Trailer Tires Overheating.
 

On Wed, 05 Nov 2003 06:25:44 GMT, (Steven Shelikoff)
wrote:

As a quick and dirty example, Nascar wheels are 15" dia x 9.5" wide.
The tires are 27.5" dia with a width of not more then 13.2". To make
things easier, assume flat sidewalls, which will make the area
calculation below come out on the low side. The sidewall area is around
2*(27.5-15)*pi = 78 sq in. Also ssume the wheel is a cylinder, which
will also make the area calculation come out on the low side so it sorta
cancels out. Also, assume that the bead takes up around 1/2" of the
wheel width on each side even though it's a little less, so the area
calculation of the wheel area will be a bit low. So the surface area of
the metal inside the tire is around 15*8.5*pi = 400 sq in, or about 5
times the sidewall area.

Holy cow, major brain fart. It's too late for deep thought.:) The area
of the sidewalls is 2*((13.75*13.75) - (7.5*7.5))*pi = 834 sq in. So
that's around twice the wheel surface area. However, those tires work
out to be a profile of around 50. Other types of racing, like F1, have
much lower profile tires so they have a much greater wheel area vs.
sidewall area.

In terms of profile, if you have a profile of 50 you'll have twice the
sidewall area as wheel area. A profile of 33 will give you about the
same sidewall area as wheel area inside the tire.

The funny thing is, that's the way I thought about it first but when the
math didn't work out, I didn't post it. The reason the math didn't work
out is that I was using the formula for circumference of a circle
instead of area of a circle to figure the sidewall area. Sheesh!

Steve

Trailer Tires Overheating.
 

Trailer Tires Overheating.
 

Steven Shelikoff wrote:

And I'm just saying that while in racing, the brake rotors themselves
can get extremely hot during braking, if there is so little heat taken
away that the rotors alone are causing the wheels to be heated up to
over 250 degrees then something's wrong with the setup.

Once again, I never said car or trailer tires were heated by the brakes.

Holy cow, major brain fart.

Understand that very well ...

I don't buy the "runs cooler" argument either. But I do buy
the argument that you can control the amount of moisture in
the gas easier if you're filling it with nitrogen then when
plain compressed air.

Yes, yes, that's it! Finally! 8-) That is what has been so difficult to
get across here ... that control of moisture in the filling gas - along
with the oxidation reducing benefits of an inert gas - is the the sole
reason to choose nitrogen over home brew compressed air.

Dry nitrogen can not make a tire run cooler and it does not expand at a
different rate than dry air. Water will not flash to steam below its
vapor pressure.

Rick

Trailer Tires Overheating.
 

"basskisser" wrote in message
om...

Pure horse****!!!!! They do, indeed, keep the throttle wide open, but
they DO use the brakes, and quite a lot. They use the brakes as
opposed to letting up on the throttle when drafting, to avoid loosing
engine rpms from what is commonly refered to as "lifting".


I ask you again: What type of connection do they use between the engine and
the wheels that allows the engine RPMs to stay high while the car slows
down?

Rod

Trailer Tires Overheating.
 

"Mark Browne" wrote in message
news:Q_Zpb.109411$Fm2.94923@attbi_s04...



Conventional wisdom is
that the measured pressure increase is due to liquid water flashing to
steam
above the boiling point of water.

There are a few simple things you could do to eliminate the liquid water in
the tires:

1) Install a water separator on the air line between the compressor and your
inflation nozzel. Standard equipment on most air systems.

2) Don't mount the tires outside in a driving rain!

In the turns NASCAR and F1 cars run peak
tire temperatures between 225 and 250 degrees F. I leave it to you to
offer
an alternate explanation of the measured 4 to 16 PSI jump (nominal 30 PSI)
under racing conditions.

Are you saying that as the tire temperature changes from 225 and 250
degrees F (685 to 710 degrees R) the tire pressure changes from 30psig to
46psig ( 44.7 psi to 60.7psi at sea level) ??

pv/t = PV/T . IF the volume stays constant (not a good assumption) so
44.7V/685 should equal 60.7V/710
0.065 does not equal 0.085. Nope, something else going on here.

