OT? Weigh your car by checking tire pressure?

ChairmanOfTheBored wrote:
.... snip ...

What DUMB BASTARD that doesn't know a fucking thing about Usenet
made this stupid, cross-posted SHIT?
Click to expand...
PLONK

--
Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home.att.net>


--
Posted via a free Usenet account from http://www.teranews.com
 
On Sep 22, 7:32?pm, Rich Grise <r...@example.net> wrote:
Saturday morning TV is mostly cartoons, yes, but there's one show that's
not a cartoon, but it's still fun:http://www.beakmansworldtv.com/

It's like Stealth Educational TV - like Mr. Wizard for the 21st century
kid. And they do Real Science.

But today, they said that you can weigh your car by using your tire
pressure. What you do is measure the footprint of each tire, take its
pressure, and then the footprint of the tire times the PSI equals
the number of pounds that the tire is supporting, and their sum is the
weight of the car. (except for the tires themselves, I presume).

But they did the experiment - they measured the footprints of the four
tires on Some very well-preserved Nash Rambler, and their PSI, and did
the arithmetic, and came up with a number that was within 10% of the car's
"official" weight.

Well, I'm a little uncomfortable with that. What about the pressure that's
in a tire when it's not on the car? Where does that pressure go? Is that
that 10% fudge factor that they admitted to in the show?

How much does the pressure change when you take a standalone tire, mount
it on the car, and let the car down on it?

Or do they get around that by saying, "Well, you can ignore that, because
the tire's not supporting any weight". Or is it entirely ( or mostly) due
to the flattening of the bottom of the tire? Does the "bias pressure" (a
term I just made up now, for the pressure that's there when it's not on
the car) get lost below the noise floor?

Thanks,
Rich
Click to expand...
Take the car and launch it into orbit.
Then, measure the tire pressure and determine the weight.
 
In article <fd4rnn$ccu$1@registered.motzarella.org>,
E Z Peaces <cash@invalid.invalid> wrote:
I've read that tires of larger diameter have less rolling resistance,
but for some reason tires of smaller diameter hold better on snow. The
contact patches are the same area.
Click to expand...
I think the important factor is width, not diameter.

The contact patches are the same size, but a different shape. After
the first part of the contact patch has displaced the snow, there's
more contact patch left in a narrow tire to contact the pavement. The
amount of snow which needs to be displaced is proportional to the
width of the contact patch, not the area.

I don't know why a tire of larger width would have less rolling
resistance, unless it's just that tires of larger width usually have a
smaller sidewall (proportionally) when used on the same car.
--
There's no such thing as a free lunch, but certain accounting practices can
result in a fully-depreciated one.
 
On Sun, 23 Sep 2007 13:35:15 -0700, Gunner Asch
<gunner@NOSPAM.earthlink.net> wrote:

On Sun, 23 Sep 2007 12:10:07 -0700, ChairmanOfTheBored
RUBored@crackasmile.org> wrote:

What DUMB BASTARD that doesn't know a fucking thing about Usenet made
this stupid, cross-posted SHIT?


Evidently it was you.

Gunner
Click to expand...

Responses don't count, dipshit. I have to ensure that my post gets read
by the twit that posted across several groups, many of which he may not
even visit or pull headers from. Get a clue.
 
On Sun, 23 Sep 2007 19:10:43 -0400, CBFalconer <cbfalconer@yahoo.com>
wrote:

ChairmanOfTheBored wrote:

... snip ...

What DUMB BASTARD that doesn't know a fucking thing about Usenet
made this stupid, cross-posted SHIT?

PLONK
Click to expand...

The only thing more retarded than a cross-posting original post author,
is some retarded twit that actually thinks that his filter file edit
session announcements mean a fucking thing to anyone.

You are one such retard.
 
On Sun, 23 Sep 2007 20:55:59 -0500, russotto@grace.speakeasy.net (Matthew
T. Russotto) wrote:

I don't know why a tire of larger width would have less rolling
resistance, unless it's just that tires of larger width usually have a
smaller sidewall (proportionally) when used on the same car.
Click to expand...

As rolling resistance would be a function of the weight they bear, one
would think that the larger distributed weight area (contact patch) would
result in a lower rolling resistance, as there would be less overall
rubber sidewall distortion.

