RCR rims, NASACAR SAYS IT DIDN'T HAPPEN

#31

"SimRacer" <nOspaM@simracer68 (AT) yahoo (DOT) com> wrote

Quote:

I think you clarified just what I was trying to say there Carey. I
admitted
to not being a rocket scientist because I know basically what I was trying
to say, even if it didn't come out exactly correct. I know they use
nitrogen
for its relative stablility, inertness (if that's a word) and its
availability. Nitrogen is also what drives the impact wrenches that the
tire
changers use on pit road.

Again, because of its characteristics and cost.

Quote:

That's what was getting me. A slot or hole, without some sort of
pressure-actuated cutoff valve, is a effectively a HOLE in the dang tire.
Pressure build up or no, the "air" would literally bleed out until the
tire
was flat. There has to be a cutoff "device" somewhere in this equation for
the whole thing to work. Likely something in the 50-60psi range, depending
on the car's setup. Maybe lower, I am not that familiar with the current
GY
compounds. Back in the "older" days of the late 90s and early 2000s, about
60 PSI cold was the max tire pressure recommend by GY - and they only went
that high at the plate tracks to decrease the tires' rolling resistence.

Yup. A tire bead isn't going to lead and then re-seal. I thought that the

air pressures were much lower than that. I don't know what you run on your
race car, but our full size car usually ranges between 8-15 psi, depending
on track, car location, etc. I do know that the pressure for asphalt would
be higher. Hell, on a sprint car, you don't even want to know how low those
pressures get. And that is where bleeders come in to play.

Carey in Manvel

#32

"SimRacer" <nOspaM@simracer68 (AT) yahoo (DOT) com> wrote

Quote:

AMEN! Preach on Carey. The tires, outside of providing the contact patch,
are also an extension of the suspension. Their "air pressure" affects the
spring rate of the specific corner to which they are attached. There are
other variables, of course, like sidewall firmness, and what have you, but
my basic premise, is correct IMO.

And if you want to get REAL technical (and Carey you can confirm, deny, or
fine tune this), each corner of the car also affects the opposite corner
when talking about suspension and crossweight settings. IE: What you do to
the suspension and/or "tire pressure" on the RR (including track bar and
wedge settings), has a direct affect on the LF. And vice versa and so on
and
so forth. I wish I had a nice 4-way scale illustration to show this, as it
is amazing to the uninitiated the first time they see a change to the RR
affect the weight on the LF (again, just as an example).

Absolutely. We look at crossweight all the time. And that isn't "real"

technical.

Carey in Manvel

#33

"Carey Akin" <cmakin (AT) att (DOT) net> wrote

Quote:

"SimRacer" <nOspaM@simracer68 (AT) yahoo (DOT) com> wrote in message
news

gXPg.31524$Md4.13981 (AT) tornado (DOT) southeast.rr.com...

I think you clarified just what I was trying to say there Carey. I
admitted
to not being a rocket scientist because I know basically what I was
trying
to say, even if it didn't come out exactly correct. I know they use
nitrogen
for its relative stablility, inertness (if that's a word) and its
availability. Nitrogen is also what drives the impact wrenches that the
tire
changers use on pit road.

Again, because of its characteristics and cost.

That's what was getting me. A slot or hole, without some sort of
pressure-actuated cutoff valve, is a effectively a HOLE in the dang
tire.
Pressure build up or no, the "air" would literally bleed out until the
tire
was flat. There has to be a cutoff "device" somewhere in this equation
for
the whole thing to work. Likely something in the 50-60psi range,
depending
on the car's setup. Maybe lower, I am not that familiar with the current
GY
compounds. Back in the "older" days of the late 90s and early 2000s,
about
60 PSI cold was the max tire pressure recommend by GY - and they only
went
that high at the plate tracks to decrease the tires' rolling resistence.

Yup. A tire bead isn't going to lead and then re-seal. I thought that
the
air pressures were much lower than that.