Hmmm, sure doesn't follow the steam tables. According to the steam tables
publised by the American Society of Mechanical Engineers (the accepted
standard) the internal temperature would have to be up to around 294 degrees
F to have boiling water create that kind of pressure. Nope, isn't steam.

And you say this doesn't happen when you use Nitrogen?

You said that this happens in the turns, so I can explain why you would get
a sharp increase, but I can't explain why you didn't see the same increase
using nitrogen. In the turns, the tire is going to be subjected to a
significant amount of lateral force. This force is going to distort the
shape of the tire, hence its volume will decrease. As you decrease the
volume, the pressure will increase. You are changing a second variable in
the PV/T equation.


This stuff is not conjecture - it is measured data. If it does not match
your expectations - perhaps it is time to reexamine your expectations.

What other gases did you try this with? Did you try dry air? Did you try
carbon dioxide?
The water theory would have been trival to eliminate by simply eliminating
the water, did you do that?
Did you try adding a little water to nitrogen and seeing if it behaved just
like air?

Numbers are wimps, if you torture them enough they will confess to anything.
To throw out the ideal gas laws because your measurements didn't agree, and
then say "Conventional wisdom is that the measured pressure increase is due
to liquid water flashing to steam" is absolutly conjecture.

Maybe there is something else going on. Too bad you didn't follow the
scientific method properly and try to figure out what it was. Change one
variable at a time and you have a much better chance of establishing what
the cause and effect relationships are.

Nitrogen is a funny gas. At sea level pressures and room temperatures it is
generally inert and safe to use for many applications. If you increase the
pressure, that is no longer true. SCUBA divers all know that under a few
additional atmosphers of pressure Nitrogen does BAD things to the human
body. Oxyen is even worse, double the pressure of oxygen and it suddenly
becomes toxic in its pure state. Perhaps what is really going on is that at
those pressures and temperatures the oxygen in the air is reacting with the
rubber compound of the tires, makng them more pliable.

Rod

Trailer Tires Overheating.
 

On 5 Nov 2003 04:41:14 -0800, (basskisser) wrote:

(Steven Shelikoff) wrote in message ...
On 3 Nov 2003 05:02:04 -0800, (basskisser) wrote:

Steven Shelikoff, the racing expert wrote:


Actually, the area of the wheel exposed to the gas in a race car tire is
pretty large compared to the area of the tire since they are wide and
low profile.

Not in all types of racing. Actually, in some types, the narrower the
better, less contact area, less friction. Take a salt flat racer, for
instance.

Yeah, and bicycle racing.

Though it doesn't apply much to boat trailer tires, the heat
conductivity of the gas would work against tire cooling in the case of
race cars and aircraft since it would serve to increase the rate of tire
heating in heavy brake application. Many aircraft tire failures are due

Of course it all depends on the type of racing. During most racing like
road racing, twisty corners, etc, heavy braking is applied but for very
short durations. Superspeedway racing, not at all.

Are you really trying to say that on superspeedways, they don't use
brakes at all? That's pretty stupid. They actually use brakes as
opposed to letting off the throttle, trying to keep the enginer RPM's
up. It takes forever to get those restictor plate engines back up to
speed. They do, however, use completely different brake setups,
smaller rotors, pads. These smaller, thinner rotors will get quite
hot, quite quickly.

Sorry to dissapoint you but at NASCAR restrictor plate races like at
Talladega and Daytona, the driver will almost without exception have
the gas pedal to the floor and not touch the brakes all day.

Pure horse****!!!!! They do, indeed, keep the throttle wide open, but
they DO use the brakes, and quite a lot. They use the brakes as
opposed to letting up on the throttle when drafting, to avoid loosing
engine rpms from what is commonly refered to as "lifting". So, to say
that they "not touch the brakes all day" is, again, false.

As usual, you need to do a little more research. But as usual, even
when you learn that you're wrong, you won't believe it and try to put
some sort of spin on it to avoid admitting you don't know what the hell
you're talking about.

They even
tape up the brake vents for more downforce since there's little need to
cool the brakes.

Actually, almost all teams don't even use brake ducting on
superspeedways, if that is what you mean by "brake vents".