However, they may have a lower fill pressure as well, which might be a
reason for a claim of higher rolling resistance.
 
On Sep 24, 10:16 am, mpm <mpmill...@aol.com> wrote:
On Sep 22, 7:32?pm, Rich Grise <r...@example.net> wrote:



Saturday morning TV is mostly cartoons, yes, but there's one show that's
not a cartoon, but it's still fun:http://www.beakmansworldtv.com/

It's like Stealth Educational TV - like Mr. Wizard for the 21st century
kid. And they do Real Science.

But today, they said that you can weigh your car by using your tire
pressure. What you do is measure the footprint of each tire, take its
pressure, and then the footprint of the tire times the PSI equals
the number of pounds that the tire is supporting, and their sum is the
weight of the car. (except for the tires themselves, I presume).

But they did the experiment - they measured the footprints of the four
tires on Some very well-preserved Nash Rambler, and their PSI, and did
the arithmetic, and came up with a number that was within 10% of the car's
"official" weight.

Well, I'm a little uncomfortable with that. What about the pressure that's
in a tire when it's not on the car? Where does that pressure go? Is that
that 10% fudge factor that they admitted to in the show?

How much does the pressure change when you take a standalone tire, mount
it on the car, and let the car down on it?

Or do they get around that by saying, "Well, you can ignore that, because
the tire's not supporting any weight". Or is it entirely ( or mostly) due
to the flattening of the bottom of the tire? Does the "bias pressure" (a
term I just made up now, for the pressure that's there when it's not on
the car) get lost below the noise floor?

Thanks,
Rich

Take the car and launch it into orbit.
Click to expand...
They tried to do that on Top Gear:
http://www.youtube.com/watch?v=TN3JjUUdjWU

Nice try!

Dave.
 
In article <ni9ef3p3lnk1pshgicbobrei90dmhqsu7i@4ax.com>,
ChairmanOfTheBored <RUBored@crackasmile.org> wrote:
On Sun, 23 Sep 2007 20:55:59 -0500, russotto@grace.speakeasy.net (Matthew
T. Russotto) wrote:

I don't know why a tire of larger width would have less rolling
resistance, unless it's just that tires of larger width usually have a
smaller sidewall (proportionally) when used on the same car.


As rolling resistance would be a function of the weight they bear, one
would think that the larger distributed weight area (contact patch) would
result in a lower rolling resistance, as there would be less overall
rubber sidewall distortion.
Click to expand...
If the tire pressures are the same, the contact patch is the same
(approximately), regardless of the tire width.

However, they may have a lower fill pressure as well, which might be a
reason for a claim of higher rolling resistance.
Click to expand...
Typically lower pressures result in higher rolling resistance, due to
increased sidewall flex.
--
There's no such thing as a free lunch, but certain accounting practices can
result in a fully-depreciated one.
 
On Sun, 23 Sep 2007 19:42:54 -0700, ChairmanOfTheBored
<RUBored@crackasmile.org> wrote:

On Sun, 23 Sep 2007 13:35:15 -0700, Gunner Asch
gunner@NOSPAM.earthlink.net> wrote:

On Sun, 23 Sep 2007 12:10:07 -0700, ChairmanOfTheBored
RUBored@crackasmile.org> wrote:

What DUMB BASTARD that doesn't know a fucking thing about Usenet made
this stupid, cross-posted SHIT?


Evidently it was you.

Gunner


Responses don't count, dipshit. I have to ensure that my post gets read
by the twit that posted across several groups, many of which he may not
even visit or pull headers from. Get a clue.
Click to expand...

so you are admitting to being the DUMB BASTARD that doesnt know a
fucking thing about Usenet who made that stupid cross-posted SHIT.

Thank you for playing

Gunner
 
In article <ni9ef3p3lnk1pshgicbobrei90dmhqsu7i@4ax.com>,
ChairmanOfTheBored wrote:
On Sun, 23 Sep 2007 20:55:59 -0500, russotto@grace.speakeasy.net (Matthew
T. Russotto) wrote:

I don't know why a tire of larger width would have less rolling
resistance, unless it's just that tires of larger width usually have a
smaller sidewall (proportionally) when used on the same car.


As rolling resistance would be a function of the weight they bear, one
would think that the larger distributed weight area (contact patch) would
result in a lower rolling resistance, as there would be less overall
rubber sidewall distortion.

