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Discussion Starter · #1 · (Edited)
So you want to autocross and you know you have to pump up the tires. But you do not want to aid air to the nitrogen already in your tires. What to do? Buy an air tank (Sears has them from $50 to $100 then go to your dealer and ask if he could fill up the tank for you. I have a really good relationship with my dealer and he does it no questions asked for free whenever I need gas.
Now there will be some that will say you do not need it fine don't bother. However, for those of you like me that wants to keep the nitrogen un mixed, if the dealer will not cooperate find a local gas passer in your area to fill your tank.

My helpful tip for today.:Dance:
 

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Or you could dump the nitrogen and use air!
 
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I have a Power Tank 10lb nitrogen bottle that I use for the bus tires, 120psi/front, 105psi/rear is more than my compressor can handle. Supposed you could use one if you don't mind hauling it around.
 

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For Nitrogen?
Yup
Has been said here many of times. Most Costco's, I know the half dozen or so I can hit up in the LA area, have a fill up station outside their garage. That way anyone can pull up, and top off.

If I had to air up, I would air up using regular air. Then, after my run, air back down to my preference. Then, hit up Costco's tire center and tell then I had to use air, and would like them to refill with nitrogen. They will, and I will be done.
 

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Nitrogen is commonly used to fill racing tires, for the principal reason that it is clean - meaning free of dissolved water (aka, humidity). The objective is to have predictable, and repeatable pressure increase as the tires heat up when used on the track. It is possible for a cold tire to have some of the dissolved water drop out as liquid, and remain as liquid when the pit crew checks pressures in the morning or when the car is taken out of a cold trailer. This liquid water can evaporate when heated, dramatically increasing tire pressure above the desired hot setting. This introduces unpredictability into race preparations, which is obviously undesirable. The solution is to make sure no water gets into the tire in the first place, hence use nitrogen from a cylinder.

Most tire busters, even at race tracks, will use air to re-inflate after mounting. Or if using N2, will leave in the air that was trapped in the new tire. There is a nifty little ejector device that fits on the valve stem and uses compressed air to evacuate all the gases inside the tire after mounting. The tire shrinks up like those miracle garden hoses on TV. The tire is then re-filled with dry N2 to the desired pressure, usually higher than the likely cold setting so N2 is only being let out to set the cold pressure before going on the track.

Some people think that N2 will maintain tire pressure better than air over time, on the basis that the nitrogen molecule will not leak through porous rubber as easily as some of the constituents in air (such as Argon, and to a lesser extent Oxygen). This is a very small effect. One thing I can say for sure, use of N2 makes the tires smell very funky when they are removed from the rim.

In my opinion overkill for the street, but what do I know?

Regards, Dick Roberts
 

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Discussion Starter · #11 ·
At the autocross (which is a race of sorts), guys that do not use N2 have one gallon weed sprayers filled with water to cool their tires down after a run to get the pressures down. Now if you use N2 you chalk your tires to see how much rollover you are getting and how much pressure has built up. Say the tire roll is good at 40 pounds and the tire grew 2 pounds during the run. Then fill the tires to 38 and your tire set up is done for the rest of the day. No spraying, no checking air pressures, no filling, and releasing. As for my experience on this subject, I have raced stock cars for years to include the Florida 200 at Daytona so I have some experience on this subject. As for street use, I would not go out of my way for N2.
 

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Registered to this forum to react on Nitrogen filling.
Live in Holland, Europe, and my tire-pressure story began end 2007 when I got hold of the European formula of tyremakers , for calculating pressure for a sertain load. Googled a lot for it and learned myself Excell to make spreadsheets for it.
Now call myself tire-pressure specialist.
So wont introduce myself in a seperate topic , only react on tirepressure aand tire-choise related questions.

Yust recently figured out the Nitrogen filling and the effect of water in tire.
Found a spreadsheet with Partial pressure of water for temperature, and concluded that for lower pressures ( fi 2 bar often used in races) the extra rising of pressure when water in it is relativaly large.

If temperature in tire rises from freesing point of water to boiling point of water ( 32degrF/0degrC to 212degrF/100degrC) wich can happen incidentially by the heat of brakes transported trough the rimms to the tire inside, The partial pressure rises maximum of 14.5psi/1bar.
This is for a tire filled with 2bar/29psi that rises to about 45 psi dry , wet a lot more so 45+14.5=59.5 psi , this is for races that much difference that gripp gets lost because of the lesser deflection of tire.
For Truck tires filled with 100 psi at 32 degrF and rises to 142psi at 212degrF, wet would be 142+14.5= 156.5 psi , a good 10% higher so smaller effect on deflection so gripp.

Once made a spreadsheet to play with temperature and pressure , and originally made it for races where tire-inside air can get 90degrC/195degrF?.
Then the idea was to fil cold that low that warm it gets the same warm pressure as for 45degrC/112 degrees F wich is normal warm inside tire.
This if enaugh liquid water in tire to go over to gas to get 100% humitity of water at 212 degrF. If half of that Humidity gets 50% when 212 and pressure rising only 14.5/2=7.25 psi extra rising because of water in tire

Will give link to my motorhome calculator map in wich the pressurecalculationwithtemp-spreadsheet
https://onedrive.live.com/?cid=A526E0EEE092E6DC&id=a526e0eee092e6dc%21793
First download it to your computer by RIGHTCLICKING and then after eventual virus schan open it in Excel or same kind of programme on your computer.
From this map you can navigate my complete public map of the one/drive , that belongs to my hotmail.com adress with same username as in this forum. Much about tire/pressure.

also made a word document about that filling with normal air with all the water in it , is even better then Nitrogen. But this goes for normal street use.
If wanted I will give a copy in next post.

Mind also that if you let all the air of the tire to reduce the oxigen part, the liquid water thats on the bottom of tire stays in.
only the water as gas ( humidity ) goes out by the valve then.

Enaugh for my first post.
Greatings from a Dutch Pigheaded self declared tirepressure-specialist
 

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At the autocross (which is a race of sorts), guys that do not use N2 have one gallon weed sprayers filled with water to cool their tires down after a run to get the pressures down. ... No spraying.
N2 will not negate the need for spraying. We use water to cool the tire itself as much as possible in between runs, not solely for air pressure adjustment. I'm sure a cooler tire will help reduce pressure but with so little time between runs, it is faster to bleed down the tire with a gauge. Spraying is still required when tire temps are high.
 

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Welcome to the forum, jadatis, and thank you for that insight!
 

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It depends on the quantity of water in the air and the real temperature rise. 100C is extreme given on hot roads here in summer tyre temperatures rarely exceed 50C. It would take a large volume of water to affect the pressure in the tyre. If the compressor has a decent water/oil separator there is no practical difference. Yes the N2 molecule is larger than O2 despite the molecular weight difference however there are many many studies showing N2 is also just a load of hot air.
 
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