb 4, 12:44 am, Frank Krygowski <frkry...@gmail.com> wrote:
> >> On Feb 3, 6:19 pm, gpsman <gps...@driversmail.com> wrote:
>
> >> > I did not know more tire pressure = more resistance.
>
> >> if the road has any
> >> roughness at all, there will be some tire pressure above which power
> >> requirements will be greater due to greater suspension losses. If that
> >> weren't true, we'd dispense with the air and go back to solid rubber
> >> tires, as hard as possible.
>
> >False premise; fails to consider weight. We needn't delve into the
> >relative "roughness" of road surfaces.
>
> Then you use 23mm road bike tyres off-road then?
>
> >On Feb 4, 12:44 am, Frank Krygowski <frkry...@gmail.com> wrote:
> >> On Feb 3, 6:19 pm, gpsman <gps...@driversmail.com> wrote:
>
> >> > I did not know more tire pressure = more resistance.
>
> >> if the road has any
> >> roughness at all, there will be some tire pressure above which power
> >> requirements will be greater due to greater suspension losses. If that
> >> weren't true, we'd dispense with the air and go back to solid rubber
> >> tires, as hard as possible.
>
> >False premise; fails to consider weight. We needn't delve into the
> >relative "roughness" of road surfaces.
>
I'm confident on 24mm tubulars but don't go all out over the roughest
bits. If I thought about it, I'd probably put a little more air in
for the rocky stuff. It's not an ideal situation but it is more than
workable.
thirty-six
Feb 7, 2012, 4:39:07 PM2/7/12
to
On Feb 7, 7:51 pm, Phil W Lee <p...@lee-family.me.uk> wrote:
> gpsman <gps...@driversmail.com> considered Fri, 3 Feb 2012 15:19:57
> energy bouncing from one bump to the next.
> Most often seen on road bikes with 23mm tyres on coarse chip & seal
> roads.
You need to be specific and say high-pressure covers. Tubulars cope
well with coarse chip[ings at least at appropriate pressure.
>
> >- gpsman
> gpsman <gps...@driversmail.com> considered Fri, 3 Feb 2012 15:19:57
> -0800 (PST) the perfect time to write:
>
>
> >On Feb 3, 4:58 pm, Frank Krygowski <frkry...@gmail.com> wrote:
>
> >> What seems to be different about bikes and cars is that, AFAIK, a
> >> car's gas mileage doesn't decrease if you have tire pressure too high,
> >> at least within reasonable limits. But a bike can take more energy to
> >> move if you have too much pressure.
>
>
> >> What seems to be different about bikes and cars is that, AFAIK, a
> >> car's gas mileage doesn't decrease if you have tire pressure too high,
> >> at least within reasonable limits. But a bike can take more energy to
> >> move if you have too much pressure.
>
> >I did not know more tire pressure = more resistance.
>
> Only above a certain point, when the tyre becomes so hard you waste
>
> energy bouncing from one bump to the next.
> Most often seen on road bikes with 23mm tyres on coarse chip & seal
> roads.
You need to be specific and say high-pressure covers. Tubulars cope
well with coarse chip[ings at least at appropriate pressure.
>
>
>
>
>
>
>
>
>
> >> The difference seems to be
> >> related to lack of mechanical suspension on a bike; the bike tire is
> >> typically the only suspension, and too much pressure makes the bike a
> >> rigid, unsuspended vehicle.
>
> >From here, the difference seems to be your ability to imagine you know
> >what you're talking about.
> > -----
>
>
>
>
>
>
>
>
> >> The difference seems to be
> >> related to lack of mechanical suspension on a bike; the bike tire is
> >> typically the only suspension, and too much pressure makes the bike a
> >> rigid, unsuspended vehicle.
>
> >From here, the difference seems to be your ability to imagine you know
> >what you're talking about.
>
> >- gpsman
Message has been deleted
Kerry Montgomery
Feb 8, 2012, 12:10:33 AM2/8/12
to
"Phil W Lee" <ph...@lee-family.me.uk> wrote in message
news:scv2j7d4icoktqvus...@4ax.com...
> Frank Krygowski <frkr...@gmail.com> considered Fri, 3 Feb 2012
> 13:58:03 -0800 (PST) the perfect time to write:
>
>>On Feb 2, 9:34 pm, RichD <r_delaney2...@yahoo.com> wrote:
>>> Low air pressure in tires retards fuel milege, but why?
>>>
>>> The obvious answer is, greater friction. But even though
>>> the tire is flatter, still it rolls, there's no relative movement
>>> between the pavement and tire, hence no sliding friction.