They don't use brake ducting because they don't use he brakes. If they
used the brakes "quite a lot" as you claim, without any ducting, then
Rick would be right in that the brakes would melt the tires.

That's the exact opposite from short track and road course races where
they use the brakes so much that they need blowers to cool the them
since the vents don't provide enough cooling. They use a beefy braking
setup for those races since they have twice the power available so
there's much more to overcome braking losses, and they really need the
brakes.

The "beefy" brakes are because they have to slow the car from say,
130mph in the straight at Bristol, down to 60mph in turns 1 and 2, in
the shortest amount of time. It's all about being able to hold that
130mph until the last possible moment, slamming on the brakes until
the car takes a "set" (meaning it goes from pushing, or understeer, to
loose, or oversteer.), then being able to get back into the throttle.
Of course, I'm sure, you are an expert, as always!!!!
Oh, and your Nascar tire diatribe is wrong, and stupid.

You're too funny. Are you sure you're not Jax?

Steve

Trailer Tires Overheating.
 

On Wed, 5 Nov 2003 11:11:13 -0800, "Rod McInnis"
wrote:


"basskisser" wrote in message
. com...

Pure horse****!!!!! They do, indeed, keep the throttle wide open, but
they DO use the brakes, and quite a lot. They use the brakes as
opposed to letting up on the throttle when drafting, to avoid loosing
engine rpms from what is commonly refered to as "lifting".


I ask you again: What type of connection do they use between the engine and
the wheels that allows the engine RPMs to stay high while the car slows
down?

He's full of crap as usual. They do use the brakes without lifting off
the gas pedal but not to avoid loosing engine rpms. It avoids the short
time lag in getting power back if you lift off the pedal. It also
avoids abrupt changes in handling and suspension geometry that you get
when you lift off the gas pedal, which shifts the front/rear weight
distribution around.

Steve

Trailer Tires Overheating.
 

Trailer Tires Overheating.
 

"Rod McInnis" wrote in message ...
"basskisser" wrote in message
om...

Pure horse****!!!!! They do, indeed, keep the throttle wide open, but
they DO use the brakes, and quite a lot. They use the brakes as
opposed to letting up on the throttle when drafting, to avoid loosing
engine rpms from what is commonly refered to as "lifting".


I ask you again: What type of connection do they use between the engine and
the wheels that allows the engine RPMs to stay high while the car slows
down?

Rod

It doesn't. What happens is that by not lifting the throttle, you are
keeping the same amount of fuel/air ramming into the engine. So, what
happens is that when you quit braking, the RPM's come back up quicker.
You see, if you don't do that, with the restrictor plates, it can take
up to a lap to get back up to full speed. So, when I say it is to
avoid loosing RPM's, it really means loosing RPM's for a full lap, as
opposed to a few seconds. It is a VERY common practice on
superspeedways, and they all do it. It's just that Shelikoff doesn't
know that.

Trailer Tires Overheating.
 

On 6 Nov 2003 04:55:09 -0800, (basskisser) wrote:

"Rod McInnis" wrote in message ...
"basskisser" wrote in message
om...

Pure horse****!!!!! They do, indeed, keep the throttle wide open, but
they DO use the brakes, and quite a lot. They use the brakes as
opposed to letting up on the throttle when drafting, to avoid loosing
engine rpms from what is commonly refered to as "lifting".


I ask you again: What type of connection do they use between the engine and
the wheels that allows the engine RPMs to stay high while the car slows
down?

Rod

It doesn't. What happens is that by not lifting the throttle, you are
keeping the same amount of fuel/air ramming into the engine. So, what
happens is that when you quit braking, the RPM's come back up quicker.
You see, if you don't do that, with the restrictor plates, it can take
up to a lap to get back up to full speed. So, when I say it is to
avoid loosing RPM's, it really means loosing RPM's for a full lap, as
opposed to a few seconds. It is a VERY common practice on
superspeedways, and they all do it. It's just that Shelikoff doesn't
know that.

lol... rpm's come back quicker. Loosing rpm's for a full lap... You
have no idea what you're talking about. Let me give you a hint: if a
driver brakes in the middle of racing during a restrictor plate race,
he's gonna loose a whole lot of positions. And they are tough to get
back.

Steve