On 29/06/18 09:41, Andy Burns wrote:
dennis@home wrote:

A flat will change by more than 0.5%

what aspect of it?

as shown empirically by another poster.

who, where?Â* I might have missed it ...


well I think he got 0.8% which triggered his warning system

What he didn get was 5% which is what you might expect from the 'radius'
change


--
€œSome people like to travel by train because it combines the slowness of
a car with the cramped public exposure of €¨an airplane.€�

Dennis Miller

On Fri, 29 Jun 2018 09:33:25 +0100, The Natural Philosopher
wrote:

snip

Just shows that a 27 year old gorl is completely unable to have a basic
comprehension of engineering anmd mechanical sciences just as much as
her benighted stupid dad.

Aww bless. I best she's made fewer online typos in her life than you
made in this one post!

So, when are you going to concede that many of us had it right and you
are still in left brainer denial?

Do you now accept the answer to your question is 'yes', 'an
underinflated tyre does change it's circumference' ... for the
purposes of iTPMS specifically (even if you still can't understand
how)?

Cheers, T i m

Jeff wrote:

Andy Burns wrote:

I can drop the pressure back to 31 and measure the drop of the axle

Yes please.

centre of wheel vertically to ground, 320mm vs 315mm

"Andy Burns" wrote in message
...
Jeff wrote:

Andy Burns wrote:
I can drop the pressure back to 31 and measure the drop of the axle

Yes please.

centre of wheel vertically to ground, 320mm vs 315mm



Wodney seems to have really excelled himself this time around.

He's even got people changing the air pressure in their tyres and doing
measurements.


michael adams

....

On 29/06/18 10:36, Andy Burns wrote:
Jeff wrote:

Andy Burns wrote:
I can drop the pressure back to 31 and measure the drop of the axle

Yes please.

centre of wheel vertically to ground, 320mm vs 315mm



Surprisingly low. But greater than the % RPM change you measured isn't it?

1.5% instead of what you measured...0.4%.



--
"I guess a rattlesnake ain't risponsible fer bein' a rattlesnake, but ah
puts mah heel on um jess the same if'n I catches him around mah chillun".

The Natural Philosopher wrote:

I say its insiginicant in terms of ordinary measurements. You beed veruy
careful speed monitoring to detecte it - a simple exoeriment wont.

Yes, my 50mph test was pretty crude, hardly controlled conditions, I
choose a road that is pretty straight, but it isn't entirely level, runs
were in different directions, there's other traffic on the road, the
software takes a fraction of a second to readout the speed of each wheel
in turn, etc.

It might be fun to paint lines all over my tyres, have an outrigger
slow-mo camera pointing at them and sneak into the test track up the A5,
but I don't think MIRA would be too impressed.

My thesis has always been to try and illustrate the erroneous thinking
of those who think in terms of radius rather than circmference.

Nobody is saying it's the real radius, or the real circumference, but if
you've got a known rate of rotation over a known distance travelled that
does let you derive an "effective radius" or "rolling circumference"

They use those terms because they *know* it's not real, it's a nod
towards the lies of O-Level physics with granite wheels on a granite
road, rather than steel and rubber on tarmac, which we all realise will
deform and slip and squirm as they rotate, even if only a little, and
they'll do that more when underinflated.

The Natural Philosopher wrote:

well I think he got 0.8% which triggered his warning system

If you mean me, it was 0.4% speed change (I haven't seen actual numbers
from anyone else, but my killfile does hide whole sub-threads once
certain people contribute to them).

What he didn get was 5% which is what you might expect from the 'radius'
change

My radius change was 1.5%

michael adams wrote:

Wodney seems to have really excelled himself this time around.

As I hinted just now, certain people (and any responses to them) don't
get seen here ...

The Natural Philosopher wrote:

Surprisingly low.

255/35R19 tyres, so not very "tall" to start with.

But greater than the % RPM change you measured isn'tÂ* it?
1.5% instead of what you measured...0.4%.

Yep.