However, they may have a lower fill pressure as well, which might be a
reason for a claim of higher rolling resistance.
Click to expand...
Increasing contact patch length, whether by increasing weight or
decreasing pressure or decreasing tire width, increases sidewall
distortion.

If tire width is increased but pressure and weight are unchanged, the
contact patch length will decrease. I think that would decrease rolling
resistance.

One factor that appears significant is ratio of radii from axle center
to tire surface, at center of contact patch and at forward/rearward
extremes of the contact patch. The closer this ratio is to 1, the less
rolling resistance will be. One reason I see: Less rubbing of tread
against the road surface upon meeting and leaving the road surface. Also
less deformation counts at least a little, even other than by actual
scraping/rubbing of tread on road surface. It appears to me that 1 minus
this radius ratio strongly influences the rolling resistance coefficent.

And tread duration goes largely as:

* Directly proportionately with contact patch width
* Directly proportionately with depth of rubber to wear away
* Inversely proportionately with pressure
* Inversely proportional to either the above {1 minus radius ratio}, or to
actual rolling resistance coefficient (ratio of rolling resistance to
weight supported by the tire including its own)

As pressure increases, tire life tends to increase as long as product of
rolling resistance coefficient (or the above radius ratio) and pressure
decreases more than contact patch width decreases.

In general, tires for vehicles having 4 or more wheels have contact
patch width varying only slightly inversely with pressure, unless the
contact patch width is narrowed by a large pressure uptick, and then maybe
only after the tire has been "broken in" at the lower pressure. That
problem tends to require either overinflation or proper pressure after
experiencing significant wear while underinflated.

One more thing: Assuming tire design that has contact patch width not
varying much with pressure (or ratio of pressure to weight loading), the
above radius ratio is approximating the cosine of the angle between
straight down and from axle center to either forward or rearward end of
the contact patch.
This (1-minus-radius_ratio) in such case tends to be close to inversely
proportional to square of tire pressure (above atmospheric pressure).
That appears to me to indicate that things tend to get better with such
tires as pressure gets higher, as long as the pressure is not exsceeding
the pressure capability of the tire.

One more thing: Tire pressure is supposed to be measured "cold" - when
the tires are not heated up by using them. If the "cold" pressure does
not exceed the maximum rating for the tire, then the "warmed up pressure"
is supposed to be unable to be "excessive" unless the weigt loading
exceeds the tire rating for that, vehicle speed is excessive, or the
ambient temperature takes a jump big enough to be a considerable factor.

If you have excessive weight loading on your tires, then they are unsafe
at any pressure - their deformation varies directly with ratio of weight
loading to pressure, and any fatigue effects of that get worse when the
deformation is greater or the when "same deformation" occurs at higher
pressure - excessive weight loading is bad no matter what you do.
However, in my experience of overloading bicycle tires (by being
adventurous as a bicycle messenger by carrying heavier packages or
clusters thereof), I have found "least-worst" (still "living dangerously")
results from having pressure measured-cold at or a little above the
pressure marking on the sidewall of the tire - I don't see tires having
tolerance of excessive weight load improved by lower pressure; lower
pressure with excessive weight increases bigtime flexing of the sidewall,
and fatigue in the sidewall towards the bead.

- Don Klipstein (don@misty.com)
 
Wasn't it rthearle@hotmail.com who wrote:
On 23 Sep, 00:47, "dcas...@krl.org" <dcas...@krl.org> wrote:

It took me a while before I decided that they are right. When the
tire is not on the ground you multiply the pressure ( Say 30 psi ) by
the footprint ( 0 ) and get zero. The big problem is measuring the
footprint and the stiffness of the tire sidewalls and tread.

I'm tempted to come round and let your tyres down, and watch you try
to catch your now weightless car as it drifts away across the sky...
Click to expand...
Like this? http://tinyurl.com/398wes

--
Mike Williams
Gentleman of Leisure
 
Brian Whatcott betwys1@sbcglobal.net posted to sci.electronics.design:

On Sun, 23 Sep 2007 00:57:26 -0400, E Z Peaces
cash@invalid.invalid> wrote:

... if you measure the tire radius in a horizontal plane, then
measure the distance from the center of the wheel to the ground, you
will know
how much the tire is flexing in mm. Then if you unscrew the valve
core from your spare, you can stand the wheel up and see how much
weight it
takes to push the center of the wheel down to that height. With a
radial, I wonder if the weight of the rim would flex the tire that
much.