>>>
>>> So where and how do the losses occur?
>>
>>Friction losses within the tire's material is certainly one way. I
>>On Feb 2, 9:34 pm, RichD <r_delaney2...@yahoo.com> wrote:
>>> Low air pressure in tires retards fuel milege, but why?
>>>
>>> The obvious answer is, greater friction. But even though
>>> the tire is flatter, still it rolls, there's no relative movement
>>> between the pavement and tire, hence no sliding friction.
>>>
>>> So where and how do the losses occur?
>>
>>think if you lowered one of your car's tires to, say, 20 psi and drove
>>on the freeway for a mile, you could easily detect that the tire was
>>hotter, indicating that it's sucking up energy. Admittedly, I don't
>>plan to try that test myself.
>>
>>Think about dribbling a basketball. If the ball's soft, it doesn't
>>rebound nearly as well. Obviously more energy is lost. It's probably
>>going into the rubber.
>>
>>Also, I think there would be more relative movement between the
>>pavement and tire, due to a sort of scrubbing action. Tires that are
>>consistently run with pressure that's too low tend to wear faster,
>>mostly toward the edges.
>>
>>What seems to be different about bikes and cars is that, AFAIK, a
>>car's gas mileage doesn't decrease if you have tire pressure too high,
>>at least within reasonable limits.
>
> Actually, it does, but grip decreases as well, so nobody will admit to
>>What seems to be different about bikes and cars is that, AFAIK, a
>>car's gas mileage doesn't decrease if you have tire pressure too high,
>>at least within reasonable limits.
>
> it, out of a perfectly reasonable fear that the stingy will go around
> with their tyres pumped up so hard they double their stopping
> distances :)
>
>> But a bike can take more energy to
>>move if you have too much pressure. The difference seems to be
>> But a bike can take more energy to
>>related to lack of mechanical suspension on a bike; the bike tire is
>>typically the only suspension, and too much pressure makes the bike a
>>rigid, unsuspended vehicle.
>
> No - it's to do with the difference in contact area.
>>typically the only suspension, and too much pressure makes the bike a
>>rigid, unsuspended vehicle.
>
> If you used a motor vehicle on a road with surface irregularities that
> were proportionate to what exists for a bicycle's contact patch (which
> would be a truly atrocious road surface - something like 5-6" lumps
> with gaps of 8-10" distance between them), you'd see the same results.
>
> That's why vehicles designed for such terrain have huge soft tyres.
>>
>>- Frank Krygowski
>
> Race teams use a tyre thermometer to ensure the tyre pressure is right
> for the load and conditions.
> If you watch an F1 pitstop closely, you'll see the guy with the probe
> stabbing the tread as soon as the car stops.
Phil W Lee,
I don't think that's the case now - the cars are stationary for only 3
seconds or so. And, the cars have tire temperature telemetry (IR sensors)
that monitor tire temperatures in real time.
Kerry
Frank Krygowski
Feb 8, 2012, 12:15:56 AM2/8/12
to
On Feb 7, 12:05 pm, "Noone" <no...@nowhere.com> wrote:
> "Frank Krygowski" <frkry...@gmail.com> wrote in message
More or less. I didn't mean the overall outside diameter of the tire
+wheel (i.e. roughly 27") but the diameter of the tire's cross section
(roughly 1").
But my "something like 15%" is merely working from dim memory of what
the tire literature said. Given that I'm not sure of the exact
percentage, the difference between sidewall height and cross section
diameter isn't very important.
- Frank Krygowski
> "Frank Krygowski" <frkry...@gmail.com> wrote in message
+wheel (i.e. roughly 27") but the diameter of the tire's cross section
(roughly 1").
But my "something like 15%" is merely working from dim memory of what
the tire literature said. Given that I'm not sure of the exact
percentage, the difference between sidewall height and cross section
diameter isn't very important.
- Frank Krygowski
Frank Krygowski
Feb 8, 2012, 12:19:04 AM2/8/12
to
On Feb 7, 2:49 pm, Phil W Lee <p...@lee-family.me.uk> wrote:
> Frank Krygowski <frkry...@gmail.com> considered Fri, 3 Feb 2012
- Frank Krygowski
> Frank Krygowski <frkry...@gmail.com> considered Fri, 3 Feb 2012
> 13:58:03 -0800 (PST) the perfect time to write:
>
>
>
>
> >What seems to be different about bikes and cars is that, AFAIK, a
> >car's gas mileage doesn't decrease if you have tire pressure too high,
> >at least within reasonable limits.
>
> >car's gas mileage doesn't decrease if you have tire pressure too high,
> >at least within reasonable limits.