Tim Streater wrote:

What I'm discounting is a *big* change
in circumference because the axle is "closer to the road"

Well, my axle is 5mm closer to the road (when stationary, who know how
much centrifugal [let's not have *that* discussion] force negates that
when moving?)

or because somehow circumference "disappears".

With the crossed diagonals of the steel belts

https://www.honestjohn.co.uk/media/4320675/tyre_cutaway_630x432.jpg

when the pressure is lowered, the sidewalls will bulge more, which will
pull on the circumference because the steel strands are only contained
in rubber ...

On 29/06/18 11:17, Andy Burns wrote:
The Natural Philosopher wrote:

I say its insiginicant in terms of ordinary measurements. You beed
veruy careful speed monitoring to detecte it - a simple exoeriment wont.

Yes, my 50mph test was pretty crude, hardly controlled conditions, I
choose a road that is pretty straight, but it isn't entirely level, runs
were in different directions, there's other traffic on the road, the
software takes a fraction of a second to readout the speed of each wheel
in turn, etc.

It might be fun to paint lines all over my tyres, have an outrigger
slow-mo camera pointing at them and sneak into the test track up the A5,
but I don't think MIRA would be too impressed.

My thesis has always been to try and illustrate the erroneous thinking
of those who think in terms of radius rather than circmference.

Nobody is saying it's the real radius,

Oh they are. They define that as minimum axle to road distance.

or the real circumference,

Yes, I am.

Circvmference is putting a tape measure round the loaded tyre. It has a
definite meaning

but if
you've got a known rate of rotation over a known distance travelled that
does let you derive an "effective radius" or "rolling circumference"


Which is the tape measure circumference.

They use those terms because they *know* it's not real, it's a nod
towards the lies of O-Level physics with granite wheels on a granite
road, rather than steel and rubber on tarmac, which we all realise will
deform and slip and squirm as they rotate, even if only a little, and
they'll do that more when underinflated.

But they dont change their circumference by anthying more than
elasticity accounts for.





--
"When a true genius appears in the world, you may know him by this sign,
that the dunces are all in confederacy against him."

Jonathan Swift.

On 28/06/2018 21:24, Andy Burns wrote:


As there was nothing on telly tonight, I used my OBD cable to log the
four wheel speed sensors over a straight section of road with cruise
control set to 50mph, which was measured by VCDS as 77.6kph then let
some pressure out of the right rear, turned around, rinse and repeat
until the TPMS triggered.

Starting at 39psi the right rear was on average 0.1kph slower than the
other three wheels, it triggered after letting it down to 31psi by which
time it was on average 0.2kph faster than the other three wheels.

[snip]
You know what, I almost did that myself out of pure curiosity. I know
that iTPMS works because I had it trigger when I had a leaky, corroded
wheel rim, and I was *almost* curious enough to break out VCDS :-)

On Fri, 29 Jun 2018 11:39:41 +0100, Andy Burns wrote:

Well, my axle is 5mm closer to the road (when stationary, who know how
much centrifugal [let's not have *that* discussion] force negates that
when moving?)

I'll inject facts into the handwaving fest:-)

A diagonally belted tire has 5% more travel per rotation at 180km/h than at
60km/h, a radially belted tire 1% more.

This from the German Wiki page on the subject "Abrollumfang".

The article also contains the words "the dynamic rolling radius under load is
greater than the distance from the wheel middle to the road r sub(s)." and a
formula I can't be arsed to transcribe, but I'll toss in

r sub(0): unloaded wheel radius
r sub(s): static radius
r sub(D): dynamic radius

https://de.wikipedia.org/wiki/Abrollumfang


Thomas Prufer

On 29/06/2018 11:32, Tim Streater wrote:


And since as Den so helpfully points out, this is what actually
happens, we conclude that the circumference does not "shrink".


Still twisting what I said I see.
You can't be trusted with anything you say.

You get a lot of it wrong and lie about most of the rest AFAICS.

