Do fats works?

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Beable van Polasm

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Jan 12, 2000, 3:00:00 AM1/12/00
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Hi there drivers,

I was thinking about getting some really fat tyres for
my 460 cubic inch Falcon to give it better grip, because
EVERYBODY knows that fat tyres mean better grip. The
local tyre shop has got some tyres that are 30cm wide.
If I shorten the axles a bit and take out the mudguards,
they might fit.

But then I thought "HEY WAITAMINUTE!". If I have fatter
tyres, that would mean that I would have less pressure
on the road, because the car would weigh the same, but
there would be more tyre area on the road. And less
pressure on the road should logically mean LESS GRIP!
So then I was thinking that if I got the skinniest
tyres I could, which are bicycle tyres 1cm wide, then
that would mean maximum pressure and therefore maximum
grip.

Here are my calculations:
Fat tyres:
Contact patch = 30cm * 15cm * 4 = 1800cm^2
Car weight = 1850kg
Grip = 1850 / 1800 = 1.027777777 kg/cm^2

Skinny tyres:
Contact patch = 1cm * 10cm * 4 = 40cm^2
Car weight = 1800 kg (skinny tyres and wheels are lighter!)
Grip = 1800 / 40 = 45 kg/cm^2

SO I WOULD GET OVER FORTY TIMES AS MUCH GRIP WITH
SKINNY TYRES!!!!!!11!

Have I got this right? Has this important information
been covered up by the tyre manufacturers so that they can
sell expensive fat tyres instead of cheap bicycle tyres?
I think in the future drag cars are going to be running
on razor blade tyres to get maximum grip instead of those
monster tyres they are using now!

cheers
beable van polasm
--
I guess this evening I'll have one ethic, and then the other seven
by the end of this academic quarter. Also, I'm allowed to miss two
classes. -- Joe "Crow" Bay
http://members.xoom.com/_______/index.html


Sent via Deja.com http://www.deja.com/
Before you buy.

Leo Sgouros

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Jan 12, 2000, 3:00:00 AM1/12/00
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"Beable van Polasm" <bea...@my-deja.com> wrote in message
news:85gnkb$3bp$1...@nnrp1.deja.com...

Dear Beable
from my hot rod days I remember I had to use a "tall" tire to compensate for
this IANMTU if you KWIM.

Roger Smith

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Jan 12, 2000, 3:00:00 AM1/12/00
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following this, skinny tin lid type tyres would be best
then, say 1mm wide right? that woudlk have to get the most
traction? yeah right.

Norbie

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Jan 12, 2000, 3:00:00 AM1/12/00
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Beable van Polasm <bea...@my-deja.com> wrote in message
news:85gnkb$3bp$1...@nnrp1.deja.com...
>
> Here are my calculations:
> Fat tyres:
> Contact patch = 30cm * 15cm * 4 = 1800cm^2

Hold on a sec, where did this 15cm figure come from? How do you know the
contact patch is 15cm long?

> Car weight = 1850kg
> Grip = 1850 / 1800 = 1.027777777 kg/cm^2
>
> Skinny tyres:
> Contact patch = 1cm * 10cm * 4 = 40cm^2

Again, where did the 10cm come from?

> Car weight = 1800 kg (skinny tyres and wheels are lighter!)
> Grip = 1800 / 40 = 45 kg/cm^2
>
> SO I WOULD GET OVER FORTY TIMES AS MUCH GRIP WITH
> SKINNY TYRES!!!!!!11!

In your dreams!

> Have I got this right?

In a word, no.

Believe it or not, the pressure between the tyre and the road surface is
pretty much the same as the air pressure inside the tyre, regardless of the
size of the tyre or the weight of the vehicle. So if you pump your "fats"
up to 40psi, the pressure between the tyre and the road will be 40psi (or
pretty close to it). This means that the size of the contact patch will
vary according to the pressure in the tyre, if we assume the weight of the
vehicle is constant. Obviously the width of the contact patch is more or
less fixed, so the length will vary.

You can observe this for yourself by doing a simple experiment. You need a
bicycle with a wet rear tyre and some flat dry concrete. Place the bicycle
on the concrete (don't roll it) and lift it off again, observing the wet
print left behind. Now try it again in a different spot but sit on the bike
this time. You will notice that the contact patch is much longer! You can
also experiment with different pressures and a fixed mass, and you will find
that more pressure equals a smaller contact patch.

So that's the major flaw in your equation - you assumed that the size of the
contact patch is fixed for a given size of tyre. And we haven't even
discussed important variables like tyre compound, road surface composition
and temperature, all of which have a significant effect on a tyre's grip.