>
> Actually, it does, but grip decreases as well, so nobody will admit to
> it, out of a perfectly reasonable fear that the stingy will go around
> with their tyres pumped up so hard they double their stopping
> distances :)
You may have misread my "decrease" as "increase."
> it, out of a perfectly reasonable fear that the stingy will go around
> with their tyres pumped up so hard they double their stopping
> distances :)
- Frank Krygowski
James
Feb 8, 2012, 1:44:22 AM2/8/12
to
Maybe the difference gets lost in the noise ;-)
--
JS.
Message has been deleted
Scott Dorsey
Feb 8, 2012, 12:00:14 PM2/8/12
to
Phil W Lee <ph...@lee-family.me.uk> wrote:
>
>To clarify, overpressure in car tyres will get you further on a given
>amount of fuel, but wear out the tyre faster, owing to all the wear
>being on a smaller contact area. This also reduces grip for all
>purposes - acceleration, braking and cornering.
My uncle Ralph claimed that you could never overfill a tire, that you should
just get a pump, and pump air in until you can't get any more in there and
that was the right amount of air.
Surprisingly enough, he was not killed in a car accident.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
>
>To clarify, overpressure in car tyres will get you further on a given
>amount of fuel, but wear out the tyre faster, owing to all the wear
>being on a smaller contact area. This also reduces grip for all
>purposes - acceleration, braking and cornering.
My uncle Ralph claimed that you could never overfill a tire, that you should
just get a pump, and pump air in until you can't get any more in there and
that was the right amount of air.
Surprisingly enough, he was not killed in a car accident.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
(PeteCresswell)
Feb 8, 2012, 12:40:30 PM2/8/12
to
Per Scott Dorsey:
Can somebody explain it for the temporarily humor-impaired?
--
Pete Cresswell
>My uncle Ralph claimed that you could never overfill a tire, that you should
>just get a pump, and pump air in until you can't get any more in there and
>that was the right amount of air.
>
>Surprisingly enough, he was not killed in a car accident.
That one went right over my head.
>just get a pump, and pump air in until you can't get any more in there and
>that was the right amount of air.
>
>Surprisingly enough, he was not killed in a car accident.
Can somebody explain it for the temporarily humor-impaired?
--
Pete Cresswell
DougC
Feb 8, 2012, 3:44:51 PM2/8/12
to
On 2/7/2012 11:02 AM, carl...@comcast.net wrote:
>
> ...
I would not expect the thin/flexible walls of a typical narrow road
bicycle tire to contribute much of any support simply through their own
shape.
> Only in a narrow range of medium pressures does the contact patch
> spread out at an even pressure to match our expectations.
>
I would guess,,, not so.
With any non-belted bicycle tire, the tire inflation doesn't matter much
to the rolling resistance since they suffer from tread squirm at all
pressures. While a higher pressure results in a smaller contact patch,
the tread squirm decreases in size (due to the smaller contact patch)
but also occurs at a higher pressure.
>
> ...
> The reason is that the pressure is not even on the contact patch, due
> to the sidewall acting somewhat like a scissors jack when its curved
> shape distorts.
>
> At low pressures, a halo of high pressure forms around the edges of
> the contact patch.
>
> At high pressures, a halo of low pressure forms around the edges.
>
Is there any imaging of this phenomenon?
> to the sidewall acting somewhat like a scissors jack when its curved
> shape distorts.
>
> At low pressures, a halo of high pressure forms around the edges of
> the contact patch.
>
> At high pressures, a halo of low pressure forms around the edges.
>
I would not expect the thin/flexible walls of a typical narrow road
bicycle tire to contribute much of any support simply through their own
shape.
> Only in a narrow range of medium pressures does the contact patch
> spread out at an even pressure to match our expectations.
>
With any non-belted bicycle tire, the tire inflation doesn't matter much
to the rolling resistance since they suffer from tread squirm at all
pressures. While a higher pressure results in a smaller contact patch,
the tread squirm decreases in size (due to the smaller contact patch)
but also occurs at a higher pressure.
Duane
Feb 8, 2012, 4:13:06 PM2/8/12
to
Kerry Montgomery
Feb 8, 2012, 4:19:26 PM2/8/12
to
"DougC" <dci...@norcom2000.com> wrote in message
news:99BYq.20965$Sh7....@newsfe15.iad...
Are you saying that tread squirm is a much greater contributor to rolling
resistance of non-belted bicycle tires than the tire inflation pressure? For
all values of inflation pressure? For all tread depths? For all road
surfaces? If not, please clarify. If so, then do you contend that a silk
track sew-up on smooth concrete will not have much difference in rolling
resistance if it is inflated to 1 bar or if it is inflated to 8 bar?