On 29/06/2018 11:40, The Natural Philosopher wrote:

8

Which is the tape measure circumference.

TNP is still stuck in his closed mind..
it is not the tape measure distance where you said you can put a tape
measure around and measure it.
It changes with speed to start with and other things that cars do when
driving.


They use those terms because they *know* it's not real, it's a nod
towards the lies of O-Level physics with granite wheels on a granite
road, rather than steel and rubber on tarmac, which we all realise
will deform and slip and squirm as they rotate, even if only a little,
and they'll do that more when underinflated.

But they dont change their circumference by anthying more than
elasticity accounts for.

Elasticity in which bit?

TNP won't answer because he knows I am right so he will maintain his
killfile.
Someone else that you can't trust on this newsgroup.

On 29/06/2018 11:39, Andy Burns wrote:
Tim Streater wrote:

What I'm discounting is a *big* change
in circumference because the axle is "closer to the road"

Well, my axle is 5mm closer to the road (when stationary, who know how
much centrifugal [let's not have *that* discussion] force negates that
when moving?)

It negates it quite a lot..
I had a puncture and my front tyre went flat over a couple of hundred
yards in the roadworks on the M6. Rather than stop I continued to drive
for three miles to the end of the road works so I could get on the hard
shoulder.
When I got the tyre replaced there was no wear on the inside to show it
had been rubbing but the hole couldn't be fixed.
The car drove fine.
The only reason I knew it had gone was the TPMS (with pressure sensors)
told me.
I might have noticed if there had been a big bang and I had braked by
mistake.
Not that I recommend doing 50 mph on a flat tyre.


The other flat I had on the M6 was in the rear tyre when I ran over
something in the dark, that split the tyre and dented the rim.
After I pulled up on the hard shoulder there were about another 6 cars
pull up near me all with one or more flats.

I haven't had a flat since but there is always the chance.
There is no spare on the latest car nor anywhere to put one so the AA
can fix it next time.

On 29/06/2018 11:29, Andy Burns wrote:
The Natural Philosopher wrote:

Surprisingly low.

255/35R19 tyres, so not very "tall" to start with.

But greater than the % RPM change you measured isn'tÂ* it?
1.5% instead of what you measured...0.4%.

Yep.


It might be but unless you can measure it under the dynamic conditions
it is just a guess.
I think it would be hard to get an accurate measurement while driving
and a rolling road isn't going to help either.

I don't suppose you have a laser you can exactly centre on the wheel and
suspend a measure down from the wheel arch with a slow mo camera to
record what actually happens? Not serious BTW.

dennis@home wrote:

There is no spare on the latest car nor anywhere to put one

I bought a car like that once ... never again. I think we have to
accept that manufacturers are going to fit space savers, but the gunge
really isn't worth having if you do motorway miles

dennis@home wrote:

I don't suppose you have a laser you can exactly centre on the wheel and
suspend a measure down from the wheel arch with a slow mo camera

Neither have I got a section of glass road with an array of high speed
cameras underneath it to record what happens to an underinflated tyre
"rolling" along it

In article ,
Andy Burns wrote:
dennis@home wrote:

There is no spare on the latest car nor anywhere to put one

I bought a car like that once ... never again. I think we have to
accept that manufacturers are going to fit space savers, but the gunge
really isn't worth having if you do motorway miles

Just wondering how often you've used the spare? Actually *had* to?

At a spares day with my Rover car club, I bought a beautiful spare from a
car which had been written off. Obviously for show, as the lettering on
the tyre had been painted in using white. And the tyre perfect - although
not the same make as mine. I think in the mid 90s. Never been used. ;-)

I have had slow punctures, but never so bad it couldn't be pumped up and
driven to have it fixed.

--
*If you try to fail and succeed, which have you done? *

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman wrote:

Andy Burns wrote:

I bought a car like that once ... never again. I think we have to
accept that manufacturers are going to fit space savers, but the gunge
really isn't worth having if you do motorway miles

Just wondering how often you've used the spare? Actually *had* to?