I am sure they are, usually down in the low 20s on asphalt, in NASCAR-type
cars (with older compunds anyway). I was just stating the old max, since
they used to actually discuss this on various shows, and as it happened, for
about 5-6 years, it carried directly over to our racing sim. We did go max
on the plate tracks, and for everything else, we'd do a run, examine the
heat across the tire, develop the average we wanted across those 3 temps (I,
M, O) and adjust our starting pressures as needed to attain that average as
the temps crested in the run. In the old days, our target cross-tire average
temp in the sim (and in real life according to the CCs on the tube) was
around 220º

Just note sometime when they discuss it on TV, that GY often will set a
minimum PSI setting to prevent tire problems early in a run, so you KNOW
they're pushing the limits at times trying to keep the buildup down, by
starting WAY low.

Quote:

I don't know what you run on your
race car, but our full size car usually ranges between 8-15 psi, depending
on track, car location, etc.

I run on asphalt, and our runs aren't *that* long. We generally start at
around 18 pounds on average, sometimes around 15 psi if the surface is rough
and fast. Obviously, it various from car side to car side depending on
surface and banking. Very seldom will our hot PSI at the end of a run exceed
35 lbs and is usually in the high 20s. BUT, we use "air" and nothing so
fancy as nitrogen. And our impact wrenches, are cordless battery
powered...lol

Quote:

I do know that the pressure for asphalt would
be higher. Hell, on a sprint car, you don't even want to know how low
those
pressures get. And that is where bleeders come in to play.

Oh yeah, those sprint tires look absolutely flat on TV sometimes. I imagine
their cold/starting PSI is in the single digits. Much like the wrinkle-wall
tires that the NHRA uses. Those have some scary low PSI numbers at times if
I had to guess too.

Quote:

Carey in Manvel

#34

"Gordon" <jimmygator (AT) gmail (DOT) com> wrote

Quote:

I thought the issue with nitrogen was it would be less susceptable to heat
build up than would a mix of 21%~ oxygen and 79%~ nitrogen resulting in
less difference in pressure from
a cold tire to a hot tire?

Go see what I wrote about the difference.

Carey in Manvel

#35

"Carey Akin" <cmakin (AT) att (DOT) net> wrote

Quote:

"SimRacer" <nOspaM@simracer68 (AT) yahoo (DOT) com> wrote in message
news:T6YPg.31532$Md4.788 (AT) tornado (DOT) southeast.rr.com...

AMEN! Preach on Carey. The tires, outside of providing the contact
patch,
are also an extension of the suspension. Their "air pressure" affects
the
spring rate of the specific corner to which they are attached. There are
other variables, of course, like sidewall firmness, and what have you,
but
my basic premise, is correct IMO.

And if you want to get REAL technical (and Carey you can confirm, deny,
or
fine tune this), each corner of the car also affects the opposite corner
when talking about suspension and crossweight settings. IE: What you do
to
the suspension and/or "tire pressure" on the RR (including track bar and
wedge settings), has a direct affect on the LF. And vice versa and so on
and
so forth. I wish I had a nice 4-way scale illustration to show this, as
it
is amazing to the uninitiated the first time they see a change to the RR
affect the weight on the LF (again, just as an example).

Absolutely. We look at crossweight all the time. And that isn't "real"
technical.

Carey in Manvel

Well, it can be to some. Consider that the TV people say "They're going up
(or down) on the X tire pressure", but never cover if they made a
counter-adjustment to the other corner or that it even affects the other
corner - which it does.

I know when I was simming in Cup cars, in regards to adjustments made during
pit stops, I often had to offset a track bar adjustment with a LF tire
pressure adjustment to keep the temps from ramping up (or not getting hot
enough) at that corner after putting more or less weight on it. Higher temps
meant more buildup, more buildup meant stiffer spring rate, spring rate
affects cornering (at least turn in, if not all the way around)....it was a
viscous cycle that made me glad I was not a CC.

With my current little hobby car, we don't pit, so we've "got what we got"
once we leave the pits and all this is moot once the race starts. We have to
guess at it before the race and analyze the results post-race in my class -
and try to learn, and certainly keep a notebook...

