Nitrogen Filled Tires

[damnyankee]

First question is......Is it allowable to fill tires with nitrogen (or any other gas) rather than "air" in a stock class?

Next is.....Do you think there is any benefit to filling tires with nitrogen (or any other gas) rather than "air"?

[adam]

I have heard that some tire places fill new tires with nitrogen. I believe they do this because nitrogen is a homogeneous gas that is more temperature stable than air since that is a mixture with multiple constituants and there is a uniform pressure rise with a given temperature rise. I myself do not see this as being a super critcal facet to tire inflation assuming the proper pressure it in the tire but i guess that depends on how hot the tires will get and how accurate you want the pressure to be.

[damnyankee]

I know that nitrogen does not expand (with heat) as much as ambient air does. NASCAR uses it.

I did not see anything in the solo rulebook prohibiting the use of nitrogen.

[jbyrd]

There is no rule against nitrogen in tires.

[damnyankee]

Is there any benefit to using it for autocross?

[trdriver]

damnyankee38 said:

Is there any benefit to using it for autocross?

benefits (whereever used) would include more uniform pressure over any given heat range - due as much to the complete abscence of moisture as well as it being a uniform gas.
Is the difference noticeable? unless the air in your tires is overly moisture laden - i.e. came undried/unfiltered from a tank in a gas station or shop that rarely or never drains condensation from their tank - probably not. Remember - AIR from the atmosphere is 78% Nitrogen.

Cheers,
Jack Mc

[MiataRacing]

Just a heads up when we autocrossed in stock we looked into using nitro in the tires for the reasons noted about the heat, but someone from nationals once told us that is there is not a rule saying you can't use it dosen't mean you can. I would just be careful, more so if you run a national event. Localy I don't think anyone will protest you.

Tom

[soloracer]

Mercedes used nitrogen in thier formula one cars before the "modern era", which started in 1950.
Nitrogen is an inert gas. Another benefit not mentioned so far is it slows deteriation of rubber. While agreed air is mostly nitrogen, air still leaves 22 % to chance. As oxygen will unite with most anything, nitrogen will help maintain the integrity of the tire.
And as mentioned, Nitrogen has a negligable pressure change when acted upon by increased heat. I have observed "air" can change tire pressures as much as 5 pounds P.S.I. from a cold morning to a warm afternoon. The larger the tire, the more pressure change. We only used nitrogen in the Mclaren I maintained because small pressure changes made a huge difference in contact patch.
Hope this helps.

[Warp3]

jbyrd said:

There is no rule against nitrogen in tires.

Yes, but most of the SCCA rule categories (including stock) are based on the concept of a class of allowable mods. Thus unless a modification is somehow permitted by the ruleset, it is not legal. ...or as that concept is more popularly quoted: "If it doesn't say you can, you can't."

[hippie]

OK........
1---The main reason to use nitrogen in your tires is that it has a low moisture content. Any gas expands with heat, but water and water vapor expand much more. If you have a lot of money to spend use argon because it has an even lower moisture content than nitrogen. I think welding grade argon is 99.99% pure.
2---A small (5 lb) bottle can fill many more tires than a 5 gal air tank and it's more compact and easy to handle.
3---Based on my experience 3-5 lbs of pressure build on my first couple runs with cold tires and shop air can be reduced to 1-2 lbs with nitrogen. It doesn't matter that much, but it's easier to keep up with the pressures.
4---It is legal. Ask Rob F. or many other national drivers around here. A lot of their enclosed trailers have large bottles mounted in them. Also, how could anyone prove or disprove that there's "shop air" in someone's 5 gal air tank?

5---I never even thought of what soloracer mentioned regarding oxidation, but that's also a good reason to use nitrogen. Especially if you store tires for a long period of time.

mike

[Warp3]

hippie said:

4---It is legal. Ask Rob F. or many other national drivers around here. A lot of their enclosed trailers have large bottles mounted in them. Also, how could anyone prove or disprove that there's "shop air" in someone's 5 gal air tank?

Just to clarify, I wasn't saying that it wasn't legal. I was merely pointing out that the lack of a restriction in the rulebook doesn't always equal "legal" in the SCCA Solo rules.

[hippie]

Just to clarify, I wasn't saying that it wasn't legal. I was merely pointing out that the lack of a restriction in the rulebook doesn't always equal "legal" in the SCCA Solo rules.

Copy. That's the bit*h of interperting the SCCA's rules. I'm used to "if it doesn't say it's illegal then it's legal"

When they don't say you can and they don't say you can't........where are the gray areas? ;D