Three or four times in 7 years, other times I could top-up the tyre and
carry on, the one time the gunge let me down the tyre was completely
destroyed on a motorway, so that turned into a wasted half a day getting
recovered to a garage that had a suitable tyre in stock.

Most tyre places seem to have cut down what they keep in stock to just
"popular" sizes, so you have to order tyres, fair enough they can get
them next day from the wholesaler, but people really hate you sticking
to 50 on a motorway.

I have had slow punctures, but never so bad it couldn't be pumped up and
driven to have it fixed.

Some you'd get away with pumping it up, driving from home to a local
garage to get it fixed, but you wouldn't want to do a long journey on it.

On Fri, 29 Jun 2018 11:32:57 +0100, Tim Streater
wrote:

snip

Various people here have talked about that, with a flat, the axle is
much closer to the road.

No?!

Well, so it is, by almost the whole distance
from where the tread starts down to the tire rim.

Yes, to make that easier for some to understand let's call that 'the
height of the tire wall (you left brained artists do have a strange
way of looking at mechanical things).

That's prolly about a
third, say 30%, and consequently, people have been trying to imply that
30% of the circumference must disappear too.

Where has anyone 'implied' such a thing, apart from in your head?

Well it would need to,
otherwise the wheel and tire would rotate at a different rates and the
tire would disintegrate.

What are you babbling on about now ffs?

And since as Den so helpfully points out, this is what actually
happens, we conclude that the circumference does not "shrink".

Brilliant. The people who actually understand what is going on *know*
that it is in fact exactly what does happen ... and for reasons you
would never be able to understand. ;-(

Cheers, T i m

On Fri, 29 Jun 2018 13:57:07 +0200, Thomas Prufer
wrote:

On Fri, 29 Jun 2018 11:39:41 +0100, Andy Burns wrote:

Well, my axle is 5mm closer to the road (when stationary, who know how
much centrifugal [let's not have *that* discussion] force negates that
when moving?)

I'll inject facts into the handwaving fest:-)

I'm not sure it will make any difference Tomas as 'some people' don't
believe the facts, imperial evidence (millions of cars with iTPMS) and
the 'experts'.

They would prefer (if ever) to come to the exact same conclusion
themselves but shroud it very carefully in a desperate attempt to make
it look like they understood it all along and thinking they can hide
the *fact* they are indeed 'stupid and arrogant tw*ts'. ;-)

A diagonally belted tire has 5% more travel per rotation at 180km/h than at
60km/h, a radially belted tire 1% more.

So, that's because of the pantographing effect (like the dragster
drive wheel I linked to ages ago) as it is spun up, opposite to that
of a deflation (or course).

This from the German Wiki page on the subject "Abrollumfang".

The article also contains the words "the dynamic rolling radius under load is
greater than the distance from the wheel middle to the road r sub(s)." and a
formula I can't be arsed to transcribe, but I'll toss in

;-)

r sub(0): unloaded wheel radius
r sub(s): static radius
r sub(D): dynamic radius

The left brainers will 'get' the direct stuff but won't get the stuff
that requires some imagination.

https://de.wikipedia.org/wiki/Abrollumfang

Thanks for trying though. ;-)

Cheers, T i m

"T i m" wrote in message
...
On Fri, 29 Jun 2018 10:00:30 +1000, "Jeff" wrote:



"T i m" wrote in message
. ..
On Fri, 29 Jun 2018 06:43:35 +1000, "Jeff" wrote:



"T i m" wrote in message
m...

Bingo.

I was walking round the park with our daughter earlier and I gave her
the nutshell iTPMS overview and asked her how she thought it might
work ... how the circumference could become shorter for the iTPMS to
'sense' the increased RPM.

"As the tyre gets flatter it spreads more and that makes the
circumference shorter and so the revs higher?"

Not convinced and that summary makes no sense either.

Then come up with a more credible one?

I prefer to measure, not speculate.

Come up with the measurements then?