Norbie.

Charlie

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Jan 12, 2000, 3:00:00 AM1/12/00
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Beable van Polasm wrote:

> Hi there drivers,
>
> I was thinking about getting some really fat tyres for
> my 460 cubic inch Falcon to give it better grip, because
> EVERYBODY knows that fat tyres mean better grip. The
> local tyre shop has got some tyres that are 30cm wide.
> If I shorten the axles a bit and take out the mudguards,
> they might fit.
>

> But then I thought "HEY WAITAMINUTE!". If I have fatter
> tyres, that would mean that I would have less pressure
> on the road, because the car would weigh the same, but
> there would be more tyre area on the road. And less
> pressure on the road should logically mean LESS GRIP!
> So then I was thinking that if I got the skinniest
> tyres I could, which are bicycle tyres 1cm wide, then
> that would mean maximum pressure and therefore maximum
> grip.

The road is not perfectly flat, it has small bumps all over it which the
tyre's deform to as they go over, creating more surface area /
traction... tyres work better when hot because they deform to the road
easier... I think that's the general idea anyway.

lambo

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Jan 12, 2000, 3:00:00 AM1/12/00
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I remember the babblings of a physics teacher going on about wide tyres vs
skinny tyres and the coefficient of friction of two contacting surfaces and
the lateral force required to make them slip being equal for both the skinny
and wide tyres .. we then proved the theory it in an experiment........ the
maths has long since escaped me

Any physics smarty people out there ?


dave


Beable van Polasm wrote in message <85gnkb$3bp$1...@nnrp1.deja.com>...


>Hi there drivers,
>
>I was thinking about getting some really fat tyres for
>my 460 cubic inch Falcon to give it better grip, because
>EVERYBODY knows that fat tyres mean better grip. The
>local tyre shop has got some tyres that are 30cm wide.
>If I shorten the axles a bit and take out the mudguards,
>they might fit.
>
>But then I thought "HEY WAITAMINUTE!". If I have fatter
>tyres, that would mean that I would have less pressure
>on the road, because the car would weigh the same, but
>there would be more tyre area on the road. And less
>pressure on the road should logically mean LESS GRIP!
>So then I was thinking that if I got the skinniest
>tyres I could, which are bicycle tyres 1cm wide, then
>that would mean maximum pressure and therefore maximum
>grip.
>

>Here are my calculations:
>Fat tyres:
>Contact patch = 30cm * 15cm * 4 = 1800cm^2

>Car weight = 1850kg
>Grip = 1850 / 1800 = 1.027777777 kg/cm^2
>
>Skinny tyres:
>Contact patch = 1cm * 10cm * 4 = 40cm^2

>Car weight = 1800 kg (skinny tyres and wheels are lighter!)
>Grip = 1800 / 40 = 45 kg/cm^2
>
>SO I WOULD GET OVER FORTY TIMES AS MUCH GRIP WITH
>SKINNY TYRES!!!!!!11!
>

Michael

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Jan 12, 2000, 3:00:00 AM1/12/00
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Hi...

Roger Smith <ro...@chimo.com.au> wrote in message
news:387BFB49...@chimo.com.au...


> following this, skinny tin lid type tyres would be best
> then, say 1mm wide right? that woudlk have to get the most
> traction? yeah right.

It isn't quite as simple as it seems - the tyre has to be physically strong
enough to hold the car up so odviously a 1mm tyre wouldn't work. I can't
remember the physics of it but as a rough rule of thumb, the wider the tyre,
the softer the compound (read higher co-efficient of friction with the road)
you can get away with while still getting decent life out of them.

That is why the narrower tyres are generally harder compound.

Later...

Michael

Rob

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Jan 12, 2000, 3:00:00 AM1/12/00
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> the lateral force required to make them slip being equal for both the
skinny
> and wide tyres

Then what use are wider tyres?


lambo <la...@primus.com.au> wrote in message
news:MqWe4.18$_Q....@nsw.nnrp.telstra.net...

dubwâ

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Jan 12, 2000, 3:00:00 AM1/12/00
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Rob wrote:
>
> > the lateral force required to make them slip being equal for both the
> skinny
> > and wide tyres
>
> Then what use are wider tyres?

Less flex, making the suspension appear stiffer.
The MaxLoad is higher for bigger tyres.
The compounds used are usually of better and more expensive quality, as
is the "design".

Regards,
Steven
--
- It's dangerous if you don't understand it.
- That's what they told Lindbergh...
But that didn't stop him from inventing the lightbulb.