Thanks,
Kerry
carl...@comcast.net
Feb 8, 2012, 6:07:13 PM2/8/12
to
On Wed, 08 Feb 2012 14:44:51 -0600, DougC <dci...@norcom2000.com>
wrote:
Dear Doug,
Yes, measurements of the contact patches of bicycle tires confirmed
that they act like car tires, where the non-linear relationship
between pressure and area is well-known. Tire patches were 20~30%
smaller/lower than predicted at high/low pressures. In other words,
the tires stubbornly try to remain at the sweet spot in the middle,
where the sidewall effects are minimized. Tom Schmitz put my
measurements of a single tire to shame with a wide variety of much
more carefully-done tests--and the curve of his average measurements
overlaid my single-tire tests:
http://groups.google.com/group/rec.bicycles.tech/msg/ddd6c10253d9f70c
The scissors-jack effect doesn't depend on the thickness of the walls
of the tire--a good deal of force is needed to distort the curve of
the sidewalls, which leads to the halo of high pressure at low
pressures.
As for the halo of low-pressure at high pressures, that's easier to
understand. Assume a 150 psi inflation. Pressure at the center of the
tire patch is 150 psi. Near the edges, the tire starts to curve away
from the ground, until the 150 psi tire's pressure on the ground drops
to zero.
In the end, fairly simple physics explains the easily reproducible
results. Just pump a bicycle tire to 100 psi, ink it, lower it with a
100 lb weight onto paper (or glass as Tom did), measure the two
dimensions of the ellipse, and then repeat at 10 psi increments for a
range from 40 to 150 psi. As I mentioned, the effect is well-known in
automobile tire engineering.
Cheers,
Carl Fogel
wrote:
Yes, measurements of the contact patches of bicycle tires confirmed
that they act like car tires, where the non-linear relationship
between pressure and area is well-known. Tire patches were 20~30%
smaller/lower than predicted at high/low pressures. In other words,
the tires stubbornly try to remain at the sweet spot in the middle,
where the sidewall effects are minimized. Tom Schmitz put my
measurements of a single tire to shame with a wide variety of much
more carefully-done tests--and the curve of his average measurements
overlaid my single-tire tests:
http://groups.google.com/group/rec.bicycles.tech/msg/ddd6c10253d9f70c
The scissors-jack effect doesn't depend on the thickness of the walls
of the tire--a good deal of force is needed to distort the curve of
the sidewalls, which leads to the halo of high pressure at low
pressures.
As for the halo of low-pressure at high pressures, that's easier to
understand. Assume a 150 psi inflation. Pressure at the center of the
tire patch is 150 psi. Near the edges, the tire starts to curve away
from the ground, until the 150 psi tire's pressure on the ground drops
to zero.
In the end, fairly simple physics explains the easily reproducible
results. Just pump a bicycle tire to 100 psi, ink it, lower it with a
100 lb weight onto paper (or glass as Tom did), measure the two
dimensions of the ellipse, and then repeat at 10 psi increments for a
range from 40 to 150 psi. As I mentioned, the effect is well-known in
automobile tire engineering.
Cheers,
Carl Fogel
Message has been deleted
Vic Smith
Feb 8, 2012, 6:45:45 PM2/8/12
to
On Wed, 08 Feb 2012 12:40:30 -0500, "(PeteCresswell)" <x...@y.Invalid>
wrote:
Got nothing to do with humor unless you have the uncle.
It's about uncles with bad ideas, which they thought was common sense.
If somebody would argue with Scott's uncle about that air pressure, he
might say something like,
"You don't know much about equalization, do you? Common sense."
I had one like that.
I was his favorite nephew, because I fished with him, and usually
brought the beer.
And I liked his jokes. Man, he could tell jokes.
First time we went together in my car, he was totally shocked when he
saw me fasten my seat belt.
Seat belts were pretty new then.
Started yelling at me,
"What the hell you doing that for??!!"
I told him it was safer.
He looked at me like I as stupidest man alive, and said,
"Safe?!! What if you go in the river and can't get loose?!"
Anyway, you have to be there.
--Vic
wrote:
It's about uncles with bad ideas, which they thought was common sense.
If somebody would argue with Scott's uncle about that air pressure, he
might say something like,
"You don't know much about equalization, do you? Common sense."
I had one like that.
I was his favorite nephew, because I fished with him, and usually
brought the beer.
And I liked his jokes. Man, he could tell jokes.