As I said, not possible, because while my car has ABS,
the wheel rotation rate of the individual wheels isnt
displayed on the OBD2 data.

the tyre 'spread more' as it gets flatter and why would the
circumference
get shorter even if it did

What part of 'pantographing' don't you get OOI?

I've never been convinced by your pantograph line.

It's not mine, it's what those people who know know.

The steel belts arent panto graphs.

Ok. The belts are woven between the beads in a ziz-zag, working their
way round the tyre till they join up again. these cross at roughly 90
degrees and form a parallelogram.

But they arent joined where they cross like those pop rivet setters.

When you load a tyre that causes it
to widen, it has to get the material from somewhere and because the
rubber is 'bound' to some degree by the bets, the only way that can
happen is some foreshortening of the length of the tread from where
it's distorted.

Never been convinced about that either. Yes, when the tyre pressure
is reduced a bit, there is more tyre in contact with the road, and the
walls clearly bulge more, but there isnt any evidence that there is
more tyre in contact with the road across the tyre itself.

What do you have as an alternative explanation?

As I said, I prefer to measure and then, when that measurement does
show that the wheel rotation rate does vary with the circumference
and not with the distance between the axle and the road, look for
an explanation of why it happens like that.

Have you ever seen one of those expanding pop rivet guns ... of the
joke boxing glove on an expanding arm?

When those things get wider they get shorter.

Yes, but the steel belts in car tyres are nothing like that.

They are everything like that (but maybe you just don't realise it)?

There is no pivot at each crossing point like there is with the pop rivet
setter

Imagine one bent round into a circle (like the internal structure of a
tyre). What would you get if it was made out of flexible materials at
the flat section at the bottom, where the thing spreads out?

I really can't think of any other way to make it any simpler for you?

Trouble is that it nothing like a real steel belt in a car tyre and is
encased in rubber too.

On Sat, 30 Jun 2018 03:41:41 +1000, "Jeff" wrote:

snip

Ok, please let us know when you come up with the answer. ;-)

Cheers, T i m

"dennis@home" wrote in message
...
On 29/06/2018 08:26, Tim Streater wrote:
In article , "dennis@home" wrote:

On 28/06/2018 21:19, Tim Streater wrote:
In article , "dennis@home" wrote:

On 28/06/2018 16:40, Tim Streater wrote:
In article , "dennis@home" wrote:

On 28/06/2018 10:59, The Natural Philosopher wrote:

What I wouuld ask you is how a tyre, rotating at a differentent
rate from a wheel, so that its circumference does in fact get
covered on the ground by that rotaion, stays on the wheel without
ripping the tread off?

This "philosopher" hasn't ever noticed the tyre debris on the roads
where the tread has been ripped off.

Maybe he wants to explain why it happens to lorries with twin wheels
where only one tyre has gone flat but is being kept at about the
correct radius by the other wheel?

Ah, nice attempt at a shimmy there, Den. Our Dave would be proud of
you.

What you're in fact admitting is that the wheel and the tire *must*
rotate at the same rate, otherwise the tread would come off.


How dumb can you be to think that is what I said?
I said the exact opposite of what you chose to claim I said.

Are you TNP ?

TNP says (above) that having a wheel rotating at a different rate to
the tire is only possible if the tread rips off.

You point out how much tire debris there is around.

QED.

You are just hoping nobody bothers to think about what you claim.

TNP says if they rotate at different rates the treads fall off..
I say treads do fall of.
You think it means I am agreeing with TNP.

You are.

Just think for a second instead of parroting TNP..
The tread changes length when it hits the road so that bit of the tyre
is rotating at a different rate to the rest so yes tyres do rotate at
different rates to the wheel some bits at one rate some at another and
some at all the values in between.

And over a revolution, the rate must be the same, else the tread would
come off.


You are being obtuse to troll.
The above says the rate varies around the tyre, the average is one rev of
the tyre is one rev of the wheel. The distance covered will be the
average.
The average will change depending on the static load, the pressure and the
dynamic load.
The reason it changes is because the circumference changes when all these
forces are acting on it.