Rob

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Jan 12, 2000, 3:00:00 AM1/12/00
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yes thats what i thought. but if the force required to make them skid is the
same then whats the point.


harry <haro...@yahoo.com> wrote in message
news:387c88a2$0$19...@motown.iinet.net.au...
> better cornering ?
> "Rob" <robste...@iname.com> wrote in message
> news:387c538e$0$19...@motown.iinet.net.au...


> > > the lateral force required to make them slip being equal for both the
> > skinny
> > > and wide tyres
> >
> > Then what use are wider tyres?
> >
> >

> > lambo <la...@primus.com.au> wrote in message
> > news:MqWe4.18$_Q....@nsw.nnrp.telstra.net...
> > > I remember the babblings of a physics teacher going on about wide
tyres
> vs
> > > skinny tyres and the coefficient of friction of two contacting
surfaces
> > and

> > > the lateral force required to make them slip being equal for both the
> > skinny

Worn-Out Horn

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Jan 12, 2000, 3:00:00 AM1/12/00
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In article <CcTe4.292$4J.1...@nsw.nnrp.telstra.net>,
"Norbie" <turbo...@mail.optusnet.com.au> wrote:

> Believe it or not, the pressure between the tyre and the road surface
> is pretty much the same as the air pressure inside the tyre,
> regardless of the size of the tyre or the weight of the vehicle.
> So if you pump your "fats" up to 40psi, the pressure between the tyre
> and the road will be 40psi (or pretty close to it).

HORSE CRAP! If your car weighs 3000 lbs., all that weight has
to be distributed through the 4 tires. That weight, or pressure
on the road, is not distributed equally since the motor is a
large portion of the weight. Just as a guess, let's say the
weight in the front is 2000 lbs., and the weight in the back
is 1000, and that each rear tire must bear 500 lbs. Regardless
of the width of the tires, each tire must bear 500 lbs. The
narrower the tire, the higher the PSI is for that tire on the
road. Granted, increasing the tire pressure will reduce the
contact patch, which increases the PSI, just like installing
wider tires will decrease the PSI. The larger the contact
patch, the lower the PSI is.

PSI pressure on the road does
not equal the internal tire pressure, unless of course you
install an enourmously wide tire, with low air pressure.
The contact area would have to be huge for a 3000 lb. car
to only have 40 PSI for a tire on the road. Have you ever
let a car's tire roll over your foot? I don't advise it.

Mark Hill

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Jan 12, 2000, 3:00:00 AM1/12/00
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"lambo" <la...@primus.com.au> writes:
> Any physics smarty people out there ?

Any physics smarty people in this newsgroup?

I just like that phrase.

Björn Nyhlén

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Jan 12, 2000, 3:00:00 AM1/12/00
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"Worn-Out Horn" <dan...@my-deja.com> skrev i meddelandet
news:85igkj$cam$1...@nnrp1.deja.com...

A quick calculation with 3000lbs car and 40psi on the road gives 75 in^2
contact patch. Assuming equal tires and even wheight distr. we get 18.75
in^2 per tire. Assuming 5in wide tires we get 3.75 in long contact patches
per tire. Now that seems pretty reasonable doesn't it?

-Björn

Marshall Willenholley

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Jan 12, 2000, 3:00:00 AM1/12/00
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Björn Nyhlén <bjorn.n...@student.lth.se> wrote in message
news:85ij14$hu$1...@news.lth.se...

Ok, deflate the tires to 15 psi and explain how we now hav 15 psi on
the road.

--
Marshall Willenholley
"If I thought it mattered I'd be you"
To reply, change yipee to yahoo.

Steve Bigelow

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Jan 12, 2000, 3:00:00 AM1/12/00
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Marshall Willenholley wrote in message
<_25f4.81$HPg.5...@dca1-nnrp1.news.digex.net>...

>> A quick calculation with 3000lbs car and 40psi on the road gives
>75 in^2
>> contact patch. Assuming equal tires and even wheight distr. we get
>18.75
>> in^2 per tire. Assuming 5in wide tires we get 3.75 in long contact
>patches
>> per tire. Now that seems pretty reasonable doesn't it?

>Ok, deflate the tires to 15 psi and explain how we now hav 15 psi on
>the road.


3000/4=750 per tire

750/15=50 square inches of contact patch.

No, no one said it is/or will remain perfectly linear. If you drop it right
onto the rims, however....you'll have eight little contact
patches.....rather heavily weighted ones, too.