#36

"SimRacer" <nOspaM@simracer68 (AT) yahoo (DOT) com> wrote

Quote:

Well, it can be to some. Consider that the TV people say "They're going up
(or down) on the X tire pressure", but never cover if they made a
counter-adjustment to the other corner or that it even affects the other
corner - which it does.

I know when I was simming in Cup cars, in regards to adjustments made
during
pit stops, I often had to offset a track bar adjustment with a LF tire
pressure adjustment to keep the temps from ramping up (or not getting hot
enough) at that corner after putting more or less weight on it. Higher
temps
meant more buildup, more buildup meant stiffer spring rate, spring rate
affects cornering (at least turn in, if not all the way around)....it was
a
viscous cycle that made me glad I was not a CC.

With my current little hobby car, we don't pit, so we've "got what we got"
once we leave the pits and all this is moot once the race starts. We have
to
guess at it before the race and analyze the results post-race in my
class -
and try to learn, and certainly keep a notebook...

We scale the car before it gets put on the trailer before we leave for the

track. At the track, we guess on the track conditions and consult the book.
Before we leave, we have the set up on the car that we think will work.
What adds our difference is that for a track bar we use adjustable "j-bars".
We will also pre-load the chassis depending on how we want the car. As
things change through the night, so do our tire pressures, wedge settings,
j-bars and j-bar positions, etc. We will also adjust our tires depending on
needed roll out. At least most folks in our division don't have huge pocket
books, so we don't have to worry about a whole lot of tires with different
compounds. And it all goes in the notebook. As soon as the car gets off
the track ,we are measuring tire temperature and pressure and listening to
what our driver has to say about how the car handled and where.

Carey in Manvel

#37

"SimRacer" <nOspaM@simracer68 (AT) yahoo (DOT) com> wrote

Quote:

snip
I run on asphalt, and our runs aren't *that* long. We generally start at
around 18 pounds on average, sometimes around 15 psi if the surface is
rough
and fast. Obviously, it various from car side to car side depending on
surface and banking. Very seldom will our hot PSI at the end of a run
exceed
35 lbs and is usually in the high 20s. BUT, we use "air" and nothing so
fancy as nitrogen. And our impact wrenches, are cordless battery
powered...lol

The last team I ran with used nitrogen, just because the car owner had an
unlimited supply. Some teams use it, some don't. It isn't that expensive.
Oh, we have the electric impact, too.

Quote:

Oh yeah, those sprint tires look absolutely flat on TV sometimes. I
imagine
their cold/starting PSI is in the single digits. Much like the
wrinkle-wall
tires that the NHRA uses. Those have some scary low PSI numbers at times
if
I had to guess too.

4psi on a dry track isn't unusual. It IS a pain in the ass when a bleeder

gets stuck open with a piece of dirt or other trash, though.

Carey in Manvel

#38

"SimRacer" <nOspaM@simracer68 (AT) yahoo (DOT) com> wrote

Quote:

"Michael E" <racingfast (AT) anycost (DOT) org> wrote in message
news:Z_ydneESaOqF0o3YnZ2dnUVZ_rednZ2d (AT) comcast (DOT) com...

"SimRacer"<nOspaM@simracer68 (AT) yahoo (DOT) com> wrote

Right on Carey. I didn't think I could make it any plainer. Guess I
have
to
remember the audience on occasion...

I've often wondered why it is that you only seem to communicate with a
small
portion of those who use this forum.
Your last statement tells me all that I need to know about that
situation.

Hey, it's a free country. I'll consider myself KF'd on your end, and we
should be fine then.

I don't use killfiles for anyone other than political crossposters or

habitual trolls. I just choose to ignore the assholes, thank you.