Now snip that to try and prove I said something else but remember everyone
else has already read it except for the idiots like TNP that have
killfiled me because they can't argue with someone that is correct.

You shouldn't listen to TNP, he claims to understand engineering and
physics but as you can see from this thread he is closed minded and will
fight his position long after it has been shown to be wrong, just like
you.

You, TNP, and harry have that in common. I guess thats why you still
support brexit as you can't see the problems that it is producing and will
keep you "solutions" in your mind no matter how wrong they are proven to
be.

They just dont see that the alleged problems with BRexit are
important enough to cancel the decision to leave the EU and
that even if they were, the majority who bothered to vote said
that Britain should leave the EU and even May has decided that
thats what has to be done, regardless of any possible problems.

Yes, you can certainly make a case for another referendum
once the full detail of just what the EU will monster that
fool May and that other fool Davis into agreeing to but
IMO there is **** all chance that May will agree to that
and there isnt even much chance of that silly cow getting
the bums rush and another Tory remoaner getting the
job and allowing that either.

"Andy Burns" wrote in message
...
Jeff wrote:

Andy Burns wrote:
I can drop the pressure back to 31 and measure the drop of the axle

Yes please.

centre of wheel vertically to ground, 320mm vs 315mm

Interesting, and a lot smaller than I would have thought.

So now you have blown up the proof that it must be the
circumference that is changing, because that change is
less than the 0.4% you saw the ABS wheel rotation rate
change by. You bugger :-(

Jeff wrote:

you have blown up the proof that it must be the
circumference that is changing, because that change is
less than the 0.4% you saw the ABS wheel rotation rate
change by.

I make it a 1.5% change in "radius"

On 29/06/18 12:57, Thomas Prufer wrote:
On Fri, 29 Jun 2018 11:39:41 +0100, Andy Burns wrote:

Well, my axle is 5mm closer to the road (when stationary, who know how
much centrifugal [let's not have *that* discussion] force negates that
when moving?)

I'll inject facts into the handwaving fest:-)

A diagonally belted tire has 5% more travel per rotation at 180km/h than at
60km/h,

Is that what we would call a 'crossply'?

a radially belted tire 1% more.

Which is more than low/high pressure changes, so that's why they do
wheel to wheel comparisons..


This from the German Wiki page on the subject "Abrollumfang".

The article also contains the words "the dynamic rolling radius under load is
greater than the distance from the wheel middle to the road r sub(s)."

Which is in effect what I have been saying all along

and a
formula I can't be arsed to transcribe, but I'll toss in

r sub(0): unloaded wheel radius
r sub(s): static radius
r sub(D): dynamic radius

https://de.wikipedia.org/wiki/Abrollumfang


Thomas Prufer



--
"Nature does not give up the winter because people dislike the cold."

ۥ Confucius

On 29/06/18 19:16, Jeff wrote:


"Andy Burns" wrote in message
...
Jeff wrote:

Andy Burns wrote:
I can drop the pressure back to 31 and measure the drop of the axle

Yes please.

centre of wheel vertically to ground, 320mm vs 315mm

Interesting, and a lot smaller than I would have thought.

So now you have blown up the proof that it must be the
circumference that is changing, because that change is
less than the 0.4% you saw the ABS wheel rotation rate
change by. You bugger :-(

No, in fact he has proved it can't be the radius change because 5 mm
in 320mm is *more* than 0.4%. It's around 1.5%.

Ergo it has to be the circumference change due to elasticity

Denial is fascinating to watch


--
To ban Christmas, simply give turkeys the vote.

On 29/06/18 19:20, Andy Burns wrote:
Jeff wrote:

you have blown up the proof that it must be the
circumference that is changing, because that change is
less than the 0.4% you saw the ABS wheel rotation rate
change by.

I make it a 1.5% change in "radius"

Ah but you had an open mind to start with...


--
Microsoft : the best reason to go to Linux that ever existed.

