Speed Demon Wind Tunnel Test

[Stainless1]

We have also used Nitrogen in our tires for years... easier to take a small "walk around" bottle than than a compressor. 
John C, the problem with tires for some folks is a heavy right foot... luckily for us we use small enough motors that spinning the tires is about impossible.   
Something to consider, traction on salt is about 60% of cement 
Tire slip is one of the enemies...

[Interested Observer]

The reason that nitrogen can have an effect on tire pressure is that the way nitrogen is refined out of the air. It has an extremely low due point i.e. very low water content. Heat in tires is generated by tire flex and slip, if you have any water in the tire it will expand at a faster rate than a normal gas because it is turning to steam. A dry gas expands proportional to its change in temperature (in degrees kelvin ). When water changes to steam at 212F it expands at a ratio of 1700:1. You can get the same affect by using air that has been compressed and then dried using a desiccant dryer which typically reduces the due point to -40 degrees F, a refrigerant air dryer reduces the due point to 32 degree F at best. So you can certainly use compressed air for your tires but the compressor needs to have a desiccant dryer, or just use nitrogen.

Rex




While much of what Rex stated is valid, things kind of went off the rails when talking about boiling water in the tires.  While some vehicles (like tractors) have liquid water in the tires, it is not likely any LSR competitors do, nor do they likely get up to boiling temperatures.
Perhaps to clarify the issue of using Nitrogen in the tires it would be useful to consider the following.  From thermodynamics and the related gas laws, it is possible to derive the following relationship for a mixture of gasses, namely air and water vapor.

   V = (1 + xRw/Ra) Ra T/p
Where
   V = volume
   T = temperature
   p = pressure
   Ra = gas constant for air
   Rw = gas constant for water vapor
   and Rw/Ra = 1.61
   x = specific humidity = mw/ma = ratio of the mass of water vapor to the mass of air

So looking at the formula, if there is dry air alone, that is, x = 0, the relationship simplifies to the more commonly familiar V = RT/p.   Which says that for volume to remain constant (assuming the interior volume of an inflated tire is essentially constant), if the temperature were to rise, the pressure would also have to rise in proportion, to keep V = constant.  Pressure goes up in a hotter tire.
If we then consider water vapor to be in the mixture, x will be greater than zero and since Rw/Ra = 1.61, the value in the parentheses will be greater than 1 and consequently, given a temperature increase, p will have to increase at a greater rate than before in order to comply with a constant volume requirement.  Ergo, air with water vapor will produce a larger pressure increase.
So, if the nitrogen gas is ?dry? it would not produce as much pressure rise as possibly water vapor  contaminated gas would, and since the gas constant for nitrogen Rn is slightly less than that of air, another minor effect would be acting to minimize the pressure rise.

However, all of these effects are relatively small and of dubious value for LSR competition.

[Stan Back]

I think it's "dew" (like dew on the leafs) rather than "due" (like your library book).

[floydjer]

Who the heck fills tractor tires with water??....Beet juice is the way to go.

[John Clutch]

I think it's "dew" (like dew on the leafs) rather than "due" (like your library book).

I would like to demote our forum spell checker until he corrects his own name to Stand.

Thanks.

[floydjer]

Wait until Jim corrects your grammar...and your grandpa too.

[salt27]

I think it's "dew" (like dew on the leafs) rather than "due" (like your library book).

I would like to demote our forum spell checker until he corrects his own name to Stand.

Thanks.

The only position lower than "spell checker" is "coma cop" and that position is already filled.   

[floydjer]

If I slip into a coma I hope someone calls a doctor rather than a cop.....

[Stan Back]

"I would like to demote our forum spell checker until he corrects his own name to Stand."

Stan is a shortened version of Stanley -- like Ray is short for Raymond.  I guess I could change it to Stanl, but dad always said, "Stan, back!"

[Jack Gifford]

Long winter?

[floydjer]

"I would like to demote our forum spell checker until he corrects his own name to Stand."

Stan is a shortened version of Stanley -- like Ray is short for Raymond.  I guess I could change it to Stanl, but dad always said, "Stan, back!"

If that is the case..I should change my screen name to "Dang it Jer"

[Bob Drury]

   Hey!  I have made a ton of post's on this site and between Stan, SS and SSS I have been chastised, bullied, thrown under the bus, held to the fire, fed to the wolves, ground by the grinder (think FARGO) for a few slip ups (take it for what it's worth) as if I give a flying rats ass.
   If you stay with it long enough, they will give up after ten or fifteen years as they realize that the goal is to keep them on their feet, grinding their collective teeth, seething in their own anger and stewing in their own pot!
                                                    Most (or mostly) Sincere,
                                                              "One Run" Bob, out.........................................
  p.s. What ever became of Mr. Green ?

[racergeo]

   Good one Bob......

[Speed Limit 1000]

   Hey!  I have made a ton of post's on this site and between Stan, SS and SSS I have been chastised, bullied, thrown under the bus, held to the fire, fed to the wolves, ground by the grinder (think FARGO) for a few slip ups (take it for what it's worth) as if I give a flying rats ass.
   If you stay with it long enough, they will give up after ten or fifteen years as they realize that the goal is to keep them on their feet, grinding their collective teeth, seething in their own anger and stewing in their own pot!
                                                    Most (or mostly) Sincere,
                                                              "One Run" Bob, out.........................................
  p.s. What ever became of Mr. Green ?

https://www.youtube.com/watch?v=F7HfMwWIJtE

[Stainless1]

Wow One run.... you're not going snowflake on us are you....  get your shit together and let's go racing.
BTW, running a little short on cash... can you lend me a $100 till my hunch back brother straightens up