#39

"SimRacer" <nOspaM@simracer68 (AT) yahoo (DOT) com> wrote

Quote:

I was just correcting his statement/reading of my statement. I don't know
that nitrogen builds up any more or less. And I don't think pure O2 in a
racing tire is *that big* of a fire hazard - but when compressed and in an
environment totally encapsulated in O2, it can be very flammable. It was
the
reason that the Apollo 1 fire was as instant and as deadly to the
astronauts
(Grissom, Chaffey & White?) as it was, the capsule was sealed and totally
O2
filled. One small spark/flare up killed those 3 guys in a matter of
seconds.
I think it's also the reason you can't smoke in hospital rooms.

Oxygen itself does not burn, but is necessary for combustion. The right mix
of fuel (oil), oxygen and pressure (heat) will ignite. From my firefighting
days, I remember the fire triangle. Fuel, heat and oxygen. Take away any
one item and the fire will be gone. Needless to say, in Apollo 1, there
were many things that acted as fuel. They had the right temperature and
mixture of oxygen and fuel.

Quote:

Regardless, the buildup in pressure in the current tires is usually pretty
good. I dunno if it would be anymore with "air" (a mix of gases beyond O2
as
Carey has indicated) than it is with nitrogen or not. I just assume it
would
simply be less predictable (using "air") from tire to tire, from tire set
to
tire set, and is the reason they use a more pure and inert gas, to try
and
eliminate some of the guess work in just how much the clearinghouse of
gases/vapors that comprise "air" would be. I'm sure if you sampled the air
right beside you at any given time you'd find O2, H2O, CO, CO2, methane,
nitrogen, and so on.

You are correct. Of course water vapor has its own issues (condensation and

the related issues with that). The expansion is a factor of the
compound/element and goes to the physics/chemical make up. If I recall
those old classes right, it depends on the molar equivalent. As you stated,
however, the best reason is the predictability and consistency. Especially
from track to track, location to location. To best determine how your car
will perform is a matter of controlling all the variable that you can.
There aren't a whole lot out there, but by using nitrogen in the tires, that
is one item that will not change, no matter what (unless you get a doctored
batch, I guess).

Carey in Manvel

#40

"Carey Akin" <cmakin (AT) att (DOT) net> wrote

Quote:

"SimRacer" <nOspaM@simracer68 (AT) yahoo (DOT) com> wrote in message
news:YHYPg.31537$Md4.27496 (AT) tornado (DOT) southeast.rr.com...

snip
I run on asphalt, and our runs aren't *that* long. We generally start at
around 18 pounds on average, sometimes around 15 psi if the surface is
rough
and fast. Obviously, it various from car side to car side depending on
surface and banking. Very seldom will our hot PSI at the end of a run
exceed
35 lbs and is usually in the high 20s. BUT, we use "air" and nothing so
fancy as nitrogen. And our impact wrenches, are cordless battery
powered...lol

The last team I ran with used nitrogen, just because the car owner had an
unlimited supply. Some teams use it, some don't. It isn't that
expensive.
Oh, we have the electric impact, too.

If I was into more than just casually, and ran a class that actually held
more races and paid more money, I'd probably go with nitrogen too. Not for
the cost, really, but for the issue of finding it and keeping it on hand. As
it is, it's a basic single stage 10 gallon Craftsman air compressor that I
run off my generator (if I need more air than we pack into the track). That
also comes in handy when I need the strength of an air ratchet or some other
basic air-powered power tool.

Quote:

Oh yeah, those sprint tires look absolutely flat on TV sometimes. I
imagine
their cold/starting PSI is in the single digits. Much like the
wrinkle-wall
tires that the NHRA uses. Those have some scary low PSI numbers at times
if
I had to guess too.

4psi on a dry track isn't unusual. It IS a pain in the ass when a bleeder
gets stuck open with a piece of dirt or other trash, though.

Yeah, I was thinking 5-8 psi, so 4 psi doesn't shock me. Plus I grasp the
conceptual difference between PSI and volume. A big tire can have plenty of
"air" in it, but that air be at a low PSI, and all work great. Then you have
a racing bicycle tire can have very little volume, but be spec'd for close
to 110 psi....sounds crazy on the surface, but makes all sorts of sense on
the scientific level.

Quote:

Carey in Manvel