Björn Nyhlén

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Jan 12, 2000, 3:00:00 AM1/12/00
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"> >
> > A quick calculation with 3000lbs car and 40psi on the road gives
> 75 in^2
> > contact patch. Assuming equal tires and even wheight distr. we get
> 18.75
> > in^2 per tire. Assuming 5in wide tires we get 3.75 in long contact
> patches
> > per tire. Now that seems pretty reasonable doesn't it?
> >
> > -Björn

> >
> >
>
> Ok, deflate the tires to 15 psi and explain how we now hav 15 psi on
> the road.
>
> --
> Marshall Willenholley
> "If I thought it mattered I'd be you"
> To reply, change yipee to yahoo.
>
>

Just do the calculations again. Although the contact paches may not be
rectangular in shape like I simplified above.

Chuck Tomlinson

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Jan 12, 2000, 3:00:00 AM1/12/00
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Worn-Out Horn <dan...@my-deja.com> wrote:
> "Norbie" <turbo...@mail.optusnet.com.au> wrote:
>
>> Believe it or not, the pressure between the tyre and the road surface
>> is pretty much the same as the air pressure inside the tyre,
>> regardless of the size of the tyre or the weight of the vehicle.
>> So if you pump your "fats" up to 40psi, the pressure between the tyre
>> and the road will be 40psi (or pretty close to it).
>
>HORSE CRAP!

Actually, Norbie is correct.

> If your car weighs 3000 lbs., all that weight has
>to be distributed through the 4 tires. That weight, or pressure
>on the road,

<Red Alert!> Pressure and weight are two different things!



>is not distributed equally since the motor is a
>large portion of the weight. Just as a guess, let's say the
>weight in the front is 2000 lbs., and the weight in the back
>is 1000, and that each rear tire must bear 500 lbs. Regardless
>of the width of the tires, each tire must bear 500 lbs. The
>narrower the tire, the higher the PSI is for that tire on the
>road.

No. For a fixed weight, as you decrease the width of the tire, you
will increase the length of the contact patch. The *area* of the
contact patch will stay about the same, roughly equal to the weight
on the tire divided by the tire pressure.

>[...] PSI pressure on the road does


>not equal the internal tire pressure,

Contact pressure does not *equal* the tire pressure, because a small
amount of the tire load is carried by the mechanical stiffness of
the sidewall and tread. The vast majority of the tire's load,
however, must be supported by the air pressure in the tire, so
contact patch pressure will be slightly less than tire pressure.

That's for normal tires, BTW. Some so-called run-flat tires have
such stiff sidewalls that they can support most of the tire load
without assistance from air pressure.



>The contact area would have to be huge for a 3000 lb. car
>to only have 40 PSI for a tire on the road.

No. Looks like a good guess at first, though. Guess again?

>Have you ever
>let a car's tire roll over your foot? I don't advise it.

I also don't recommend letting a large adult stand on your foot,
balancing all their weight on one heel. It's about the same thing.
BTW, I know people who've had tires roll over their feet (with cars
attached), without injury.
--
Chuck Tomlinson


Bill Newcomb

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Jan 12, 2000, 3:00:00 AM1/12/00
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In article <xzcn1qb...@rodan.syr.edu>,
Rich Holmes <rsholme...@mailbox.syr.edu> wrote:

> "Marshall Willenholley" <MWille...@yipee.com> writes:
>
> > Ok, deflate the tires to 15 psi and explain how we now hav 15 psi on
> > the road.
>
> Better yet, just take all the air out of the tires and leave the car
> hovering in midair.

Oh, nice try, Mr. PhD in Physics, but we're not that easily fooled.

1) There's no such thing as a complete vacuum, so you can't take *all*
the air out of the tires.

2) Even if you did, the weight of the air above the car (out to the
stratosphere) is *much* larger that that beneath it, and hence the car
would be pushed to the ground. C'mon, this is like high school
cafeteria physics.

--
nu...@best.com | "When naked, a transaction is retried when
| bus time is available." --USB 1.1 Spec

Martin Harvey

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Jan 12, 2000, 3:00:00 AM1/12/00
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Worn-Out Horn wrote:
>
> The contact area would have to be huge for a 3000 lb. car
> to only have 40 PSI for a tire on the road.

Not really... about 75 square inches, which is about 18 square inches
per tyre, which is not very much at all ... about the area of your palm.

MH.

--
Martin Harvey. mar...@pergolesi.demon.co.uk
http://www.pergolesi.demon.co.uk

The Usenet Oracle has pondered your question deeply. Your question
was: Will your answer to this question be in the negative?
And in response, thus spake the Oracle: Memory fault. Core dumped.