It seems to me that except those few pounds, it's air pressure that
holds up an inflated tire. In ordinary circumstances I wouldn't
know
how to measure the footprint accurately. The car would have to be
on a very smooth, flat surface and I would need a thin "feeler
gage."

Here's a question on an engineering group that has an
engineering answer!

There is a pressure sensitive material available (for gaskets etc.)
that color codes the pressure that it experiences.
That would be one analytical approach.

Brian W
Click to expand...
If you use structural strength glass (or other structural transparent
material) with side (edge) lighting the contact area (non-moving)
could be directly observed. Perhaps with a "window" smoothly
embedded in pavement and careful photograph timing the contact patch
could be measured in a variety of circumstances.
 
mpm wrote:
) Take the car and launch it into orbit.
) Then, measure the tire pressure and determine the weight.

Easy:

The contact patch with the ground is zero. Multiply this by
the tire pressure and you get a weight of, you guessed it, zero.


(Determining the mass, however, is an entirely different matter.)
:)


SaSW, Willem
--
Disclaimer: I am in no way responsible for any of the statements
made in the above text. For all I know I might be
drugged or something..
No I'm not paranoid. You all think I'm paranoid, don't you !
#EOT
 
Gunner Asch wrote:
On Sun, 23 Sep 2007 12:10:07 -0700, ChairmanOfTheBored
RUBored@crackasmile.org> wrote:

What DUMB BASTARD that doesn't know a fucking thing about Usenet made
this stupid, cross-posted SHIT?

Evidently it was you.

Gunner
Click to expand...

His real name is 'dimbulb', and he morphs more often than he bathes.
Thats why all his posts stink. ;-)

Don't waste your tinme on him, he's as big a loser as Hawkie, and
Sloman.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
On Sun, 23 Sep 2007 22:24:51 -0500, russotto@grace.speakeasy.net (Matthew
T. Russotto) wrote:

In article <ni9ef3p3lnk1pshgicbobrei90dmhqsu7i@4ax.com>,
ChairmanOfTheBored <RUBored@crackasmile.org> wrote:
On Sun, 23 Sep 2007 20:55:59 -0500, russotto@grace.speakeasy.net (Matthew
T. Russotto) wrote:

I don't know why a tire of larger width would have less rolling
resistance, unless it's just that tires of larger width usually have a
smaller sidewall (proportionally) when used on the same car.


As rolling resistance would be a function of the weight they bear, one
would think that the larger distributed weight area (contact patch) would
result in a lower rolling resistance, as there would be less overall
rubber sidewall distortion.

If the tire pressures are the same, the contact patch is the same
(approximately), regardless of the tire width.

However, they may have a lower fill pressure as well, which might be a
reason for a claim of higher rolling resistance.

Typically lower pressures result in higher rolling resistance, due to
increased sidewall flex.
Click to expand...

Absolutely untrue. There are far too many differences (variables) in
tire construction, such as sidewall strength and the cross sectional
thickness of the tire face, and I am not talking about the tread.

If we were talking about a bunch of balloons which all had the same
wall thicknesses, I would agree, but here... no way.

Look at a dragster tire if you want a comparison. They have very weak
sidewalls. It shows up as soon as they accelerate off the line in
expanded tire diameter.
 
On Mon, 24 Sep 2007 05:14:30 +0000 (UTC), don@manx.misty.com (Don
Klipstein) wrote:

If you have excessive weight loading on your tires, then they are unsafe
at any pressure - their deformation varies directly with ratio of weight
loading to pressure, and any fatigue effects of that get worse when the
deformation is greater or the when "same deformation" occurs at higher
pressure - excessive weight loading is bad no matter what you do.
Click to expand...

Even with normal weight loading, if one is driving around curves like
speed racer, there is going to be excessive distortion introduced,
reducing tire life.
 
