rec.autos.simulators

NR2002 tire circumference

Larr

NR2002 tire circumference

by Larr » Fri, 11 Oct 2002 12:16:07

What Tire Pressure?

-Larry


Larr

NR2002 tire circumference

by Larr » Fri, 11 Oct 2002 12:16:57

Oh, shit.  Someone done broke out the slide rule.  Check please!

:)

-Larry





> Uhm, radius or circumference? I'd say circumference stays quite the
> same in all cases, unless you calculate it as 2*PI*r. ;-)

> Ruud van Gaal
> Free car sim: http://www.racer.nl/
> Pencil art  : http://www.marketgraph.nl/gallery/

Ruud van Ga

NR2002 tire circumference

by Ruud van Ga » Fri, 11 Oct 2002 21:08:50




>> Uhm, radius or circumference? I'd say circumference stays quite the
>> same in all cases, unless you calculate it as 2*PI*r. ;-)

>Ah, but having given it some thought, one could assume that it's the
>"roll radius" which is important here and that changes with the pressure
>in the tire ?

Right, it's called Re; effective radius at load X.
However, there's a world of information behind this, since the radius
from the axis down is different from the radius going up to the top of
the wheel. So there is no one radius.
So Re is really just an average which is more of an empirical result;
if after 1km your wheels have rotated X times, then (assuming no tire
slip) the effective circumference can be calculated as 1km/X (did I
miss a factor here?). From which you can calculate Re. Not nice in
sims, but there has been work done on this, to estimate Re using Yet
Another Set of Pacejka Coefficients (tm).

I just use the wheel radius all the time. :) I think the radius change
is a secondary effect with respect to tire temp changes.

Quite good. ;-)

Ruud van Gaal
Free car sim: http://www.racer.nl/
Pencil art  : http://www.marketgraph.nl/gallery/

Ruud van Ga

NR2002 tire circumference

by Ruud van Ga » Fri, 11 Oct 2002 21:09:49


>What Tire Pressure?

Good Year *** or Bridgestone ***? :)

>-Larry



>> Anybody know?

Ruud van Gaal
Free car sim: http://www.racesimcentral.net/
Pencil art  : http://www.racesimcentral.net/
Goy Larse

NR2002 tire circumference

by Goy Larse » Fri, 11 Oct 2002 22:50:49





> >> Uhm, radius or circumference? I'd say circumference stays quite the
> >> same in all cases, unless you calculate it as 2*PI*r. ;-)

> >Ah, but having given it some thought, one could assume that it's the
> >"roll radius" which is important here and that changes with the pressure
> >in the tire ?

> Right, it's called Re; effective radius at load X.
> However, there's a world of information behind this, since the radius
> from the axis down is different from the radius going up to the top of
> the wheel. So there is no one radius.
> So Re is really just an average which is more of an empirical result;
> if after 1km your wheels have rotated X times, then (assuming no tire
> slip) the effective circumference can be calculated as 1km/X (did I
> miss a factor here?). From which you can calculate Re. Not nice in
> sims, but there has been work done on this, to estimate Re using Yet
> Another Set of Pacejka Coefficients (tm).

> I just use the wheel radius all the time. :) I think the radius change
> is a secondary effect with respect to tire temp changes.

Couldn't have said it better myself......:-)

Why thank you

Beers and cheers
(uncle) Goy

"The Pits"    http://www.theuspits.com/

"A man is only as old as the woman he feels"
--Groucho Marx--

Tom Osbo

NR2002 tire circumference

by Tom Osbo » Sat, 12 Oct 2002 00:49:03

With inner liner or without




> >What Tire Pressure?

> Good Year *** or Bridgestone ***? :)

> >-Larry



> >> Anybody know?

> Ruud van Gaal
> Free car sim: http://www.racesimcentral.net/
> Pencil art  : http://www.racesimcentral.net/

Gerald Moo

NR2002 tire circumference

by Gerald Moo » Sat, 12 Oct 2002 02:13:53


> What Tire Pressure?

> -Larry



> > Anybody know?

Let's say it's roughly equal to all the hot air that has been let out
thus far in response to (what I thought (that's my problem, btw)
should be) a simple question!  ;)  LOL, j/k, etc...

How 'bout a ballpark figure, "under normal driving conditions", LOL.

I am looking for something so I can "guestimate" what gear ratio I
need for a given speed at a given rpm, without having to do a lot of
trial and error.

Wouldn't circumference always be (practically) the same, anyway?

Gerald

Tom Osbo

NR2002 tire circumference

by Tom Osbo » Sat, 12 Oct 2002 09:26:15

28.5 inches



> > What Tire Pressure?

> > -Larry



> > > Anybody know?

> Let's say it's roughly equal to all the hot air that has been let out
> thus far in response to (what I thought (that's my problem, btw)
> should be) a simple question!  ;)  LOL, j/k, etc...

> How 'bout a ballpark figure, "under normal driving conditions", LOL.

> I am looking for something so I can "guestimate" what gear ratio I
> need for a given speed at a given rpm, without having to do a lot of
> trial and error.

> Wouldn't circumference always be (practically) the same, anyway?

> Gerald

Ruud van Ga

NR2002 tire circumference

by Ruud van Ga » Sat, 12 Oct 2002 18:57:00


>28.5 inches

And circumference is practically the same yes. When spinning, the tire
wants to bulge anyway, so even if the loaded radius is a little less,
the circumference (distance per tire rotation) is just about the same.

Take care of the 'final drive ratio'; the diff ratio. That's part of
the gearing too.

Ruud





>> > What Tire Pressure?

>> > -Larry



>> > > Anybody know?

>> Let's say it's roughly equal to all the hot air that has been let out
>> thus far in response to (what I thought (that's my problem, btw)
>> should be) a simple question!  ;)  LOL, j/k, etc...

>> How 'bout a ballpark figure, "under normal driving conditions", LOL.

>> I am looking for something so I can "guestimate" what gear ratio I
>> need for a given speed at a given rpm, without having to do a lot of
>> trial and error.

>> Wouldn't circumference always be (practically) the same, anyway?

>> Gerald

Ruud van Gaal
Free car sim: http://www.racer.nl/
Pencil art  : http://www.marketgraph.nl/gallery/
Gerald Moo

NR2002 tire circumference

by Gerald Moo » Sat, 12 Oct 2002 22:05:01

That's diameter, I'm sure, but thanks.  I saw somebody quote the
rulebook that it was 27.5" but I'm sure it is really whatever tire
goodyear happens to bring to race weekend, prolly a bit of a range.

I haven't had a chance to test out whether or not the game varies the
size based on pressure or not.  Wish the tach was a bit more
precise/readible.

Gerald


> 28.5 inches





> > > What Tire Pressure?

> > > -Larry



> > > > Anybody know?

> > Let's say it's roughly equal to all the hot air that has been let out
> > thus far in response to (what I thought (that's my problem, btw)
> > should be) a simple question!  ;)  LOL, j/k, etc...

> > How 'bout a ballpark figure, "under normal driving conditions", LOL.

> > I am looking for something so I can "guestimate" what gear ratio I
> > need for a given speed at a given rpm, without having to do a lot of
> > trial and error.

> > Wouldn't circumference always be (practically) the same, anyway?

> > Gerald


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