Martin Harvey

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Jan 12, 2000, 3:00:00 AM1/12/00
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lambo wrote:
>
> I remember the babblings of a physics teacher going on about wide tyres vs
> skinny tyres and the coefficient of friction of two contacting surfaces and
> the lateral force required to make them slip being equal for both the skinny
> and wide tyres .. we then proved the theory it in an experiment........ the
> maths has long since escaped me
>
> Any physics smarty people out there ?
>

All other things being equal yes. The crucial assumption here is that
static friction is proportional to the pressure between the tyre and the
road.

Steve K

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Jan 12, 2000, 3:00:00 AM1/12/00
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Bill Newcomb <nu...@best.com> wrote in message
news:387d043b$0$2...@nntp1.ba.best.com...

> Oh, nice try, Mr. PhD in Physics, but we're not that easily fooled.
>
> 1) There's no such thing as a complete vacuum, so you can't take *all*
> the air out of the tires.

Who said vacuum? This thread has been throwing around gauge pressure the
whole time. 0 psig is very, very easily achievable.

> 2) Even if you did, the weight of the air above the car (out to the
> stratosphere) is *much* larger that that beneath it, and hence the car
> would be pushed to the ground. C'mon, this is like high school
> cafeteria physics.

Were you even listening?

It comes down to this:

* Pressure = Force / Area
We don't care about the air pressure in the tire. This is pressure between
the tire and road. Force is the weight of the car--a.k.a. the mass of the
car as gravity acts upon it.

* Force = Mass * Acceleration
Acceleration = Force / Mass

...the force the tire can exert (at most) on the road surface, which may or
may not result in acceleration, is the weight of the car times a constant of
static friction.

In an ideal world of high-school physics (above), the tire may exert the
same maximum force upon the road surface whether the tire is one inch or 100
inches wide. As the tire gets wider, pressure decreases. But it doesn't
matter.

The reason a wider tire, with a larger contact patch (and therefore
decreased pressure on the road surface) works is because tires are adhesive
and deformable. Other things being equal, a foot of masking tape sticks
better than an inch. And yes, the wider tire's compound is likely to be
more adhesive than the skinny, economy-minded version...

harry

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Jan 13, 2000, 3:00:00 AM1/13/00
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better cornering ?
"Rob" <robste...@iname.com> wrote in message
news:387c538e$0$19...@motown.iinet.net.au...
> > the lateral force required to make them slip being equal for both the
> skinny
> > and wide tyres
>
> Then what use are wider tyres?
>
>
> lambo <la...@primus.com.au> wrote in message
> news:MqWe4.18$_Q....@nsw.nnrp.telstra.net...
> > I remember the babblings of a physics teacher going on about wide tyres
vs
> > skinny tyres and the coefficient of friction of two contacting surfaces
> and
> > the lateral force required to make them slip being equal for both the
> skinny
> > and wide tyres .. we then proved the theory it in an experiment........
> the
> > maths has long since escaped me
> >
> > Any physics smarty people out there ?
> >
> >

Norbie

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Jan 13, 2000, 3:00:00 AM1/13/00
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Worn-Out Horn <dan...@my-deja.com> wrote in message

news:85igkj$cam$1...@nnrp1.deja.com...
> In article <CcTe4.292$4J.1...@nsw.nnrp.telstra.net>,
> "Norbie" <turbo...@mail.optusnet.com.au> wrote:
>
> > Believe it or not, the pressure between the tyre and the road surface
> > is pretty much the same as the air pressure inside the tyre,
> > regardless of the size of the tyre or the weight of the vehicle.
> > So if you pump your "fats" up to 40psi, the pressure between the tyre
> > and the road will be 40psi (or pretty close to it).
>
> HORSE CRAP!

Not at all. Did you try the experiment I proposed? Didn't think so.

> If your car weighs 3000 lbs., all that weight has
> to be distributed through the 4 tires. That weight, or pressure

> on the road, is not distributed equally since the motor is a


> large portion of the weight. Just as a guess, let's say the
> weight in the front is 2000 lbs., and the weight in the back
> is 1000,

I'd hate to drive a car with weight distribution like that, but OK! :-)

> and that each rear tire must bear 500 lbs. Regardless
> of the width of the tires, each tire must bear 500 lbs.

Right so far.

> The narrower the tire, the higher the PSI is for that tire
> on the road.

*Bzzzzt* This is only true *if* we assume the tyre doesn't deform when a
load is placed on it. Have you ever watched a tyre change shape as you take
the weight off it with a jack? This shows us that the size of the contact
patch is *not* fixed for a given tyre width. Obviously the pressure between
the road and the tyre is related not only to the weight it's supporting, but
the size of the contact patch.

> Granted, increasing the tire pressure will reduce the
> contact patch, which increases the PSI, just like installing
> wider tires will decrease the PSI. The larger the contact
> patch, the lower the PSI is.