On Sun, 23 Sep 2007 22:39:02 -0700, Gunner Asch
<gunner@NOSPAM.earthlink.net> wrote:

On Sun, 23 Sep 2007 19:42:54 -0700, ChairmanOfTheBored
RUBored@crackasmile.org> wrote:

On Sun, 23 Sep 2007 13:35:15 -0700, Gunner Asch
gunner@NOSPAM.earthlink.net> wrote:

On Sun, 23 Sep 2007 12:10:07 -0700, ChairmanOfTheBored
RUBored@crackasmile.org> wrote:

What DUMB BASTARD that doesn't know a fucking thing about Usenet made
this stupid, cross-posted SHIT?


Evidently it was you.

Gunner


Responses don't count, dipshit. I have to ensure that my post gets read
by the twit that posted across several groups, many of which he may not
even visit or pull headers from. Get a clue.


so you are admitting to being the DUMB BASTARD that doesnt know a
fucking thing about Usenet who made that stupid cross-posted SHIT.

Thank you for playing
Click to expand...
No, you retarded fuck. I directly referred to the original poster, and
if you weren't a fucking illiterate bastard you'd have seen that, and no,
dipshit, it is not a game, so thank you for being the stupid fucktard I
knew you would be.
 
On Mon, 24 Sep 2007 05:18:00 -0400, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

Gunner Asch wrote:

On Sun, 23 Sep 2007 12:10:07 -0700, ChairmanOfTheBored
RUBored@crackasmile.org> wrote:

What DUMB BASTARD that doesn't know a fucking thing about Usenet made
this stupid, cross-posted SHIT?

Evidently it was you.

Gunner


His real name is 'dimbulb', and he morphs more often than he bathes.
Thats why all his posts stink. ;-)

Don't waste your tinme on him, he's as big a loser as Hawkie, and
Sloman.
Click to expand...

Fuck you, TerrellTard!
 
ChairmanOfTheBored wrote:
On Mon, 24 Sep 2007 05:18:00 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:

Gunner Asch wrote:

On Sun, 23 Sep 2007 12:10:07 -0700, ChairmanOfTheBored
RUBored@crackasmile.org> wrote:

What DUMB BASTARD that doesn't know a fucking thing about Usenet made
this stupid, cross-posted SHIT?

Evidently it was you.

Gunner


His real name is 'dimbulb', and he morphs more often than he bathes.
Thats why all his posts stink. ;-)

Don't waste your tinme on him, he's as big a loser as Hawkie, and
Sloman.

Fuck you, TerrellTard!
Click to expand...

Once again: I'm not into queers like you are, dimbulb.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
Rich Grise wrote:
Saturday morning TV is mostly cartoons, yes, but there's one show that's
not a cartoon, but it's still fun:
http://www.beakmansworldtv.com/

It's like Stealth Educational TV - like Mr. Wizard for the 21st century
kid. And they do Real Science.

But today, they said that you can weigh your car by using your tire
pressure. What you do is measure the footprint of each tire, take its
pressure, and then the footprint of the tire times the PSI equals
the number of pounds that the tire is supporting, and their sum is the
weight of the car. (except for the tires themselves, I presume).

But they did the experiment - they measured the footprints of the four
tires on Some very well-preserved Nash Rambler, and their PSI, and did
the arithmetic, and came up with a number that was within 10% of the car's
"official" weight.
Click to expand...
That's correct. But if you change the tire pressure, the footprint
changes as well. The change in footprint isn't linear, being dependent
on sidewall stiffness and other factors.

Well, I'm a little uncomfortable with that. What about the pressure that's
in a tire when it's not on the car? Where does that pressure go? Is that
that 10% fudge factor that they admitted to in the show?

How much does the pressure change when you take a standalone tire, mount
it on the car, and let the car down on it?
Click to expand...
It depends on the change in volume of the tire as the tire's contact
patch flattens out and takes up the vehicles load.

Or do they get around that by saying, "Well, you can ignore that, because
the tire's not supporting any weight". Or is it entirely ( or mostly) due
to the flattening of the bottom of the tire? Does the "bias pressure" (a
term I just made up now, for the pressure that's there when it's not on
the car) get lost below the noise floor?

Thanks,
Rich
Click to expand...
Think about this: I can over or under inflate my tires easily by a
factor of two (or more) without the wheel's bead hitting bottom. The
vehicle's weight didn't change by a factor of two.

Neither their theories nor their tires hold any air.


--
Paul Hovnanian mailto:paul@Hovnanian.com
------------------------------------------------------------------
Experience is the worst teacher. It always gives the test
first and the instruction afterward.
 
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