First time we went together in my car, he was totally shocked when he
saw me fasten my seat belt.
Seat belts were pretty new then.
Started yelling at me,
"What the hell you doing that for??!!"
I told him it was safer.
He looked at me like I as stupidest man alive, and said,
"Safe?!! What if you go in the river and can't get loose?!"
Anyway, you have to be there.
--Vic
James
Feb 8, 2012, 6:51:50 PM2/8/12
to
I imagine that with the aid of some integral calculus, the contact
pressure variation and patch size can be explained. It would be
interesting to see the results. One day maybe I'll try tackling such a
problem, unless someone beats me to it.
--
JS.
DirtRoadie
Feb 8, 2012, 7:03:34 PM2/8/12
to
On Feb 8, 4:45 pm, Vic Smith <thismailautodele...@comcast.net> wrote:
> First time we went together in my car, he was totally shocked when he
> saw me fasten my seat belt.
> Seat belts were pretty new then.
> Started yelling at me,
> "What the hell you doing that for??!!"
> I told him it was safer.
> He looked at me like I as stupidest man alive, and said,
> "Safe?!! What if you go in the river and can't get loose?!"
>
> Anyway, you have to be there.
Being here is often enough.
> First time we went together in my car, he was totally shocked when he
> saw me fasten my seat belt.
> Seat belts were pretty new then.
> Started yelling at me,
> "What the hell you doing that for??!!"
> I told him it was safer.
> He looked at me like I as stupidest man alive, and said,
> "Safe?!! What if you go in the river and can't get loose?!"
>
> Anyway, you have to be there.
http://groups.google.com/group/rec.bicycles.tech/msg/2bf6f355644c4c08
DR
Scott Dorsey
Feb 8, 2012, 8:01:06 PM2/8/12
to
Vic Smith <thismaila...@comcast.net> wrote:
>On Wed, 08 Feb 2012 12:40:30 -0500, "(PeteCresswell)" <x...@y.Invalid>
>wrote:
>
>>Per Scott Dorsey:
>>>My uncle Ralph claimed that you could never overfill a tire, that you should
>>>just get a pump, and pump air in until you can't get any more in there and
>>>that was the right amount of air.
>>>
>>>Surprisingly enough, he was not killed in a car accident.
>>
>>That one went right over my head.
>>
>>Can somebody explain it for the temporarily humor-impaired?
>
>Got nothing to do with humor unless you have the uncle.
>It's about uncles with bad ideas, which they thought was common sense.
Precisely. And, it's possible that all he ever used was a foot pump so
>On Wed, 08 Feb 2012 12:40:30 -0500, "(PeteCresswell)" <x...@y.Invalid>
>wrote:
>
>>Per Scott Dorsey:
>>>My uncle Ralph claimed that you could never overfill a tire, that you should
>>>just get a pump, and pump air in until you can't get any more in there and
>>>that was the right amount of air.
>>>
>>>Surprisingly enough, he was not killed in a car accident.
>>
>>That one went right over my head.
>>
>>Can somebody explain it for the temporarily humor-impaired?
>
>Got nothing to do with humor unless you have the uncle.
>It's about uncles with bad ideas, which they thought was common sense.
there was some limit to the pressure he could get in the tire. But he
harbored a pretty serious delusion and it is a miracle he wasn't killed
by it.
>If somebody would argue with Scott's uncle about that air pressure, he
>might say something like,
>"You don't know much about equalization, do you? Common sense."
Alan Baker
Feb 19, 2012, 12:46:33 AM2/19/12
to
In article
<5bdfcb4e-a66f-4612...@y5g2000pbk.googlegroups.com>,
> Rich
Flexing the rubber.
More flex, more energy lost.
--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling four feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect if you
sit in the bottom of that cupboard."
<5bdfcb4e-a66f-4612...@y5g2000pbk.googlegroups.com>,
RichD <r_dela...@yahoo.com> wrote:
> Low air pressure in tires retards fuel milege, but why?
>
> The obvious answer is, greater friction. But even though
> the tire is flatter, still it rolls, there's no relative movement
> between the pavement and tire, hence no sliding friction.
>
> So where and how do the losses occur?
>
> --
> Low air pressure in tires retards fuel milege, but why?
>
> The obvious answer is, greater friction. But even though
> the tire is flatter, still it rolls, there's no relative movement
> between the pavement and tire, hence no sliding friction.
>
> So where and how do the losses occur?
>
> Rich
Flexing the rubber.
More flex, more energy lost.
--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling four feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect if you
sit in the bottom of that cupboard."