The Natural Philosopher wrote:

Thomas Prufer wrote:

A diagonally belted tire

Is that what we would call aÂ* 'crossply'?

Just a normal radial ...

https://www.fastcar.co.uk/wp-content/uploads/2016/08/Fast-Car-Tyre-Guide-a.jpg

"dennis@home" wrote in message
...
On 29/06/2018 11:39, Andy Burns wrote:
Tim Streater wrote:

What I'm discounting is a *big* change
in circumference because the axle is "closer to the road"

Well, my axle is 5mm closer to the road (when stationary, who know how
much centrifugal [let's not have *that* discussion] force negates that
when moving?)

It negates it quite a lot..
I had a puncture and my front tyre went flat over a couple of hundred
yards in the roadworks on the M6. Rather than stop I continued to drive
for three miles to the end of the road works so I could get on the hard
shoulder.
When I got the tyre replaced there was no wear on the inside to show it
had been rubbing but the hole couldn't be fixed.
The car drove fine.
The only reason I knew it had gone was the TPMS (with pressure sensors)
told me.
I might have noticed if there had been a big bang and I had braked by
mistake.
Not that I recommend doing 50 mph on a flat tyre.


The other flat I had on the M6 was in the rear tyre when I ran over
something in the dark, that split the tyre and dented the rim.
After I pulled up on the hard shoulder there were about another 6 cars
pull up near me all with one or more flats.

I haven't had a flat since but there is always the chance.

There is no spare on the latest car nor anywhere to put one

Which car is that ? Stupid idea IMO.

so the AA can fix it next time.

Trouble with that approach is the annual cost of that and the much
longer time for them to show up than to change it yourself.

"dennis@home" wrote in message
...
On 29/06/2018 11:29, Andy Burns wrote:
The Natural Philosopher wrote:

Surprisingly low.

255/35R19 tyres, so not very "tall" to start with.

But greater than the % RPM change you measured isn't it?
1.5% instead of what you measured...0.4%.

Yep.


It might be but unless you can measure it under the dynamic conditions it
is just a guess.
I think it would be hard to get an accurate measurement while driving

Not really, shouldnt be hard to have a laser mounted
on an arm outside the car, from the roof rack

and a rolling road isn't going to help either.

Correct.

I don't suppose you have a laser you can exactly centre on the wheel and
suspend a measure down from the wheel arch with a slow mo camera to record
what actually happens? Not serious BTW.

It wouldnt be hard to do.

Jeff wrote:

Sounds like a relatively heavy vehicle given the 39 psi tyre pressure

Famous for their hard ride, Audi generally recommend high pressures, so
42F/39R for this one, which is a bit teeth-rattling over potholes.

I noticed Michelin for this car and tyres recommend 33F/29R which is a
big step down, I briefly tried them at those pressures this afternoon
and it felt like riding on balloons, so I'll try it on 38F/35R which is
a softer "Audi allowed" setting if you're not in autobahn mode.

On 29/06/2018 19:38, The Natural Philosopher wrote:
On 29/06/18 19:16, Jeff wrote:


"Andy Burns" wrote in message
...
Jeff wrote:

Andy Burns wrote:
I can drop the pressure back to 31 and measure the drop of the axle

Yes please.

centre of wheel vertically to ground, 320mm vs 315mm

Interesting, and a lot smaller than I would have thought.

So now you have blown up the proof that it must be the
circumference that is changing, because that change is
less than the 0.4% you saw the ABS wheel rotation rate
change by. You bugger :-(

No, in fact he has proved itÂ* can't be the radius changeÂ* because 5 mm
in 320mm is *more* than 0.4%. It's around 1.5%.

Ergo it has to be the circumference change due to elasticity

Denial is fascinating to watch



Watching TNP going from denying that the circumference changes and
quoting his engineering background as proof and now saying it does
change is fascinating. It makes you wonder how he expects anyone not to
notice.

On Fri, 29 Jun 2018 21:59:14 +0100, "dennis@home"
wrote:

snip

Watching TNP going from denying that the circumference changes and
quoting his engineering background as proof and now saying it does
change is fascinating.