But in the previous paragraph you were assuming the size of the contact
patch is fixed! And now it's not? Perhaps you're a little confused.

> PSI pressure on the road does

> not equal the internal tire pressure, unless of course you
> install an enourmously wide tire, with low air pressure.

> The contact area would have to be huge for a 3000 lb. car
> to only have 40 PSI for a tire on the road.

Not huge at all. Someone else in this thread has already done the
calculations.

> Have you ever
> let a car's tire roll over your foot? I don't advise it.

It's not advisable at all, but I fail to see what this has to do with it?

Norbie.

Norbie

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Jan 13, 2000, 3:00:00 AM1/13/00
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Rob <robste...@iname.com> wrote in message
news:387c94a3$0$19...@motown.iinet.net.au...

> yes thats what i thought. but if the force required to make them skid is
the
> same then whats the point.

There are several reasons, but one of them is that a wider tyre is less
susceptible to localised overheating of the tyre compound, which leads to
the breakdown of the tyre compound and ultimately loss of grip. Basically,
the rubber melts and your tyre is riding on a layer of molten rubber, which
obviously doesn't grip too well, and the tyre starts to "skid". Of course
most of this molten rubber gets left behind on the road - hey presto,
"skidmarks"!

A wider tyre will always have a shorter contact patch for a given vehicle
weight and inflation pressure, which means each point on the tyre will be in
contact with the road for a shorter amount of time, which means it is less
likely to overheat when placed under extreme loads.

Norbie.

Beable van Polasm

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Jan 13, 2000, 3:00:00 AM1/13/00
to
In article <EN7f4.61$FW....@nsw.nnrp.telstra.net>,

"Norbie" <turbo...@mail.optusnet.com.au> wrote:
>
> Rob <robste...@iname.com> wrote in message
> news:387c94a3$0$19...@motown.iinet.net.au...
> > yes thats what i thought. but if the force required to make them
> > skid is the same then whats the point.

Well because they COST MORE! It's the tyre manufacturers'
conspiracy. They trick people into liking inferior fat
tyres, even though skinny tyres can be mathematically
proven to have MORE GRIP and thus better handling.

> There are several reasons, but one of them is that a wider tyre is
> less
> susceptible to localised overheating of the tyre compound, which leads
> to
> the breakdown of the tyre compound and ultimately loss of grip.
> Basically,
> the rubber melts and your tyre is riding on a layer of molten rubber,
> which
> obviously doesn't grip too well, and the tyre starts to "skid". Of
> course
> most of this molten rubber gets left behind on the road - hey presto,
> "skidmarks"!

Yes and there might be some "skidmarks" on the road too!


> A wider tyre will always have a shorter contact patch for a given
> vehicle
> weight and inflation pressure, which means each point on the tyre will
> be in
> contact with the road for a shorter amount of time, which means it is
> less
> likely to overheat when placed under extreme loads.

Ok, I understand all that, but think about this:
Imagine you have a standard 16 ton weight. If you
put four stainless steel spikes on the bottom,
one on each corner, then put it on a road, the
spikes will give it lots of grip on the road and
you won't beable to move it.

+------------+
/ /|
/ / |
+------------+ |
| | +
| 16 TONS | /|
| |/
+------------+
| | <-- SPIKES
IMPOSSIBLE TO MOVE!

Now put it on a large stainless steel sheet,
and the sheet will act like a sled and you can
move the sixteen ton weight around. The reason
why the spikes give more grip is because they
have LESS SURFACE AREA, and the same weight,
so therefore they provide MORE PRESSURE on the
road and MORE GRIP. But spikes are spiky, and
so they aren't much good for automotive
applications.

+------------+
/ /|
/ / |
+------------+ |--+
| | + /
| 16 TONS | / / <-- STAINLESS STEEL SHEET
| |/ / EASY TO MOVE!
/+------------+ / BUT NO DIRECTIONAL STABILITY!
+---------------+

So if we take off the spikes, and
put some steel wheels on the sixteen ton weight,
then it can roll along.