Kevin Bottorff
Feb 19, 2012, 6:44:35 PM2/19/12
to
Alan Baker <alang...@telus.net> wrote in news:alangbaker-
857062.214...@news.shawcable.net:
> In article
> <5bdfcb4e-a66f-4612...@y5g2000pbk.googlegroups.com>,
> RichD <r_dela...@yahoo.com> wrote:
>
>> Low air pressure in tires retards fuel milege, but why?
>>
>> The obvious answer is, greater friction. But even though
>> the tire is flatter, still it rolls, there's no relative movement
>> between the pavement and tire, hence no sliding friction.
>>
>> So where and how do the losses occur?
>>
>> --
>> Rich
>
> Flexing the rubber.
>
> More flex, more energy lost.
>
no one has stated the largest one yet!!!! the lower the pressure the
smaller the actuall dia of the rotating tire, lowering the overall ratio,
less distance traveled per rev. less milage. KB
857062.214...@news.shawcable.net:
> In article
> <5bdfcb4e-a66f-4612...@y5g2000pbk.googlegroups.com>,
> RichD <r_dela...@yahoo.com> wrote:
>
>> Low air pressure in tires retards fuel milege, but why?
>>
>> The obvious answer is, greater friction. But even though
>> the tire is flatter, still it rolls, there's no relative movement
>> between the pavement and tire, hence no sliding friction.
>>
>> So where and how do the losses occur?
>>
>> --
>> Rich
>
> Flexing the rubber.
>
> More flex, more energy lost.
>
smaller the actuall dia of the rotating tire, lowering the overall ratio,
less distance traveled per rev. less milage. KB
jim beam
Feb 19, 2012, 11:51:32 PM2/19/12
to
gearing does - some cars use /more/ gas in overdrive than they do the
next gear down.
--
nomina rutrum rutrum
kolldata
Feb 19, 2012, 11:57:30 PM2/19/12
to
On Feb 19, 9:51 pm, jim beam <m...@privacy.net> wrote:
> On 02/19/2012 03:44 PM, Kevin Bottorff wrote:
>
>
>
>
>
> > Alan Baker<alangba...@telus.net> wrote in news:alangbaker-
> On 02/19/2012 03:44 PM, Kevin Bottorff wrote:
>
>
>
>
>
> > 857062.21463218022...@news.shawcable.net:
>
> >> In article
> >> <5bdfcb4e-a66f-4612-8d25-8dfff8a09...@y5g2000pbk.googlegroups.com>,
> >> RichD<r_delaney2...@yahoo.com> wrote:
>
> >>> Low air pressure in tires retards fuel milege, but why?
>
> >>> The obvious answer is, greater friction. But even though
> >>> the tire is flatter, still it rolls, there's no relative movement
> >>> between the pavement and tire, hence no sliding friction.
>
> >>> So where and how do the losses occur?
>
> >>> --
> >>> Rich
>
> >> Flexing the rubber.
>
> >> More flex, more energy lost.
>
> > no one has stated the largest one yet!!!! the lower the pressure the
> > smaller the actuall dia of the rotating tire, lowering the overall ratio,
> > less distance traveled per rev. less milage. KB
>
> bull. tire size has no more to do with mileage than transmission
> gearing does - some cars use /more/ gas in overdrive than they do the
> next gear down.
>
> --
> nomina rutrum rutrum- Hide quoted text -
> >>> Low air pressure in tires retards fuel milege, but why?
>
> >>> The obvious answer is, greater friction. But even though
> >>> the tire is flatter, still it rolls, there's no relative movement
> >>> between the pavement and tire, hence no sliding friction.
>
> >>> So where and how do the losses occur?
>
> >>> --
> >>> Rich
>
> >> Flexing the rubber.
>
> >> More flex, more energy lost.
>
> > no one has stated the largest one yet!!!! the lower the pressure the
> > smaller the actuall dia of the rotating tire, lowering the overall ratio,
> > less distance traveled per rev. less milage. KB
>
> bull. tire size has no more to do with mileage than transmission
> gearing does - some cars use /more/ gas in overdrive than they do the
> next gear down.
>
> --
>
> - Show quoted text -
Jesus ! they let you out ?
escopia cidularus
jim beam
Feb 20, 2012, 12:25:59 AM2/20/12
to
i'm no different now i'm clearly losing my faculties by forgetting to
delete that group from my response.
anyway, glad you seem to be surviving.