He's one confused puppy that's for sure.

It makes you wonder how he expects anyone not to
notice.

I think they do, they just know what he's like and choose to ignore it
(basically because he can't help it).

I don't think most people would mind him just being a bit slow (he is
old after all) but it's all the 'attitude' that comes with it that
makes it more difficult to take him seriously. But hey, he told us
that is just his 'online persona' so I guess he knows what that's
going to ern him.

He's good to his few goblins though so that's something. ;-)

Cheers, T i m

"dennis@home" wrote in message
news
On 29/06/2018 19:38, The Natural Philosopher wrote:
On 29/06/18 19:16, Jeff wrote:


"Andy Burns" wrote in message
...
Jeff wrote:

Andy Burns wrote:
I can drop the pressure back to 31 and measure the drop of the axle

Yes please.

centre of wheel vertically to ground, 320mm vs 315mm

Interesting, and a lot smaller than I would have thought.

So now you have blown up the proof that it must be the
circumference that is changing, because that change is
less than the 0.4% you saw the ABS wheel rotation rate
change by. You bugger :-(

No, in fact he has proved it can't be the radius change because 5 mm in
320mm is *more* than 0.4%. It's around 1.5%.

Ergo it has to be the circumference change due to elasticity

Denial is fascinating to watch



Watching TNP going from denying that the circumference changes

He actually said originally that it changes by less than 1% and it turns
out that he was correct about that and it is now clear that the distance
between the axle and the road changes by much more than that, 3 times
more in fact, at least with that particular car and those tyre pressures.

and
quoting his engineering background as proof and now saying it does change
is fascinating. It makes you wonder how he expects anyone not to notice.

On 29/06/18 18:41, T i m wrote:
On Fri, 29 Jun 2018 13:57:07 +0200, Thomas Prufer
wrote:

On Fri, 29 Jun 2018 11:39:41 +0100, Andy Burns wrote:

Well, my axle is 5mm closer to the road (when stationary, who know how
much centrifugal [let's not have *that* discussion] force negates that
when moving?)

I'll inject facts into the handwaving fest:-)

I'm not sure it will make any difference Tomas as 'some people' don't
believe the facts, imperial evidence (millions of cars with iTPMS) and
the 'experts'.

empirical


They would prefer (if ever) to come to the exact same conclusion
themselves but shroud it very carefully in a desperate attempt to make
it look like they understood it all along and thinking they can hide
the *fact* they are indeed 'stupid and arrogant tw*ts'. ;-)

A diagonally belted tire has 5% more travel per rotation at 180km/h than at
60km/h, a radially belted tire 1% more.

So, that's because of the pantographing effect (like the dragster
drive wheel I linked to ages ago) as it is spun up, opposite to that
of a deflation (or course).

This from the German Wiki page on the subject "Abrollumfang".

The article also contains the words "the dynamic rolling radius under load is
greater than the distance from the wheel middle to the road r sub(s)." and a
formula I can't be arsed to transcribe, but I'll toss in

;-)

r sub(0): unloaded wheel radius
r sub(s): static radius
r sub(D): dynamic radius

The left brainers will 'get' the direct stuff but won't get the stuff
that requires some imagination.

https://de.wikipedia.org/wiki/Abrollumfang

Thanks for trying though. ;-)

Cheers, T i m

On 30/06/18 06:48, Richard wrote:
The left brainers will 'get' the direct stuff but won't get the stuff
that requires some imagination.

I see T i m is in complete denial and is in fact projecting everything
that he is and has done on this thread onto the people who were in fact
right all along.

Pore ole T i m.

Like Plowperson, he really needs medical trreament or therapy to help
with his mental condition.


--
The biggest threat to humanity comes from socialism, which has utterly
diverted our attention away from what really matters to our existential
survival, to indulging in navel gazing and faux moral investigations
into what the world ought to be, whilst we fail utterly to deal with
what it actually is.