+------------+
/ /|
/ / |
+------------+ |
| | +
| 16 TONS | /O
| |/
+------------+
O O <-- WHEELS

In order to get the most pressure on the road, we
want to have the wheels as narrow as possible, so
the wheel should look like this in cross section:

~
~
~
| <-- SIXTEEN TON WEIGHT
|
~~~---------+
| | |
| ^ |
| / \ |
+-< >-+ <-- AXLE
\ / <-- WHEEL
v
| <-- REALLY SHARP PART OF WHEEL FOR MAXIMUM GRIP!

These new "RazorBlade Tyres" provide maximum grip because
the blades cut into the road surface and stop the vehicle
from going sideways AT ALL! They also provide maximum grip
to stop wheel spin or skidding under massive acceleration
or decceleration because of the same reason, the wheels
cut into the road and so they can't spin or skid because
they have MAXIMUM GRIP! Because the wheels are made of
STEEL they give Excellent Heat Dissipation and maximum
pressure on the road. Flat tyres will be a thing of the
past! I don't know why nobody thought of this before
except if it's a big conspiracy amongst the tyre manufacturers
to make sure that everybody keeps buying really expensive fat
tyres instead of using superior CHEAPER technology, namely
RAZOR BLADE TYRES!

cheers
Beable van Polasm
--
Beable Industries - For a BETTER Tomorrow, Today!

Chuck Tomlinson

unread,
Jan 13, 2000, 3:00:00 AM1/13/00
to
"Norbie" <turbo...@mail.optusnet.com.au> wrote:
>
>A wider tyre will always have a shorter contact patch for a given vehicle
>weight and inflation pressure, which means each point on the tyre will be in
>contact with the road for a shorter amount of time, which means it is less
>likely to overheat when placed under extreme loads.

And, as a racer friend of mine pointed out, wider tires also have
more surface area to dissipate heat generated at the contact patch.
--
Chuck Tomlinson

Maso

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Jan 13, 2000, 3:00:00 AM1/13/00
to

Beable van Polasm <bea...@my-deja.com> wrote in message

news:85jk8l$70d$1...@nnrp1.deja.com...


> In article <EN7f4.61$FW....@nsw.nnrp.telstra.net>,
> "Norbie" <turbo...@mail.optusnet.com.au> wrote:
> >

snip -some good information on tyre choice-


> These new "RazorBlade Tyres" provide maximum grip because
> the blades cut into the road surface and stop the vehicle
> from going sideways AT ALL! They also provide maximum grip
> to stop wheel spin or skidding under massive acceleration
> or decceleration because of the same reason, the wheels
> cut into the road and so they can't spin or skid because
> they have MAXIMUM GRIP! Because the wheels are made of
> STEEL they give Excellent Heat Dissipation and maximum
> pressure on the road. Flat tyres will be a thing of the
> past! I don't know why nobody thought of this before
> except if it's a big conspiracy amongst the tyre manufacturers
> to make sure that everybody keeps buying really expensive fat
> tyres instead of using superior CHEAPER technology, namely
> RAZOR BLADE TYRES!
>
> cheers
> Beable van Polasm
> --
> Beable Industries - For a BETTER Tomorrow, Today!
> http://members.xoom.com/_______/index.html
>
>


That may well be the case Mr v P, but fats look much cooler than bicycle
tires on cars (especially on falcons), so you have a choice: gripiness
versus dorkiness.

Captains of Industry such as yourself understand that many people would
prefer coolness over functionality (eg the Fonz v. Richie Cunningham, red
smarties v. brown smarties)

Maybe you could counter-act the loss of grip from fats with a .....*Warning
SPOILER Warning*....


v
v
v
v
v
v
v
v
v
v
v
v
v
v
v
v
v
v
v

...spoiler on the boot of your car.


I hope you resolve your tyre dilemma and are back on the road soon.
Charles

David DeLaney

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Jan 13, 2000, 3:00:00 AM1/13/00
to
Worn-Out Horn <dan...@my-deja.com> writes:
>Have you ever
>let a car's tire roll over your foot? I don't advise it.

Why, yes.

It was a Volkswagen.

Nothing much happened.

Dave "guess they really -are- light enough to float" DeLaney
--
\/David DeLaney d...@panacea.phys.utk.edu "It's not the pot that grows the flower
It's not the clock that slows the hour The definition's plain for anyone to see
Love is all it takes to make a family" - R&P. VISUALIZE HAPPYNET VRbeable<BLINK>
http://panacea.phys.utk.edu/~dbd/ - net.legends FAQ/ I WUV you in all CAPS! --K.

David DeLaney

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Jan 13, 2000, 3:00:00 AM1/13/00
to
nu...@best.com (Bill Newcomb) writes:
>Rich Holmes <rsholme...@mailbox.syr.edu> wrote:
>> "Marshall Willenholley" <MWille...@yipee.com> writes:
>>
>> > Ok, deflate the tires to 15 psi and explain how we now hav 15 psi on
>> > the road.
>>
>> Better yet, just take all the air out of the tires and leave the car
>> hovering in midair.
>
>Oh, nice try, Mr. PhD in Physics, but we're not that easily fooled.
>
>1) There's no such thing as a complete vacuum, so you can't take *all*