--
nomina rutrum rutrum
thirty-six
Feb 20, 2012, 1:17:31 AM2/20/12
to
On Feb 20, 4:51 am, jim beam <m...@privacy.net> wrote:
> On 02/19/2012 03:44 PM, Kevin Bottorff wrote:
>
>
>
>
>
>
>
>
>
> On 02/19/2012 03:44 PM, Kevin Bottorff wrote:
>
>
>
>
>
>
>
>
>
> > Alan Baker<alangba...@telus.net> wrote in news:alangbaker-
> > 857062.21463218022...@news.shawcable.net:
>
> >> In article
> >> <5bdfcb4e-a66f-4612-8d25-8dfff8a09...@y5g2000pbk.googlegroups.com>,
> >> RichD<r_delaney2...@yahoo.com> wrote:
> > 857062.21463218022...@news.shawcable.net:
>
> >> In article
> >> <5bdfcb4e-a66f-4612-8d25-8dfff8a09...@y5g2000pbk.googlegroups.com>,
>
> >>> Low air pressure in tires retards fuel milege, but why?
>
> >>> The obvious answer is, greater friction. But even though
> >>> the tire is flatter, still it rolls, there's no relative movement
> >>> between the pavement and tire, hence no sliding friction.
>
> >>> So where and how do the losses occur?
>
> >>> --
> >>> Rich
>
> >> Flexing the rubber.
>
> >> More flex, more energy lost.
>
> > no one has stated the largest one yet!!!! the lower the pressure the
> > smaller the actuall dia of the rotating tire, lowering the overall ratio,
> > less distance traveled per rev. less milage. KB
>
> bull. tire size has no more to do with mileage than transmission
> gearing does - some cars use /more/ gas in overdrive than they do the
> next gear down.
>
> --
> nomina rutrum rutrum
cor,isit that time agaim?
> >>> Low air pressure in tires retards fuel milege, but why?
>
> >>> The obvious answer is, greater friction. But even though
> >>> the tire is flatter, still it rolls, there's no relative movement
> >>> between the pavement and tire, hence no sliding friction.
>
> >>> So where and how do the losses occur?
>
> >>> --
> >>> Rich
>
> >> Flexing the rubber.
>
> >> More flex, more energy lost.
>
> > no one has stated the largest one yet!!!! the lower the pressure the
> > smaller the actuall dia of the rotating tire, lowering the overall ratio,
> > less distance traveled per rev. less milage. KB
>
> bull. tire size has no more to do with mileage than transmission
> gearing does - some cars use /more/ gas in overdrive than they do the
> next gear down.
>
> --
> nomina rutrum rutrum
thirty-six
Feb 20, 2012, 1:26:55 AM2/20/12
to
On Feb 20, 4:51 am, jim beam <m...@privacy.net> wrote:
> On 02/19/2012 03:44 PM, Kevin Bottorff wrote:
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> > Alan Baker<alangba...@telus.net> wrote in news:alangbaker-
> > 857062.21463218022...@news.shawcable.net:
>
> >> In article
> >> <5bdfcb4e-a66f-4612-8d25-8dfff8a09...@y5g2000pbk.googlegroups.com>,
> >> RichD<r_delaney2...@yahoo.com> wrote:
> > 857062.21463218022...@news.shawcable.net:
>
> >> In article
> >> <5bdfcb4e-a66f-4612-8d25-8dfff8a09...@y5g2000pbk.googlegroups.com>,
>
> >>> Low air pressure in tires retards fuel milege, but why?
>
> >>> The obvious answer is, greater friction. But even though
> >>> the tire is flatter, still it rolls, there's no relative movement
> >>> between the pavement and tire, hence no sliding friction.
>
> >>> So where and how do the losses occur?
>
> >>> --
> >>> Rich
>
> >> Flexing the rubber.
>
> >> More flex, more energy lost.
>
> > no one has stated the largest one yet!!!! the lower the pressure the
> > smaller the actuall dia of the rotating tire, lowering the overall ratio,
> > less distance traveled per rev. less milage. KB
>
> bull. tire size has no more to do with mileage than transmission
> gearing does - some cars use /more/ gas in overdrive than they do the
> next gear down.
You might like to use a synthetic gearbox oil and engine oil to
> >>> Low air pressure in tires retards fuel milege, but why?
>
> >>> The obvious answer is, greater friction. But even though
> >>> the tire is flatter, still it rolls, there's no relative movement
> >>> between the pavement and tire, hence no sliding friction.
>
> >>> So where and how do the losses occur?
>
> >>> --
> >>> Rich
>
> >> Flexing the rubber.
>
> >> More flex, more energy lost.
>
> > no one has stated the largest one yet!!!! the lower the pressure the
> > smaller the actuall dia of the rotating tire, lowering the overall ratio,
> > less distance traveled per rev. less milage. KB
>
> bull. tire size has no more to do with mileage than transmission
> gearing does - some cars use /more/ gas in overdrive than they do the
> next gear down.
correct that problem.
>
BTW I couldn't be arsed answering such an obviously erroneous
statement and thought it'd be better left to some dick to make a
pointless argument Youv'e saved the bother of embarresment of the
innocent by jumping in wellies first wearing a blancmange hat.
Kevin Bottorff
Feb 20, 2012, 4:35:07 PM2/20/12
to
jim beam <m...@privacy.net> wrote in news:jhsjgj$p8v$1...@speranza.aioe.org:
yea the select few that are not enginered correctly, but for most it is
entirely correct, KB
entirely correct, KB
Nate Nagel
Feb 20, 2012, 5:29:50 PM2/20/12
to
correctly."
nate
--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel
Dan O
Feb 20, 2012, 10:38:32 PM2/20/12
to
On Feb 20, 2:29 pm, Nate Nagel <njna...@roosters.net> wrote:
> On 02/20/2012 04:35 PM, Kevin Bottorff wrote:
>
>
>
> > jim beam<m...@privacy.net> wrote innews:jhsjgj$p8v$1...@speranza.aioe.org:
> On 02/20/2012 04:35 PM, Kevin Bottorff wrote:
>
>
>
>
> >> On 02/19/2012 03:44 PM, Kevin Bottorff wrote:
> >> On 02/19/2012 03:44 PM, Kevin Bottorff wrote:
> >>> Alan Baker<alangba...@telus.net> wrote in news:alangbaker-
> >>> 857062.21463218022...@news.shawcable.net:
>
> >>>> In article
> >>>> <5bdfcb4e-a66f-4612-8d25-8dfff8a09...@y5g2000pbk.googlegroups.com>,
> >>> 857062.21463218022...@news.shawcable.net:
>
> >>>> In article
> >>>> <5bdfcb4e-a66f-4612-8d25-8dfff8a09...@y5g2000pbk.googlegroups.com>,
> >>>> RichD<r_delaney2...@yahoo.com> wrote:
>
> >>>>> Low air pressure in tires retards fuel milege, but why?
>
> >>>>> The obvious answer is, greater friction. But even though
> >>>>> the tire is flatter, still it rolls, there's no relative movement
> >>>>> between the pavement and tire, hence no sliding friction.
>
> >>>>> So where and how do the losses occur?
>
> >>>>> --
> >>>>> Rich
>
> >>>> Flexing the rubber.
>
> >>>> More flex, more energy lost.
>
> >>> no one has stated the largest one yet!!!! the lower the pressure the
> >>> smaller the actuall dia of the rotating tire, lowering the overall
> >>> ratio, less distance traveled per rev. less milage. KB
>
> >> bull. tire size has no more to do with mileage than transmission
> >> gearing does - some cars use /more/ gas in overdrive than they do the
> >> next gear down.
>
> > yea the select few that are not enginered correctly, but for most it is
> > entirely correct, KB
>
> Depends on the speed and grade, not whether the car is "engineered
> correctly."
>
The OP asks why lower tire pressure takes more energy, and now you're
>
> >>>>> Low air pressure in tires retards fuel milege, but why?
>
> >>>>> The obvious answer is, greater friction. But even though
> >>>>> the tire is flatter, still it rolls, there's no relative movement
> >>>>> between the pavement and tire, hence no sliding friction.
>
> >>>>> So where and how do the losses occur?
>
> >>>>> --
> >>>>> Rich
>
> >>>> Flexing the rubber.
>
> >>>> More flex, more energy lost.
>
> >>> no one has stated the largest one yet!!!! the lower the pressure the
> >>> smaller the actuall dia of the rotating tire, lowering the overall
> >>> ratio, less distance traveled per rev. less milage. KB
>
> >> bull. tire size has no more to do with mileage than transmission
> >> gearing does - some cars use /more/ gas in overdrive than they do the
> >> next gear down.
>
> > yea the select few that are not enginered correctly, but for most it is
> > entirely correct, KB
>
> Depends on the speed and grade, not whether the car is "engineered
> correctly."
>
arguing about hills?
N8N
Feb 21, 2012, 4:59:54 PM2/21/12
to
entirely possible to have a car that gets better mileage in OD on the
flat and better mileage in 3rd or 4th climbing a hill. just as you
may burn more calories in the wrong gear on a bike. Different gears
exist for different purposes... otherwise you'd just leave it in the
highest gear all the time.
The fact that OD (or the highest gear) isn't ideal for all situations
is not a sign of poor engineering.
nate
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