>the air out of the tires.

Well, you -can- move it all -out- of the tires and have it sitting next to
them. (Perhaps supporting a bee.) Injecting water, or Cool Whip, until the
tire is full is one way to drive the air out. (Injecting Hammond posts
would be another.)

>2) Even if you did, the weight of the air above the car (out to the
>stratosphere) is *much* larger that that beneath it, and hence the car
>would be pushed to the ground. C'mon, this is like high school
>cafeteria physics.

But if the air is spherically symmetric, the pressure in any given -direction-
is zero! (Which it's not, quite; there's a residual of about 15 #/in^2 here,
less where prohibited.) And you've failed to take into account the atmosphere
to each -side- of the car, which a simple mental picture reveals there's _more_
of than there is going straight up.

Dave "it's surprising cars don't get squoze into outer space the moment they're
made, actually" DeLaney

Kasper Kowalski

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Jan 13, 2000, 3:00:00 AM1/13/00
to

Beable van Polasm <bea...@my-deja.com> wrote in message
news:85jk8l$70d$1...@nnrp1.deja.com...

> Well because they COST MORE! It's the tyre manufacturers'


> conspiracy. They trick people into liking inferior fat
> tyres, even though skinny tyres can be mathematically
> proven to have MORE GRIP and thus better handling.

even mathematically you can show that a wider tyre will have more grip under
load once you factor in heat disipation.

<snip bizarre rant about using razor blades for tyres>

you forgot one crucial thing, friction coefficient. the friction coeffient
of a spike on a road is much greater than the same spike on a smooth sheet
of steel. friction is a property of two surfaces.

KK

Worn-Out Horn

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Jan 13, 2000, 3:00:00 AM1/13/00
to
Norbie,

When I first read your post, what you were saying sounded
really absurd. I didn't think you knew what you were
talking about. After reading the first reply to my post
yesterday, and after thinking about it more, I wanted to
eat my words and apologize. I didn't get a chance then,
so I'm doing it now. I'm sorry for saying you were full
of crap.

> In article <CA7f4.47$FW....@nsw.nnrp.telstra.net>,

> > Have you ever
> > let a car's tire roll over your foot? I don't advise it.
>

> It's not advisable at all, but I fail to see what this has to do with
it?
>
> Norbie.
>
>

harry

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Jan 13, 2000, 3:00:00 AM1/13/00
to
It isn't. You have a larger contact area with the road so it takes a larger
amount of force to lose traction. (Provided you have a similar rubber
compound and tyre pressure. )
If you ever drove a 351 XA on factory tires you'll know what I mean. :)

"Rob" <robste...@iname.com> wrote in message
news:387c94a3$0$19...@motown.iinet.net.au...
> yes thats what i thought. but if the force required to make them skid is
the
> same then whats the point.
>
>

> harry <haro...@yahoo.com> wrote in message
> news:387c88a2$0$19...@motown.iinet.net.au...
> > better cornering ?

> > "Rob" <robste...@iname.com> wrote in message

Kasper Kowalski

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Jan 13, 2000, 3:00:00 AM1/13/00
to

harry <haro...@yahoo.com> wrote in message
news:387dbd09$0$19...@motown.iinet.net.au...

> It isn't. You have a larger contact area with the road so it takes a
larger
> amount of force to lose traction. (Provided you have a similar rubber
> compound and tyre pressure. )
> If you ever drove a 351 XA on factory tires you'll know what I mean.

not quite. there may be a larger area, but the force exerted per unit area
is lower. total friction is the same for both wide and narrow tyres of the
same compound.

KK

harry

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Jan 13, 2000, 3:00:00 AM1/13/00
to

"Worn-Out Horn" <dan...@my-deja.com> wrote in message
news:85igkj$cam$1...@nnrp1.deja.com...
> In article <CcTe4.292$4J.1...@nsw.nnrp.telstra.net>,

> The contact area would have to be huge for a 3000 lb. car

> to only have 40 PSI for a tire on the road. Have you ever


> let a car's tire roll over your foot? I don't advise it.
>

I did and would highly recomend it to anyone.
If you don't have the guts to do it with normal shoes try it with steel caps
first. The most I've tried it with was a 3.5T forklift with solid tires,
with the steel caps of course. :-)

M. Pu

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Jan 13, 2000, 3:00:00 AM1/13/00
to
Very correct. Surface area does not affect the frictional coefficient.
Anyone who has taken physics would know. One advantage of a wider tire,
simple would be it last longer and makes the car look more aggressive.

Marshall Willenholley

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Jan 13, 2000, 3:00:00 AM1/13/00